MS05000 Budget Logic Analyzer Probe Set Design

[Gandalf_Sr]

Design Aim
The design aim is for a budget LA probe for the MSO5000 that can be built to work in 2 positive voltage ranges:

1. 0.65V - 3.6V logic levels using a SN74AXC8T245 as U3 on the probe PCB - probably at 100 MHz or more (to be tested) but tested at 50 MHz.
2. 1.6V - 5.5V logic levels using a SN74LVC8T245 as U3 on the probe PCB (and other minor component differences) - tested at 50 MHz.

The official Rigol connector (PLA2216) uses expensive Op Amp ICs that can (theoretically) work up to 15V and 1GHz but they cost $400 a set ($350 if bought with the scope) and the scope LA input is only specified up to 200 MHz.

Project Status
The design is finished, the 3.3V version of the probe PCB has been built and tested at 50 MHz. I have ordered a load of PCBs so if you want a set, look at this post and PM me with what you need.  Then go and check out this post that has links to Digikey carts that will allow you to buy all the parts needed. The schematics in .pdf an BOM in Excel are here.

High Level Summary
The design uses 2 different PCBs:
1. A passive (no active components) Connector PCB that adapts from the MSO's 50-pin 0.1" header (J1) to 2 x 0.1" pitch 24-pin headers that take standard ribbon cables.
2. Two Probe Adapter PCBs that convert the sensed logic signals into LVDS which they drive into the ribbon cables.

Each probe PCB has an 8 bit voltage level translator (VLT) IC followed by 2 x 4 bit LVDS driver ICs.  The LVDS driver ICs and the output (B) side of the VLT run at 3.3V which is supplied by a 3.3V, 300 mA LDO regulator (that supply is also available for your use on the 3.3V test pin).  The input (A) side of the VLT is powered from an adjustable 0.6V to 3.9V, 100 mA LDO regulator (that supply is also available for your use on the Vadj test pin).


Probe Adapter PCB
This description is for the 0.65-3.6V version (with the 1.6-5.5V version differences shown in parentheses); the 3.3V LVDS signals these boards output are the same and any combination of probe PCBs can be attached to the Connector PCB.
Eight logic sensing leads connect to J1 feed into the A side of a SN74AXC8T245 (SN74LVC8T245) which is an 8-bit voltage level translator (VLT) that can range from 0.65 to 3.6V (1.6 to 5.5V) operating voltage. The VLT is hard-wired to make the A side the input and the B side th eoutput.  The outputs on the B side of the VLT run at 3.3V and feed a pair of DS90LV047A LDVS driver ICs that drive the LVDS signals to the Connector PCB via the 24-pin header connectors and ribbon cable.

There are 2 separate power supplies on the Probe PCB both fed by the 4V line passed from the Connector PCB:
1. A 300 mA 3.3V fixed LDO linear regulator that supplies the DS90LV047A LDVS drivers and VccB on the SN74AXC8T245 (SN74LVC8T245).
2. A 100 mA LDO that is adjustable from 0.65 to 3.6V which supplies Vadj.

A switch selects what voltage is fed to the VccA side of the VLT IC, U3; it selects between Vadj or Vext (an external voltage that you have to feed in on a pin on J1).  This allows the device under test (DUT) to be powered by Vadj up to 100 mA (the level translator IC uses uAs) or for the DUT to provide the power to VccA. The max voltage that should be fed into the Vext pin is 3.6V (5.5V) but a protection Zener diode protects the SN74xxx8T245 VccA side.  To monitor logic at voltages greater than 3.6V on the SN74LVC8T245, VccA must be sourced from the Vext pin because the Vadj supply only goes up to 3.6V (YMMV but the limit is the actual 4V level from the scope and the drop over the LDO regulator).  Note that the level adjustments available on the MSO5000 menus don't do anything as the input resolution of a 1 or 0 is related to the VccA applied to U3.

The Probe PCBs are only 2 layer; I ran impedance calculations for the 2-layer PCB and it comes out around 130 for 1.6mm FR4 and my trace widths so I think it will be OK up to 100 MHz or so.

200 series resistors (R0-R7) provide basic protection to the inputs to the SN74AXC8T245 and there are also optional 10k load resistors (R13 - R20) on each input. Care should be taken not to overvolt the inputs or U3 could be damaged.

The Connector PCB
This is 4-layer passive circuit that routes the LVDS signals coming from the Probe PCBs to the front connector on the MSO5000. The pairs of LVDS signals are length matched to <3mm and the channels are all within 10 mm of each other. The traces have been moved to be on the same side for each LVDS pair (as far as possible) and have curved traces to avoid reflections (all probably overkill for 100 MHz).

The latest schematics are attached to this post.

[Edit1] Upload of .pdfs schematics
[Edit2] 2/28/20 to reflect 5V option and protection components
[EDIT3] 3/8/2020 major update of all text to reflect design changes and build status
[EDIT4] 3/14/2020 first & second posts updated to show working status and pictures of it running
[EDIT5] 3/21/2020 updated to reflect the choices made for input protection on Probe/Connector vn1b2/1a4 PCBs
[EDIT6] 3/23/2020 updated to delete the schematics attached to this post and point to the latest ones
[EDIT7] 3/28/2020 added more detail to the circuit description
[EDIT7] 4/28/20 added link to post that has zipped schematics and BOM
[EDIT8] 5/2/20 changed VccIO to Vext to match markings on Probe PCB
[EDIT9] 5/21/20 minor changes to enhance readability and clarity

[thmjpr]

maximum logic level voltage of 3.6V (4.2 absolute max)

]

If you are saying it will be damaged when going above 4.2V, I would consider adding some resistor protection. At least to prevent the thing from being blown up, if you inadvertently touch the probe to a 5V rail say.

I would say enjoy the cruise, but yeah this is probably more interesting for you

[Gandalf_Sr]

[EDIT] Here are the pictures of the finished 3.3V version running at 10 MHz.

[Gandalf_Sr]

maximum logic level voltage of 3.6V (4.2 absolute max)

]

If you are saying it will be damaged when going above 4.2V, I would consider adding some resistor protection. At least to prevent the thing from being blown up, if you inadvertently touch the probe to a 5V rail say.

I would say enjoy the cruise, but yeah this is probably more interesting for you

It's ages since I looked at any 5V logic.  The issue I have run into recently is being able to handle sub 3.3V logic levels, this setup goes all the way down to Vcc at 0.65V.  Adding a simple voltage divider to deal with 5V logic should be very simple.

[EDIT} Keep reading as the design was enhanced to allow use of a LVC VLT IC to handle up to 5.5V logic levels.

[texaspyro]

It's ages since I looked at any 5V logic.

Supporting 5V levels wou;d be a very good thing (I'd consider essential for any logic analyzer).  There is a LOT of older 5V equipment (and Arduinos) out there that need an occasional probing.

[Gandalf_Sr]

I hear you 5-volters and have just looked at using the LV4T family (e.g. SN74LV4T125) which would allow me to range between 1.2V and 5V on the input voltage side, I've asked for advice on TI's e2e forum but the LV4T devices will use a bit more power and only work at 50 MHz max.

[EDIT] If U3 on the Probe PCB is changed to a SN74LVC8T245 and R10 made 0 then the PCB (with no modifications) can run between 1.6V and 3.9V using the onboard Vadj LDO supply or you can feed an external 5V in to run the logic at 5V levels. With this change you lose the ability to go as low as 0.65V logic levels and you will have to supply an external VccA because you can only supply VccA with up to 3.9V Vadj from the Probe PCB, and you can only go up to 50MHz (has been tested OK at 50 MHz) - That was easy

Unless TI suggest something else, we can build 0.65 - 3.6V and 1.6V - 5.5V versions of the Probe PCB on the same bare board; you can mix a 0.65V - 3.6V probe (8 channels) and a 1.6V - 5.5V probe (another 8 channels) plugged into the Connector PCB at the same time.

Note that the Vref signal from the MSO5000 is not used.  The only power supply that's used from the MSO5000 is the +4V which is fed through a 1210 component (mounted on the Connector PCB) that can be a resettable fuse or a ferrite bead inductor (or a 0 resistor); it seems to me that the MSO5000 will almost certainly have some sort of current protection on the +4V supply so my inclination is towards a ferrite bead inductor.

[Gandalf_Sr]

Update...

I have tweaked the PCB designs for the cheap LA probe hardware, the connector PCB now has all LVDS pairs routed on the same side (as much as possible) and the traces are all curves.  The probe PCB has minor improvements and both PCBs have loads of ground vias added to stitch around the edges of the LVDS signals.

I am waiting for a parts delivery from Digikey so I can check some footprints before ordering the PCBs. The passive, 4-layer (LVDS) Connector PCB adapts the MSO5000 down to two 24-pin 0.1" headers each carrying 8 channels of LVDS data.  There are 2 identical, 2-layer probe PCBs which use 8 channel voltage level translators (can be one of 2 types) feeding into 2 x LVDS driver ICs (4 bits each) per Probe PCB that drive the LVDS signals into more 24-pin 0.1" headers that feed the ribbon cables and on to the Adapter PCB which, as far as the signal path is conerned, has nothing but LVDS terminating resistors.

Each probe PCB can be fitted with one of two different voltage level translators; one allows a VccIO range of 0.65 - 3.6V and the other allows 1.6 - 5.5V; you can have one of each if you want to.

Total BOM cost for the whole setup (2 x probe and 1 x connector PCB) is about $25 in components plus the cost of the PCBs - maybe another $20.  I deliberately kept everything at 0603 and 0.65 mm pitch TSSOP (ICs with legs) so that it can be hand-assembled by those comfortable with SMT assembly.

[texaspyro]

If you have room for 0805's it makes it considerably eassier to hand assemble...

[Gandalf_Sr]

If you have room for 0805's it makes it considerably eassier to hand assemble...

0603 is my standard size for hand assembly although I do work under a stereo microscope.  I should have added that I'm trying as much as possible to maintain signal integrity and IMHO 0603 is better than 0805 in this respect (0402 would have been better still but they are more difficult to work with).

My MSO5074 arrived a week ago but has been RMAed as they sent me old stock (Cal date 3/18/2019), a new (hopefully) one will arrive tomorrow.  JLCPCB are back at full production so, once my Digikey order arrives, I can check the footprints and order the PCBs; then it will be a couple of weeks before they arrive.

[texaspyro]

I should have added that I'm trying as much as possible to maintain signal integrity and IMHO 0603 is better than 0805 in this respect (0402 would have been better still but they are more difficult to work with).

At the frequencies involved in the probe (200 MHz) the 0805 package size is totally acceptable. 

[Gandalf_Sr]

I should have added that I'm trying as much as possible to maintain signal integrity and IMHO 0603 is better than 0805 in this respect (0402 would have been better still but they are more difficult to work with).

At the frequencies involved in the probe (200 MHz) the 0805 package size is totally acceptable.

I know it's overkill but I was trying to observe the LVDS routing rules with 0.3 mm trace width/gap and then not have a massive flare when it arrives at the terminating resistor just before going to the scope connector.

Quit your nit-picking or I'll make them 01005s 

[Gandalf_Sr]

I got the Digikey order and checked some footprints, I'm glad I did as I didn't allow enough width on the headers that are side by side on the connector PCB, this is now fixed along with a few minor changes.  MY MSO5074 arrived today too and I checked the front entry space for the connector PCB, it's OK.

The PCBs were ordered today from JLCPCB, I ordered 5 connector PCBs and 10 probe PCBs; remember that a set is 1 connector and 2 probe PCBs.

Now I have to wait. I'll update the PCB views in a day or so.

[EDIT] The PCBs shipped yesterday and their system predicts they will arrive Friday 13th (my lucky day).  Sorry, still not updated any of the files.

[Gandalf_Sr]

By way of a bump and an update, DHL says that my JLC PCBs departed from Cincinnati (250 miles South of me) at 6:30 am today and they are supposed to get to me by the end of today although that sounds a bit optimistic although possible; the main freight truck will probably get to Michigan around 11 am (unless they are flying them up) and then they'd have to make it onto the actual delivery truck and to my house.  If they don't make it today, they could be delivered tomorrow.
[EDIT] seems the package got to Romulus Michigan in 2.5 hours so, unless they drove it up in a Ferrari at 100 mph, it must've flown up . Yup, it got here around noon and the PCBs look great.

I revisited the documentation on LVDS vs LVPECL and I think that LVDS running at 3.3V and driving into a 100 resistor close to the MSO5000 connector is going to drive the MSO5000 internal circuits OK, I will run a test before I fully populate the PCBs as it may need a 120 resistor - I really hope this is going to work as it could be a show-stopper; I should have tested first but I didn't. Sigh!
[EDIT] I asked over at the other real LA teardown thread and dug into the driver datasheets; the real LA probe set uses LMH7322s which are hooked up, with 2.5V for Vcco, which makes them run with LVDS-compatible outputs with H = Vcco - 1.0V and L = Vcco - 1.4V (centered on 1.2V) which is LVDS-compatible. My design uses DS90LV047As which have LVDS outputs which should be fully compatible with the MSO5000 inputs - we'll see.

I was planning a fun trip to Chicago with my Brother next week but we cancelled due to the COVID-19, weld-yourselves-into-your-houses, panic.  So now I'll be able to work on this unless I get some paid work to do.

[Gandalf_Sr]

IT's ALIVE!!!!! BWAHAHAHAHAHAHAAAA

Go back and see the second post for updated pictures of it running (at 10 MHz).  I only built the 0.65-3.3V probe board so far and the input protection Zeners were missing from my Digikey order so it's running without them for now.

I'm VERY happy with the results so far.  First 8 channels are all the correct polarity and the LVDS signals are clearly working at least at 10 MHz, I tested channels 0-7 so far.

[Sighound36]

Would just like to say this thread is what really good about this forum sharing knowledge and experiences top stuff  Gandolf_Sr.

I just do not have the time to do these sorts of projects at the moment and its great to see 

Promise I will do an update on the 8000 thread soon.

[joeyjoejoe]

Very cool, nice work! 

[Gandalf_Sr]

Total cost for components for 2 probe boards and 1 connector board (including 2 x 6" ribbon cables) is $35.28, if I order say 50 of the PCBs my guess is $1 each for the probe boards and $2 each for the connector boards.

Still doing more testing but here's another picture of the 2 different probe PCBs, the one on the left with the red LED is the 1.6-5.5V version and the one on the right with the green LED is the 0.6-3.6V version.  I triggered it from D4 with a serial signal while feeding a 50 kHz square wave into the other probe board on D11 and D14, the yellow trace is analog Ch1 showing the 50 kHz signal.

[Gandalf_Sr]

Here's an picture of the connector PCB (before I added all the termination resistors).

[EDIT] Did some high frequency tests on the 0.65-3.6V probe PCB running at 3.3V with a 50 MHz square wave from my DG4202; it looked OK but there was an occasional 1 nS jitter on all channels.

I wonder if that was the signal generator?

[Gribo]

What part did you use for the 50 position 0.1" header?

[Gandalf_Sr]

What part did you use for the 50 position 0.1" header?

This one https://www.digikey.com/product-detail/en/sullins-connector-solutions/SFH11-PBPC-D25-ST-BK/S9201-ND/1990094

[Gandalf_Sr]

While the vn 1a boards seem to work just fine, I have a tweak in progress to fix very minor issues, like the adjustable voltage control pot works backwards.  I have a few other tweaks to consider too.

If I order new vn 1b PCBs I can add to the order if anyone's interested? PM me if you want a set.  I'll update the schematics and add the BOM later this week.

[thmjpr]

Here's an picture of the connector PCB (before I added all the termination resistors).

[EDIT] Did some high frequency tests on the 0.65-3.6V probe PCB running at 3.3V with a 50 MHz square wave from my DG4202; it looked OK but there was an occasional 1 nS jitter on all channels.

I wonder if that was the signal generator?

Nice work.
You can see in the specs the LA sample rate is 1Gs/s, so 1ns jitter may be expected.

[Gandalf_Sr]

Here's an picture of the connector PCB (before I added all the termination resistors).

[EDIT] Did some high frequency tests on the 0.65-3.6V probe PCB running at 3.3V with a 50 MHz square wave from my DG4202; it looked OK but there was an occasional 1 nS jitter on all channels.

I wonder if that was the signal generator?

Nice work.
You can see in the specs the LA sample rate is 1Gs/s, so 1ns jitter may be expected.

Thanks, so that suggests that the jitter is not a problem of my design    In reality, there are not many serial data systems that I've designed that run at more than a few MHz so this is likely a non-issue.  My aim was to make it cheap and functional and I think I achieved that.

One thing I haven't found yet is where in the menus I can align the analog and digital signals in time - I thought that was somewhere in the menus?

[NoisyBoy]

Nice, love reading all the great progresses you are making.

[Gandalf_Sr]

Question on Front End Protection
So the probe design is working fine at 50 MHz but I had originally designed in some protection on the front end (see picture).

J1 is the probe input connector and R0-R7 are 200 series resistors and the results I've posted so far are just with those series resistors fitted.

The 3.6V dual Zeners (D2-D5) arrived yesterday and I fitted them but they clearly affect a 10 MHz 3V square wave so they are not going to work and I took them off.

I tried adding terminator resistors R13-R20 but they don't seem to have any affect at all and a TI engineer on the e2e forum thought I didn't need them.  However, the datasheet for the SN74AXC8T245 warns that it shouldn't have floating inputs but the chip seems just fine with just the series resistors and, with nothing connected, the detected level registers as a zero.

I have various FET scope probes that have warnings about maximum voltage.  The schematic shown is for the 3.3V probe version (the 5V version uses an SN74LVC8T245 as U3) and the absolute max input voltage for the SN74AXC8T245 is 4.2V according to the DS so a 5V logic input could fry it (with the LVC version it's 6.5V but the minimum Vcca voltage is limited to 1.65V).  I don't work with 5V logic but I did build a probe PCB that has the 74LVC part in case I ever needed to.

Before I tweak and make V1b of the probe PCBs, what do you guys think I should have at the front end?

1. Just the series resistors and provision for the termination resistors on the PCB so people can populate if they want - you fry it, you change U3.
2. Option 1 but with series and termination resistors fitted - might offer some protection but changes input impedance to 10k
3. Something else???

[electricMN]

How about option 1 but just offer the board blanks for sale if someone wants to assemble the boards themselves.

[thmjpr]

AZ23C3V6 seems to have a capacitance in the ~100pF range, which is not too high but definitely much lower capacitance diodes are available.

Its hard for me to see why you wouldn't want the high value pulldown resistors. If the pins are floating in the air and reading 0V thats one thing, but what if you are probing a broken trace or similar? It could give misleading levels if its not lightly loaded.

Input clamp current is stated as 50mA max, so if you can stay under that it would be good. 5V -> 200R -> (3.3V + 0.6V) = 6mA, seems alright.
You might consider a 3.3V TVS on the supply rail so the ICs ESD diodes have something to dump to (I'm assuming here they are present, but datasheet only mentioned Vi < 0 so not sure). If the individual line zeners are not used. I know I've said it before, but I fully expect 5V to be applied on those inputs.

[Gandalf_Sr]

I'm struggling to pick the right voltage for a TVS diode to protect the 3.3V supply rail (Vccb).  I found the PESD4V0Y1BSF but, although the min breakdown voltage is 4.2V, the typical is 6.2V, and the max is 8V.

Any comments on what a suitable TVS diode should be?

[MarkL]

...
One thing I haven't found yet is where in the menus I can align the analog and digital signals in time - I thought that was somewhere in the menus?

I don't have this scope, but according to the User Manual it's in the channel menu.  Their example for Channel 1:

Press 1 --> More --> Ch-Ch Skew, rotate the multifunction knob or use the numeric keypad to set the desired delay calibration time. The available range of the delay calibration time is from -100 ns to 100 ns.

[Gandalf_Sr]

OK, I'm close to ready to order the new PCBs although the Connector PCB is unchanged.  Attached are new pictures and I'll follow up with another post with the BOM and schematics for both PCBs.

I took out the pesky protection diodes on the input lines and placed new 10k resistors to ground on each input line.

[EDIT] I added a protection diode on the 3.3V side of the voltage level translator as requested.

I have 4 people who've asked me for PCBs, tv84, lodkolven, and electricMN - you guys will each need a Connector PCB but let me know if you want something different from the basic just 2 probe PCBs; you will need 2 to have 16 channels and you may want 3 so you can have 2 x 3.3V versions and 1 x 5.5V version.  Let me know by PM.  To cover my costs is going to be something like $20 for 3 PCBs including shipping - have ordered extras to cover the inevitable late-comers.

[Gandalf_Sr]

BOM and schematics attached in zip file

[EDIT] If anyone wants changes, speak now or forever hold your peace.

[Gandalf_Sr]

I have decided that I will define a PCB set as 1 Connector PCB and 3 Probe PCBs and I will order them in that ratio 1:3

You can still add extras but the main idea is that, if you mainly work on low voltage stuff, you can make 2 x 3.3V Probe PCBs and 1 x 5.5V Probe PCB.  Remember that any Probe PCB can be connected to either of the 24 pin headers on the Connector PCB as the 8 channel signals coming out of the Probe PCB are the same i.e. 8 pairs of 3.3V LVDS.

The 3.3V Probe PCB can handle any logic voltage level between 0.65V and 3.6V, the 5V Probe PCB can handle any voltage between 1.6V and 5.5V but, if you want to run a 5V Probe PCB at >3.9V, e.g. 5V, you will need to feed the logic voltage into the Vext pin and set the switch to Vext; the current drawn from Vext is almost zero i.e. low single digits uA.

There are only 3 components different on a 5V Probe PCB and they are all detailed in the schematic and BOM attached a couple of posts above.

[Gandalf_Sr]

I'm going to make 2 small changes to the probe PCB before ordering...

1. The test point marked Vref that is fed by J2 pin 1 does not carry Vref from the Connector PCB (which I was originally intending to do), it's just ground so its incorrect to label it 'Vref'.  I think it would be useful to have a +3.3V test point (the output from U4) which is capable of supplying 0.3A or the limits of the MSO5000 4.1V supply - a kind of fixed +3.3V mini power supply.  So the test pin marked 'Vref' will change to '+3.3V' and J2 pin 1 will be connected to the ground plane.

2. I'm going to add a do-not-populate resistor from Vcca of U3 to ground; I've found that U3 mysteriously seems to operate even when the switch is set to Vext and there is no Vext connected!  I suspect that this is because the switch is cheap and has an open resistance of maybe 1M (I've tested it) and the AXC version of U3 draws so little current from Vcca (1uA ish) that it gets enough via the open switch to operate!  My design intent was to use the feature of U3 that, if either Vcca or Vccb is <0.6V, the IC goes into disabled, high impedance mode so a 100k resistor from Vcca to ground should cure this issue even though it would draw an additional current of approx 10 uA.

Any other ideas or requests?  Need them PDQ guys.

[ebclr]

I'm interested in a full kit including ALL components, Can you do that?

[Gandalf_Sr]

I'm interested in a full kit including ALL components, Can you do that?

Not really, I could but it would be way more work for me than it's worth.  I had thought about the major components, ICs, connectors, and ribbon cables, so there could be at least the economy of buying 10s instead of 1s but I don't want to be messing around putting 3 x 0.1uF 0603 capacitors in a marked bag on their own.

[Gandalf_Sr]

About to place the PCB order, here's the (slightly) updated probe PCB

[joeyjoejoe]

Not really, I could but it would be way more work for me than it's worth.  I had thought about the major components, ICs, connectors, and ribbon cables, so there could be at least the economy of buying 10s instead of 1s but I don't want to be messing around putting 3 x 0.1uF 0603 capacitors in a marked bag on their own.

For a while, with megadesk (https://github.com/gcormier/megadesk) I would use masking tape to tape the components to a piece of paper that had the values printed out. But these were 1206. Resistors would all be together since you can read the values, but caps would be taped separately with their own text/header.

In the end, now people are only ordering fully assembled boards, I think I've probably only sent 5-10 kit orders. I still have the listing up for parts-kits but I might just take it down, as I always try to have 5 sets of loose parts on hand which is just a waste.

I think if you offer all but the jelly beans parts in a kit, that might still have some value - anyone building this for an above entry level scope should be comfortable ordering the jellybean parts from wherever

[Gandalf_Sr]

I'm setting up a BOM in the Digikey system for all the parts needed, I think there's a way to allow people to order the BOM, I will check with Digikey tomorrow.

I ordered 100 Connector PCBs and 300 Probe PCBs and made them all blue and ENIG (Electro-plated Nickel Gold) finish as it was not much more, it never goes bad, and it's much easier to solder.  It's also EU compliant as far as ROHS is concerned. Also, because ENIG is going to be put in with higher-end orders, I've noticed that the finish tends to be better e.g. legibility of the silk screen.

[electricMN]

I'm setting up a BOM in the Digikey system for all the parts needed, I think there's a way to allow people to order the BOM, I will check with Digikey tomorrow.

....

You can put all of the items in a cart and share the cart with anyone via a link to the cart. When I was still working I did this all of the time. Fill up the cart with the parts needed and send the link to the buyer. It worked out really well for both of us.

[Gandalf_Sr]

OK, here are some Digikey cart share links. These DO NOT INCLUDE THE PCBs NOR DO I GET ANY MONEY FROM DIGIKEY.

1. Share for the parts to build 1 Connector board.

Notes: this cart includes the ribbon cables and has some choices that you need to address...

There is a PTC for P1 which should work fine but, if you want to load the 3.3V supply much (>150 mA), you should consider the ALT P1 part instead which is a ferrite bead.  BOTH are in the cart. They are not much money so you can leave both in the cart or just delete the one you don't want.

You need to pick whether you want 6" or 18" ribbon cables, BOTH are in the cart.  I've only used the 6" ones so far in my testing and they are the ones in the pictures.

2. Share for the parts to build 1 x 3.3V Probe board [Edited] There were 2 U5's in cart, now fixed

3. Share for the parts to build 1 x 5.0V Probe board [Edited] Two U5's and D1 now Red, R12 330R

I think that what you will have to do is create multiple carts and then go to their combine cart feature (Google it).

Remember you will need 1 set of parts for the Connector PCB and a Probe set for each Probe PCB; you need to choose what voltage you want each Probe PCB to be, 3.3V or 5.0V.  I made the 0603 LED Green/Red for the 3.3V/5.0V probe PCBs and this is reflected in the Probe cart links plus R12 is 270/330 .

The designation of the components will be printed on the bags you receive e.g "J1,J2", if it's prefixed by "CONN_" it's a part for the connector PCB eg "CONN_J1"

Let me know if it's broken or something is missing or wrong.

[Gandalf_Sr]

I have ordered some spare PCBs so, even if you didn't contact me before, PM me and tell me what you need.  I'm suggesting $20 to cover costs plus shipping and handling for one set which I define as... 1 x Connector PCB and 3 x Probe PCBs (so you could build 2 x 3.3V probe PCBs and 1 x 5.0V probe PCB - the PCB is the same for both voltage variants).

I also ordered enough components to build 5 Connector PCBs, 8 x 3.3V PCBs, and 2 x 5.5V PCBs and I may build some up because, well, Coronavirus lockdown.

[Gandalf_Sr]

Here's an update.

The PCBs are in production now, the 4-layer Connector PCB is stated as 8 days to build (the Probe PCB is 6 days) and I paid for DHL shipping so I'm estimating April 6 for the boards to arrive with me.  They are blue soldermask with white silkscreen and ENIG (gold plated) finish - i.e. lead free.

Both the Connector and Probe PCB have a few components on the underside.  This was done with the assumption that they would be hand-built so apologies to those intending to make solder screens.  The Connector PCB has 1 x 1210 component on the underside and the Probe PCB has about 9 resistors and 1 capacitor, all 0603, on the underside.  I think it would compromise signal integrity if I tried to put all components on one side for the boards; I have tried hard to have signal lines running with nothing but a clean ground plane on the next adjacent layer.

I will do a full write up on hand-assembly with tips.

[Gandalf_Sr]

OK, I'm getting multiple requests for PCBs via PM which is fine but I need to clarify and simplify things for you guys and me.

There's only 1 Probe PCB design, you put slightly different components on it (e.g. an LVC voltage level translator) to make it into a 5.5V version vs a 3.3V version.  The voltage range that each version will handle is as follows:

3.3V version handles logic Vcc voltages of 0.65V to 3.6V (absolute maximum Vcc is 3.6V and a '1' can be Vcc+0.2V max)
5.5V version handles logic Vcc voltages of 1.65V to 5.5V (absolute maximum Vcc is 6.5V and a '1' can be Vcc+0.5V max)

There is only 1 Connector PCB design; it has no active components but is 4-layer to handle the LVDS signals as well as possible

To have a complete setup to analyze 16 channels you would need 1 x Connector PCB and 2 x Probe PCBs, these are bare PCBs and you will need to buy and solder the components to them (see post above with Digikey cart links). You also need ribbon cables to connect the Probe boards to the Connector PCB and these are included in the BOM/cart link for the Connector PCB (note 2 x 6 inch and 2 x 18 inch cables are in the BOM, unless you want both, you should remove one pair to save cost).

So I've been asked for various combinations of PCBs so I need to set some standards... I have defined a 'SET' as 1 Connector PCB and 3 Probe PCBs - Why 3 you ask?  Because, if you mainly work with 3.3V and low voltage logic, you could build 2 x 3.3V Probe PCBs and be able to run 16 channels at low voltages e.g. 1V plus you could build 1 x 5.5V Probe PCB and mix that in when you wanted to analyze 5.5V logic.  If you really want to, you can build 2 x 3.3V and 2 x 5.5V Probe PCBs giving you the ability to analyze 16 channels at any voltage within specification so I have defined a SET+1 which is 1 x Connector PCB and 4 x Probe PCBs but, for most people, I suspect that 3 Probe PCBs is fine.

So here's what you can ask me for...
A SET =  1 x Connector PCB (the one that plugs into the scope) 3 x Probe PCBs (the ones that have all the ICs on them)
A SET+1 = a SET + 1 extra Probe PCB

I am not trying to make a business out of this, it's a sort of Covid-19 project that killed time for me (lots of time) and I'm already $100s out of pocket with orders for prototypes, shipping, components etc.

I will sell a SET for $20US shipped to the USA. I will sell a SET+1 for $25US shipped to the USA.  You can also buy the following multiples:
Two SETs
Two SET+1s
One SET and one SET+1

And I will reduce cost by $7US for the combined shipping e.g. two SETs will be $20+$20-$7=$33.  If you want more/different than these offerings, please PM me and I will try to help.

I will ship overseas but it will be the actual cost of shipping + cost of PCB sets required and, if there's no tracking, it will be sent at your risk.  In the US I will use Priority Mail which come with a standard $50 insurance coverage.

PM me what you want and I will respond with cost estimate and PayPal info.  I do not expect to receive the PCBs from the manufacturers until around April 6th.

[Gandalf_Sr]

I spotted errors in the Probe PCB Digikey saved carts which I've corrected in the previous link, the biggest error is that there were 2 x U5s LDOs.  The LT3060 is expensive but it's one of the few LDOs I could find that went down to 0.6V output.

Some here have asked for the stencil files for the new PCBs so they are attached below.

[electricMN]

I spotted errors in the Probe PCB Digikey saved carts which I've corrected in the previous link, the biggest error is that there were 2 x U5s LDOs.  The LT3060 is expensive but it's one of the few LDOs I could find that went down to 0.6V output.

Some here have asked for the stencil files for the new PCBs so they are attached below.

Shouldn't item 6 in the connector board cart be a right angle connector? I believe this is the connector that plugs into the MSO5000 LA port. Or am I mistaken?

[Gandalf_Sr]

I spotted errors in the Probe PCB Digikey saved carts which I've corrected in the previous link, the biggest error is that there were 2 x U5s LDOs.  The LT3060 is expensive but it's one of the few LDOs I could find that went down to 0.6V output.

Some here have asked for the stencil files for the new PCBs so they are attached below.

Shouldn't item 6 in the connector board cart be a right angle connector? I believe this is the connector that plugs into the MSO5000 LA port. Or am I mistaken?

No the part specified is correct.  It fits like the pictures show, you have to bend the pins towards each other very slightly.

[TK]

you can specify a different thickness of the PCB before ordering to match the separation of the pins to avoid bending them and have a tighter fit.

[Gandalf_Sr]

you can specify a different thickness of the PCB before ordering to match the separation of the pins to avoid bending them and have a tighter fit.

Thanks but the PCB would have to be 2mm thick, just 0.4 mm more so the pins only need to be bent down 0.2mm per side.  As you can see from the pictures, it's not really even noticeable and has been tested at 50 MHz.  I just used a ruler to bend the pins in ever so slightly.

I suspect that would be doable if I was ordering 1,000s but I wasn't - plus my impedance calculations were based on the standard stackup for a 1.6 mm thick 4-layer PCB.

[Gandalf_Sr]

Both boards are in production and show progress

Attached is my first cut at the build notes.

Newer V2 build notes are here

[Gandalf_Sr]

Status update.

The 4-layer Connector PCBs are showing 12% completion.
The 2-layer Probe PCBs are showing 60% completion, they are at the ENIG stage.

I'm writing a user guide for a running system.

I'm considering a 3D-printable CAD design for a small plastic shield that will clip to the underside of the Probe PCB so they don't short against each other when there are 2 plugged in side by side; I might also do one for the connector PCB.

I've been checking some things too.  The absolute maximum Vcca or Vccb that the 3.3V version (AXC chip) will take is 4.2V and the Vadj should never exceed 3.9 so that looks pretty safe.

Also I've been giving some thought on 3.3V vs 5.0V versions of the Probe PCB; which one should you build?
If you think you will never want to test logic at less than 1.6 volts but want to test 5.0V stuff then you should build the 5.0V version of the Probe PCBs.
If you think you will want to test logic at less than 1.6 volts then you should build the 3.3V version of the Probe PCBs but probably build a 5.0V version too - both can handle 1.6V - 3.3V which is 99% of what I do.
On paper, the 3.3V (AXC) voltage level translator can go up to 200 MHz but the 5.0V (LVC) is limited to 50 MHz (I tested it yesterday and it works fine at 50 MHz).
A small downside of my 5.0V design is that the vn1b3 Probe PCB can't supply more than 3.9V to the board under test so a 5.0V logic board has to feed Vcc into the Vext pin of the logic header - this isn't really that big a deal and the current consumed by this pin is almost zero (a couple of uAs) so it's more a voltage reference than a supply. This could be 'fixed' by adding a small step-up regulator but I think that's taking things too far.

[lodkolven]

Perhaps take the 5v supply from the USB-port on the MSO5000 ?

[Gandalf_Sr]

Perhaps take the 5v supply from the USB-port on the MSO5000 ?

Quite a good idea.  I'll add it to suggestions for V2.

[free_electron]

many level translating buffers do not like it when one of their sides is left unpowered.
last time i made a 'universal input' probe i used a simple opamp with strong output drive capability to power the input side.

essentially put an opamp like  a TS921 or TS951 ( that can drive 40 or more milliamp on its output) in unity gain. the output feeds the power rail of the level shifter
the input of the opamp is protected with tvs diodes and sent to the IO_SENSE pin of your probe.
a 1 meg resistor comes from your internal 5 volt rail to the opamp input as well.

So : if you do not attach anything to the SENSE line the level shifter gets 5 volt ( the opamp sees 5 volts through the 1 meg resistor )
if you wire the SENSE line to the power rail of the circuit under test the opamp will simply follow that rail voltage , so the level shifter gets the voltage of the circuit under test.

[Gandalf_Sr]

I like the 1Meg resistor to a 5V power rail idea (except there is no 5V power rail - but I could steal one from the USB connector) idea but the datasheets for these voltage level translators (VLT) specifically say that, if either Vcca or Vccb goes below a specific voltage, they go into disabled high-impedance mode. In my latest Probe PCB revision vn1b3, the one that's being manufactured right now, there's provision for a 100k resistor from Vcca to ground to specifically disable the VLT if there's no Vcca voltage applied.

Again, good ideas for revision 2 but I guess people can easily modify vn 1b3 if they want to try that out.

[Gandalf_Sr]

Here's a 3D printable Probe PCB protective back I designed today. Enjoy

[Gandalf_Sr]

Here's a photo of two Probe PCBs fitted with the 3D-printed protective back.  It snaps on and protects the underside from shorts.

[Gandalf_Sr]

Both PCBs are now at 94% on some mystery step 16...  Looks likely they will ship soon.

[EDIT] They shipped today (3/31/20) and are scheduled to arrive Monday April 6th.

[Gandalf_Sr]

Update...

The PCBs shipped REALLY fast by DHL, they are on the truck for delivery to me by 8pm today April 2nd!

Still have plenty of spare if anyone wants a set.

[Gandalf_Sr]

Update.  I got the new ENIG PCBs from JLC and they look great. 

I wanted to make sure all was well before I shipped PCBs out so I made up a 5V Probe PCB with all the changes (10k parallel resistors, 100k pulldown on Vcca, protection Zener on 3.3V rail)  and a new Connector PCB and tested at 50 MHz, all seems fine.  Here's a couple of pictures.  You'll see that the new Probe PCBs have a little white silk screen rectangle to write the voltage version on.

Given the state of the lock-down, I didn't want to go to the Post Office so I ordered Priority Mail padded envelopes from USPS (free) but they haven't arrived yet; as soon as they do I will ship out to those who have PMd me (and paid).

[EDIT] If you're building a set and are looking at my pictures below, be aware that the connector PCB is sitting face down in the picture of the 3 PCBs - pin 1 of the 24 pin connectors that take the headers for the ribbon cables has a square surround so, as you can see, if the Connector (top) board was flipped over left-to-right, the square pin 1 would be bottom right, matching the 24 pin headers on the Probe PCBs.

[Gandalf_Sr]

People who've sent me money were sent PCBs today by Priority mail, 2 or 3 days to get there depending on how far away from Michigan you are.

I'm going to try to figure out how to send overseas in small envelopes; bear with me.

[Gandalf_Sr]

Here's an updated (vn2) set of build notes.

[EDIT] OK, who spotted my (ahem) deliberate typo in that I run my soldering iron at 28 degrees C?  It should be 280 C.

[Gandalf_Sr]

bigboss59

I am trying to send you PMs but it tells me your inbox is full.  FYI, I can ship to France. 

For others, I have figured out how to send to France, Sweden, Portugal, UK, Australia for a reasonable rate (with no tracking or insurance) so I can send PCBs for the prices I already stated.

The USPS web site lists countries that they will not ship to at the moment but the above are not on that list.

PM me if you're still wanting PCBs.

[Gandalf_Sr]

Some of you will be getting the bare boards soon, here's a few notes on the circuit that may come in useful...

Connector PCB
Align J1 before soldering then solder just 1 pin and check it's straight. IF IT ISN'T STRAIGHT, DO NOT TRY TO BEND IT STRAIGHT or you will lift the pad.  Heat the 1 soldered leg and realign. Once it's aligned properly, solder the other legs.

Probe PCB
Be careful fitting VR1. I over-temped one and it was damaged and gave lumpy control of  Vadj.  Best practice is to turn VR1 upside down and tin the bottom of the leads; then tin the 3 pads on the PCB and carefully sweat it down 1 leg at a time.

Protection circuits.
PTC on the Connector PCB
There's a positive temperature coefficient (PTC) device on the bottom side of the connector PCB.  The Probe boards draw all their power from the +4.1V supply via the PTC but PTCs have a fairly high resistance and using one will limit how much current you can draw from the downstream +3.3V (300 mA max limit of the LDO per Probe PCB) and Vadj (100 mA max limit of the Vadj LDO per Probe PCB) supplies - so, in theory, you could draw 800 mA total from the MSO5000 which you would never achieve using a PTC. Also, I don't know what the current limit is that can be supplied by the MSO5000 4.1V line; the PTC will limit total current to under 500 mA. However, if you put the listed ferrite bead on the connector PCB in place of the PTC, you will get whatever the MSO5000 can supply.  I've tested that the LA works with both a PTC and a ferrite bead but I haven't done limit tests yet.

Probe PCB Overvoltage Protection
D2 is a 3.9V Zener on the 3.3V rail, if the 3.3V rail is taken above around 3.6 volts (should never happen) this Zener will ground the 3.3V supply.
D3 is a 3.9V Zener connected to the Vext pin via R8, a 47.7 Ohm 0.25 Watt resistor.  If you're building the 5V version, D3 is a 5.6V Zener and may trip as low as 5.3 volts which may cause issues if you're using an over-voltage 5V logic input at say 5.2V (check the range in the diode's datasheet). If this is a problem, you can either put a higher voltage Zener as D3 or leave D3 off the PCB and have no protection other than the 47.7 Ohm resistor.  If you want to supply the device under test with more than a few mA of current and you're using Vext to supply the DUT, be aware that R8 will reduce the supplied voltage; however, you can supply the device under test from the Vadj or +3.3V pins (device shutdown limits are 100 mA or 300 mA) on the 3-pin header just above the switch.

R21 (100k Ohms)
R21 is provided to pull Vcca down to zero when there's no power.  I found that Vcca would stay on for seconds at a time without R21, probably because the voltage level translator (VLT) IC draws so little current.  The ACX (3.3V) version of U1, the VLT, is most susceptible to this effect although it's not really an issue, I just didn't expect U1 to operate with no Vcca supplied.

[NoisyBoy]

Hey Gandalf_Sr,

I have been watching your project since your inception during your cruise, but I did not have time to participate.  Nice work and that was done really fast!  Great work and thank you for all your kind contribution to the community.  I am many here will benefit from it without having to pay the high price for the Rigol probe.

[Gandalf_Sr]

Thanks, that last cruise was just in the nick of time before the whole shut down kicked in.  I'm still getting requests for PCBs.

[ForceFed]

PCBs and Digi-Key order have arrived. Thank you again!

[Gandalf_Sr]

ForceFed and others,

Ask here (or send me a PM) if you run into any problems, I think the design is good but I'm not infallible.

[Gandalf_Sr]

bigboss59 keeps PMing me asking if I got his PMs. His mailbox is full and I can't send him replies, if someone can contact him and tell him that, I would appreciate it.

[Gandalf_Sr]

Apologies to those non-US people who've paid me for the PCBs; I haven't shipped them yet because the $1 stamps I ordered a week ago from the US Postal Service STILL haven't arrived and their stupid rules won't let me use the click-n-ship system to print postage from my PC system for overseas mail.  I will see if I can talk my wife into allowing me out to the Post Office to buy them over the counter.

[TK]

If you have paypal account, you can use it to print postage domestic and international http://paypal.com/shipnow

[Gandalf_Sr]

If you have paypal account, you can use it to print postage domestic and international http://paypal.com/shipnow

Thanks, but not for the photo-mailers that I need to use to get under the wire for non-exorbitant mail charges.

[TK]

You can ship flat padded envelopes to Europe for around $4 to $5 using paypal shipnow

[Gandalf_Sr]

You can ship flat padded envelopes to Europe for around $4 to $5 using paypal shipnow

I tried to do that today, my PayPal account seems to be broken, it won't let me quote for a flat rate envelope as it says I have no credit cards associated with my account (I do), I tored to call customer service; after going through their menu system, I got a message saying that due to Corona virus, their customer support is closed and then hung up on me.

Mail man has been, no stamps. Fuck it I'm going to the Post Office.

[TK]

Sorry to hear it is not working, I used it last week and was OK.

[Gandalf_Sr]

Sorry to hear it is not working, I used it last week and was OK.

No problem and no need to apologize, I know you're only trying to help; it's just so frustrating that I can't do something as basic as buy stamps or postage and every basic service organization has no customer support operating, I tried to call USPS to say "USPS yer c****s, where's me f###ing stamps?" (plagiarized from Kevin bloody Wilson) but they too had a message saying that, due to Corona Virus, they have no customer support operating.

Wife got upset when I said I was going to the Post Office and put her foot down with a firm hand.  I'm just going to stick umpteen Santa 'forever' stamps on each package, they're supposed to be worth 55 cents each.

[WattsThat]

Yup, forever stamps = $0.55. IMO, the more stamps on the parcel, the better it looks.

Some PO trivia: My local PO clerk does that for fun at the end of the day, using up every denomination of stamp in her drawer to make up the cost of shipping on parcels she has processed. Stamps are treated as cash and this saves her from having to count stamps at the end of the day to cash out the drawer. I’ve seen her “artwork” cover every square inch of the top of the parcel with the exception of the address label and the routing bar code.

I’m told the optical scanners that read the routing bar codes also read the monetary value of the stamps along with the weight and check for sufficient postage. Seems some senders would routinely short the postage cost for priority mail and other things under 14 ounces or whatever the weight is these days that has to be handed to a clerk rather than just dumping the parcel in a mailbox.

Ps: just waiting on my DigiKey order as my boards arrived yesterday, thank you very much.

[texaspyro]

I once had several dozen sheets of various 3 cent stamps from the 1930's.  They could be bought for 10% less than face value (they had no collector value) and were quite beautiful with engraved printing.   I used them when postal rates went up 3 cents and had a lot left over.   They made for a very impressive envelope when used for the full letter rate.

[oPossum]

I tried to do that today, my PayPal account seems to be broken, it won't let me quote for a flat rate envelope as it says I have no credit cards associated with my account (I do)

The shipnow link used to work without having a PayPal balance, but several years ago it stated giving the error message. It's not your account, it is a change they made.

You can do first class parcel with the stamps.com free trial. You must cancel the free trial within 30 days or it isn't free. Deceptive and stupid but that's the way it is.

[bigboss59]

Oh sorry about that !
I wasn't expected the mailbox can contains only 5 message

Now it's empty you can finally reply to me

THanks for all

[Gandalf_Sr]

Has anyone I sent the PCBs out to built their LA probe set yet?  Pictures please!

[WattsThat]

Just finished. Only built one each of the logic boards for starters, I have no idea why I did that. Had to get out the microscope, *%^@#&!#! fricken 0603's. The only thing I did wrong was installed the red LED backwards, thankfully I had a replacement as it went flicking off into who the hell knows where.

Thank you! Now I have to learn how to use my scope (in LA mode).

[Gandalf_Sr]

Looks really nice WattsThat!  Thanks for posting the pictures.  Uner my microscope, 0603s look HUGE

[WattsThat]

Yeah, they were ginormous in my scope as well but it was because I had the 20x eyepieces in, had to put in the 10x 

I didn’t think about assembly order and followed your notes, I think for the next set of boards I’ll install U5 first, then the caps around it, especially C11. It was a little tight in there... I use a big tip as well, 1/4” Pace knife tip and it was, well, difficult.

Surprisingly, I had some issues with the EING solderability, especially just on U1,2 and 3, after the first board gave me fits, I pre-tinned the pads and then cleaned off with solder-wick, then it was easy. I also had issues with the thermal vias on the gnd pins of those chips, had trouble getting things to flow, probably just my tip temp being too low. Maybe that was the issue altogether, dunno, never had issues like that before with that finish.

All in all, it was very rewarding and I guess I saved about $300, all said and done. Just need to order the balance of the parts and finish the other two boards, have plenty of time these days as I’m on a week, off a week at work until the end of June. Damn virus. Half salary too. But, there’s no excuse not to get some projects done. Time, I’ve got, right now.

Edit: now that I look at the photos of the boards, I can see where I lifted bits of the solder mask on U1/2/3 on the 5V board which was the first board I did. That was from all the horsing around with wick trying get a good flow on the pins.

[Gandalf_Sr]

When you're doing solder wicking, you need to crank up the temperature a bit, I run at 300 C. The last thing you want is the solder on the wick sticking to legs and pads as you pull it away.  Anyway, it looks like you got it all working.

I'm the same here work wise (although I work for myself - from home), my clients take 2 or 3 days to answer simple questions so I doubt I have 15 hours a week billable, and then they have to pay me!

I had a client last year that left me unpaid for almost $10,000 - I doubt I will see that ever.  I have 80 of their PCBs - assembled by CM - but they aren't seeing any of them until I get paid.

Selling stuff on eBay is also frustrating, they hang onto my money for weeks and then charge me 10% for the privilege

[electricMN]

Has anyone I sent the PCBs out to built their LA probe set yet?  Pictures please!

Haven't started yet. Been sick for the past couple of weeks. Not coronavirus, thankfully. BP issues which seem to be resolved now. Finally getting some spunk back so will probably tackle those boards this week. I'm finishing up building a 40m ham radio.

[Gandalf_Sr]

Has anyone I sent the PCBs out to built their LA probe set yet?  Pictures please!

Haven't started yet. Been sick for the past couple of weeks. Not coronavirus, thankfully. BP issues which seem to be resolved now. Finally getting some spunk back so will probably tackle those boards this week. I'm finishing up building a 40m ham radio.

@electricMN
Sorry to hear you've been sick, hope you feel well now.  These are strange times when we're all stuck at home with SO many things to tinker with.  As I move towards retirement, it occurs to me that I need to be more disciplined with the number of projects I have on the go at any one time.

I have a ham license - had it for ages, in fact I was a ham in the UK where I grew up.  Here in Michigan, I had a nice rotating Yagi antenna system set up and had a contact in Spain on my ICOM IC7000 before a 70 mph wind storm took it all down. Now, the mangled parts are sitting under my deck and the XYL won't let me put it back up

[Gandalf_Sr]

@WattsThat
I was looking at your pictures again, specifically the second one and it looks like you're taking 5V logic from a genuine Arduino Uno (I think they are 5V).  It looks like you are feeding the 5V reference voltage into the Vext pin but you need to put the switch in the Vext position to have the Vext be used as Vcca of the voltage level translator.  Technically, you're feeding 5V logic into the 'A' side of the chip and Vcca is running at whatever the onboard Vadj is set to which is 3.9V max in my limited experience.  This doesn't exceed the absolute maximum ratings of the voltage level translator and it clearly works but it's not my recommended best practice.

Here's my 'rules' for working with 5V logic.
1. Set SW1 to the Vext position (Vcca is pulled to ground by a 100k resistor).
2. Connect the device under test's 5V rail to the Vext pin on J1

RTFM (read the friendly manual) 

[NoisyBoy]

For anyone who has not placed order for the components in the shopping cart yet, a few of them are on backorder at DigiKey.  I placed the order last week, and I am having them ship them all at once, the ship date is May 27th.  I am not in a hurry and didn't want to check Mouser to recreate the cart, but for those of you who can't wait to start building, you may want to shop alternate sources.

BTW, the boards look great, thanks to Gandalf_Sr for putting them together 

[Gandalf_Sr]

For anyone who has not placed order for the components in the shopping cart yet, a few of them are on backorder at DigiKey.  I placed the order last week, and I am having them ship them all at once, the ship date is May 27th.  I am not in hurry and didn't want to check Mouser to recreate the cart, but for those of you who can't wait to start building, you may want to shop alternate sources.

BTW, the boards look great, thanks to Gandalf_Sr for putting them together 

@NoisyBoy

Thanks for the kind words.

I have components to build about 3 SETS so, if anyone is REALLY stuck for parts, PM me and I might be able to help.

[electricMN]

Has anyone I sent the PCBs out to built their LA probe set yet?  Pictures please!

Haven't started yet. Been sick for the past couple of weeks. Not coronavirus, thankfully. BP issues which seem to be resolved now. Finally getting some spunk back so will probably tackle those boards this week. I'm finishing up building a 40m ham radio.

@electricMN
Sorry to hear you've been sick, hope you feel well now.  These are strange times when we're all stuck at home with SO many things to tinker with.  As I move towards retirement, it occurs to me that I need to be more disciplined with the number of projects I have on the go at any one time.

I have a ham license - had it for ages, in fact I was a ham in the UK where I grew up.  Here in Michigan, I had a nice rotating Yagi antenna system set up and had a contact in Spain on my ICOM IC7000 before a 70 mph wind storm took it all down. Now, the mangled parts are sitting under my deck and the XYL won't let me put it back up

The ham radio I'm building is CW only so I've added another project to my long list. Learn Morse code. 

[Gandalf_Sr]

The ham radio I'm building is CW only so I've added another project to my long list. Learn Morse code. 

Morse can be done on a computer, I once got to 9 wpm mandraulic but it's a masochist's errand these days.

[electricMN]

The ham radio I'm building is CW only so I've added another project to my long list. Learn Morse code. 

Morse can be done on a computer, I once got to 9 wpm mandraulic but it's a masochist's errand these days.

Yup, that's probably the way I'll go. 

[Gandalf_Sr]

So a few of you have asked me to send PCBs overseas from USA to EU or Oz and, to make it affordable, I came up with the solution of putting the PCBs in a medium photo-mailer envelope (weight under 3.5 oz) and marking the customs declaration "Free PCB sample, no commercial value". I did that because the cost of shipping a small insured box with tracking is about $36.

But now I'm looking for feedback; have these packages arrived OK? Please let me know.

[Gandalf_Sr]

So 13 people have now been sent my LA PCBs but we've only seen one set of pictures (other than mine) 

I had one person comment that he had issues soldering the ICs and I wanted to add this tip...

You will get much better results using a no-clean flux pen (they are about $9 each and look like marker pens but they will last a long time - over a year in my case) and the video on You Tube (below) gives a good overview of my approach (it's not my video, I just stumbled across it).  That guy clearly has better eyesight than me, I work under a stereo microscope, and although the flux will dry up if left for a while, I don't fully support the absolute urgency he suggests to get the solder to the pins before the flux has evaporated. I clean the area to be worked on with acetone before I start and then swipe the flux pen over the pins I want to solder before soldering.  Don't worry if the solder bridges several pins, use the wick/braid to get it off afterwards - tip, swipe the flux pen over the part of the braid you're about to use before using it to wick away the excess solder.  I can get good results on 0.5 mm pitch ICs using this method.

[Gandalf_Sr]

I once had several dozen sheets of various 3 cent stamps from the 1930's.  They could be bought for 10% less than face value (they had no collector value) and were quite beautiful with engraved printing.   I used them when postal rates went up 3 cents and had a lot left over.   They made for a very impressive envelope when used for the full letter rate.

Now I'm thinking of the awesome Cohen Bros movie 'Fargo; in one part, Norm who was Marge the pregnant policewoman's husband, sat at home painting a picture of a mallard that he entered into a competition and it ended up on the 3 cent stamp. Norm complained that nobody uses 3 cent stamps.   

[martinr33]

For soldering those ICs - drag soldering works almost impossibly well. The key is, liquid flux. Use a water wash type, no clean if  you can find it. If you have decent soldering skills already, it is easy to get good enough quickly, meaning a bit of excess solder on the last few pins that you have to remove.

So - imagine you have a SMT SOIC with nasty, blobby solder joints and runs between the pins...

1) Paint the pins with flux, liberally.
2) Put your soldering iron tip on the end of the row. There will be some spitting and sizzling, as it slows the solder will melt.
3) Drag your iron gently and slowly across the pins. The solder will blob up and follow the iron, leaving perfect bright shiny joints behind.
4) You may have to pull excess solder off of the last few pins with wick or a solder puller.
5) If you like - do it again to get everything clean.
6) Clean your board when done.

For 0603s - I put a dot of solder on one pad, then hold the 0603 on it with tweezers, then melt the solder (liquid flux again). Then, I can solder the other end.


Did I mention LIQUID FLUX enough? water wash, not rosin. 
 

[NoisyBoy]

My order from DigiKey likely won’t arrive until end of the month.  But for soldering SMTs, Dave’s video is excellent for newbies, https://youtu.be/b9FC9fAlfQE, it allows you to see martinr33’s recommendations in action.

This is the no clean flux pen I use, refillable for those of us who prefer green products.  Works well for SMT soldering.

SRA #312 Soldering Flux Pen Low-Solids, No-Clean 10ml - Refillable https://www.amazon.com/dp/B008OC0E5M/ref=cm_sw_r_cp_tai_RnHREbW2DH3R4

[Bog1]

I really like what you've done here! Would you be willing to attach the layout so I can order a set of PCBs from JLC?
I'm based in Germany if you want to rather sell them yourself

[Gandalf_Sr]

I'd rather not, I imagine that the design would quickly appear on Aliexpress if I posted the Gerbers. I still have spare PCBs, if you want some PM me.

[NoisyBoy]

For those who hasn't bought the components from DigiKeys yet, I just got an update today that the ship date for the complete order has been further delayed to 6/17 (I placed the order two weeks ago).  So please plan accordingly.

[0xde4dbeef]

Hey what a nice project! I'm new here, just got a MSO5000 and found this.
I'd love to build one too, however shipping from China to the US back to Europe seems a bit excessive. What if you'd pick one reputable eev-member from europe (guess that's not me then) who gets another batch and ships them to the EU area? Would shorten the shipping around the world. Just as a suggestion. I'm going to order on JLC soon too, I would not mind to some additional pcbs in that order. But I respect your reasoning, it makes sense I guess.

[Gandalf_Sr]

I'm really not trying to run this as a business, I have sold just 12 sets of PCBs so far world-wide.

I've PMd you with info on how I can send you a SET cheaply but there's no insurance or tracking.

[Gandalf_Sr]

I've sent out 13 sets of PCBs, mostly USA via USPS Priority Mail which is specified at 2 or 3 day and is insured but getting money back from USPS will be like getting blood from a stone I fear.

I've just raised one complaint to USPS for a package sent to Georgia USA on 4/22 that hasn't arrived.

Nobody seems to have received the packages I sent to Europe but USPS web site says 7-21 days for delivery so there's still time.

Apologies to all but I'm trying my best and we have to make some allowances for the postal workers whose lives probably suck more than ours right now.

What a fustercluck!

[NoisyBoy]

Yes, I think USPS is running a little behind now.  The two sets of PCB got to me one or two days behind the scheduled delivery date.

The shipping delay is out of your control, you did all of us a great favor by putting the design together, so don't be too hard on yourself, we are all grateful for your work.  Thank you.

[tv84]

Exactly!

I deeply appreciate all your effort. I haven't received it and, believe me, that I received something from China yesterday that was ordered after your shipping date... 

Maybe Trump blocked US exportations...

[Gandalf_Sr]

Thanks, you guys pulled me back from the ledge there! I was ready to jump.

[TK]

Is it possible to set the threshold from the scope or you are limited to 3.3V and 5V logic only?  Does it work with ECL (-1.3V)?

[Gandalf_Sr]

The threshold settings on the scope make no difference, the voltage level translation IC sets the threshold level depending on the voltage at VccA which is set either by the Vadj pot or the Vext voltage depending on which way the switch is thrown.

My understanding of ECL is that all the voltages are negative so it won't work; unless maybe you can connect it up backwards and set Vadj at around 2V then you'd have to reverse the logic as a low would be +1.75 volts and high would be +0.9V? It might work.

[TK]

What happens when you set the threshold in the scope that is different to 3.3V and 5V?  for example if you use the 3.3V board and then set the threshold to a different setting, does it still capture the signals correctly?  Or they need to match (board and scope setting)?

[Gandalf_Sr]

What happens when you set the threshold in the scope that is different to 3.3V and 5V?  for example if you use the 3.3V board and then set the threshold to a different setting, does it still capture the signals correctly?  Or they need to match (board and scope setting)?

The threshold settings in the scope don't do anything and can be ignored (they do provide a variable voltage to the front connector but my circuit does nothing with it).

The datasheets for the SN74AXC8T245 voltage level translator (VLT) has the table below to give the threshold voltages and, as you can see, it's purely a function of VccA (VccB is running at 3.3V all the time).  The DS90LV047A driver ICs take the 3.3V logic levels from the B side of the VLT and send them as differential LVDS signals to the scope.  If you built with SN74LVS8T245 VLT ICs (the 5V version) then you'll have to look up the equivalent table in the datasheet.

[Gandalf_Sr]

Sorry, that table was for the output levels, the table below is the one for the input levels.

[Gandalf_Sr]

Is it possible to set the threshold from the scope or you are limited to 3.3V and 5V logic only?  Does it work with ECL (-1.3V)?

Go back and read the first post; it explains that you can deal with positive going logic where the +ve rail is between 1.65 and 5.5V and there is a choice between 2 different voltage level translators which cover voltage ranges as follows.

1. 0.65V - 3.6V logic levels using a SN74AXC8T245 as U3 on the probe PCB
2. 1.6V - 5.5V logic levels using a SN74LVC8T245 as U3 on the probe PCB (and other minor component differences)

The definition of high and low on the inputs is purely a function of the voltage on VccA of the VLT IC, the setting on the scope can be ignored.

[S. Petrukhin]

Hi, friends!

I'm create new topic with EasyEDA project low cost logic analyzer probe for Rigol MSO5000 here:
https://www.eevblog.com/forum/testgear/low-cost-logic-analyzer-probe-for-rigol-mso5000-easyeda-project/

[knapik]

Woah, I finallly got my boards in the mailbox today . Thanks Santa

[Gandalf_Sr]

Woah, I finallly got my boards in the mailbox today . Thanks Santa

Wow! I posted them to you on April 15th

[ve2mrx]

Hi everyone!

I'm an absolute newbie at SMT but have plenty of experience with PTH, how would you rate the difficulty of assembly, any "must haves"?

So far, it needs an appropriate soldering iron and "no clean" flux. Anything else? Microscope?

It would be a nice addition to my MSO5074, if I manage to assemble it...

73,
Martin

[Gandalf_Sr]

I do all my work under a microscope but my eyes are old and worn out.  A good pair of tweezers is essential but forget about plastic ones, they melt. The design is deliberately 0603 and ICs with legs to make it hand buildable, U8 is the smallest pitch so I would put that down first.

Believe it or not, I use a fairly large T12 'K' soldering iron tip that looks like a small modelling knife; you can use the sharp end to get to tiny points or flip it around and use the flat edge for soldering wick.  I like it because it has great thermal flow.

[NoisyBoy]

Hey everyone, I am busy with home schooling and don't have time to write much.  But my order from DigiKey showed up a few weeks early, due to kids responsibilities, it took me a week before I could work on it, I built one scope connector board, and 4 (2 x 5V, and 2 x 3.3V) input boards. 

I will provide a writeup when I have more time this weekend to capture lessons learned as a supplement to the excellent material Gandalf_Sr has provided.
I hope it will be helpful those who are about to begin the build shortly.

As far as skill required, 0603 size components is not something you would want to solder without magnification devices, so it is definitely more care required than through hole.  I will share the tools I used in my writeup later.    I don't do 0603 on a regular basis either, at the end, I destroyed two LEDs, both due to reversed polarity, mistake on my part. 

Stay tuned.

[knapik]

Wow! I posted them to you on April 15th

Everything has been delayed horribly due to virus reasons. I'm thankful that they came at all.

[Gandalf_Sr]

Wow! I posted them to you on April 15th

Everything has been delayed horribly due to virus reasons. I'm thankful that they came at all.

Me too, I don't really care about money which I would happily refund it's just frustrating to go to all the trouble of packing up PCBs and paying $8, $10, $14 to ship them and find that, more than a month later, many haven't arrived.

[skip]

It works!  I discovered this thread last Tueday and today I have my very own working probe set.  I ordered the boards from Ted on Tuesday and they arrived on Thursday, I ordered the parts from Digikey on Wednesday and they arrived on Friday!  Wow, what amazing service.

So far I've built 2 X 3.3v versions, I think I'll take a break and build 5 volt version if and when I actually need them.

I must say the assembly was a WORKOUT for me, I mostly do software work and although I've been soldering for over 50 years stuff this tiny was a real challenge!

Thank god for my Metcal (ebay) soldering iron and my Amscope microscope or it would have been hopeless.  I was too paranoid to try drag soldering so I soldered each pin individually with my .25mm tip.  I'll might try drag soldering on the next board, the resistors and caps took most of the time anyway.

All thee boards worked perfectly the first time.

The picture shows my completed probe wired to a surplus Pano Logic thin client which I've programmed with an 8 bit counter clocked by 125 Mhz to generate test signals.  As you can see the scope measured and displayed the fastest signal of 62.5 Mhz without problem.

Thanks for the project Ted!

[notfaded1]

Can't beat Metcal after I bought a 5k with dual irons... I'll never go back.

[Gandalf_Sr]

Nice job Skip, glad they are working for you.

[electricMN]

I finally got some boards built and tested. The only problem I found building them was locating a 1.4mm key wrench to fit the potentiometer. I ended up getting a couple from McMaster-Carr, I was ordering some other stuff from them anyway.

I tested it by hooking it up to an Arduino Uno board which had a digital caliper hooked to it reading the serial data from the caliper. I ran into a problem with hooking the Arduino I/O pins to the LA. The Arduino has built in pull-up resistors on the inputs that are 20K. The LA has 10K pull-down resistors on its inputs. I had to add 2K pull up resistors on the I/O pins on the Arduino in order to get it to work with the LA. I think I'm going to replace the pull-down resistors on the LA with much larger values. I think they're there just so there are no floating inputs on unused inputs.

Thanks for the hard work putting this project together Ted. 

[Gandalf_Sr]

electricMN

Thanks for posting the pictures and the comment about the pull down resistors. I discuss these resistors earlier in the thread; I found it works fine without them but the datasheet for the voltage level translator IC says the input pins shouldn't be left floating - I'm sure that 100k or even 1 Meg would work just fine.

The Piher trim pot was chosen because it's sealed and rated for 1,000 operations (unlike many trimmers that are only rated for 100). If you check the datasheet, you'll see that it's supposed to be available in Phillips head type too but the only type Digikey ever seems to have in stock is the Hex drive.

Anyway, glad that you got it working OK and the pictures look great!

 

[NoisyBoy]

Gandalr_Sr,

Just used your model for the 3D case printing, it worked perfectly.  I use the case to color code the boards, orange (caution) for the 3.3V, and green for the 5V. 

Thanks again for all the hard work you put into the probes.

[Gandalf_Sr]

Noisy_Boy,

They look great   Thanks for posting the pictures.

[tv84]

Gandalf_Sr, I almost cried... 

[Gandalf_Sr]

Ho Lee Fook!  I sent that package to you on April 15th, that's 4 days short of 4 months!

Happy that it actually arrived though.

[0xde4dbeef]

Ho Lee Fook!  I sent that package to you on April 15th, that's 4 days short of 4 months!

Happy that it actually arrived though.

Dang, that means there's still hope for mine to arrive! Seems they should be here in about 3 weeks then   

[Gandalf_Sr]

Sorry man 

Although it was posted at the height of the Covid 19 pandemic plus the USPS is struggling under bad 'leadership'.

[0xde4dbeef]

Not your fault mate! Apparently it's significantly faster to get stuff from china to europe than from the US, but let's not get political in here.
Got the parts ready and look forward to getting the boards and build them, I'm not in a rush. Would've gotten the original ones then 

[Gandalf_Sr]

Not your fault mate! Apparently it's significantly faster to get stuff from china to europe than from the US, but let's not get political in here.
Got the parts ready and look forward to getting the boards and build them, I'm not in a rush. Would've gotten the original ones then 

Thanks but if it doesn't arrive soon(ish) let's discuss sending you another set.

[0xde4dbeef]

So they arrived today! 
By the day 4 months!  But they are here! Now going to find out if I managed to order all and the correct parts 

[tv84]

So they arrived today! 

  I was not last!!!

[Gandalf_Sr]

I just posted a SET to France, I wonder how long that will take?  International shipping has become a joke these days.

[Gandalf_Sr]

A member has contacted me about a SET of boards that he wants to adapt to an MSO1000Z like an RPL116.  I went back and looked at this thread but it's not clear to me whether the output of my chips will drive into an MSO1000Z, will it?  Do I need terminating resistors?

He's talking about using a ribbon cable to adapt from my setup but the neatest solution would be for me to create a variation of the connector PCB.  Anyone interested in that?

[cstereo]

PCB posted in the US on September 9th and received today in France after only 1 week !

Thank you again for your time.

[Gandalf_Sr]

PCB posted in the US on September 9th and received today in France after only 1 week !

Thank you again for your time.

You are welcome, hope they work out well for you.

[mtnzap73]

I am late to the party, but have a soldering question.
I read all I could find in the threads above re flux, soldering advice.
But, I did not see anything about using solder paste, and an air solder station.
They are not too expensive, and are made for SM obviously.
It even seems that DK's price for an Aoyue 852 is well less than Amazon.
Isn't this a fine justification for another cool tool? Just slip it into the DK order ...

[mtnzap73]

Well that was not a popular question. After a bunch of research I can see why. I took some advice I read in this forum to stick with single function solder tools. I have learned that lesson for other things so it is good that I realized it again.

I am about to do the DK order. Based on the experience of others, are there any specific parts in the BoM that perhaps should be increased in quantity to serve as spares for soldering errors, etc.?

Thanks.

[knapik]

I am late to the party, but have a soldering question.
I read all I could find in the threads above re flux, soldering advice.
But, I did not see anything about using solder paste, and an air solder station.
They are not too expensive, and are made for SM obviously.
It even seems that DK's price for an Aoyue 852 is well less than Amazon.
Isn't this a fine justification for another cool tool? Just slip it into the DK order ...

I hand soldered mine, but made a couple of mistakes where I had to bring out a hot air station to fix. If you ever plan to do more SMD repairs, a hot air station is a good idea. No comments on that specific hot air station though.

[Gandalf_Sr]

I own a hot air rework but I see it as a tool to take multi-legged parts off a PCB, not put them on. I use a T12 K tip to solder pins individually under a microscope and then solder wick to remove excess solder.

To put down my parts, I no-clean flux the pads and then use thin solder to put solder onto 1 pad, choose one that is connected to a track not one that is unconnected, and avoid a ground pin as you'll need more heat/time.  Then I carefully position the IC with tweezers under the microscope - the plan view should be correct, the IC will be sitting high with the pin resting on the soldered pad - and heat that one pre-soldered pad until the IC drops down to sit flush with the PCB - use the lightest touch possible with the tweezers, forcing the IC around will risk pulling the pad off the PCB. Once I'm happy with the IC position, I go in and solder one pad on the opposite side; again make sure the IC is aligned. Now, go back and solder the remaining pads.  If there are bridged pins or too much solder, I take a piece of thin solder wick which I pre-wet with no-clean flux to creep up un 3 or 4 pads at once, what happens is that the wick gets a load of solder in it and it then acts as a reservoir to add/subtract solder from multiple pins at once.

This approach has been very successful for ICs with pitches down to 0.5 mm and 0603 size discretes.  My design deliberately does not go lower than these sizes to make it hand-buildable.

[mtnzap73]

I received my boards recently!
Now for the easy part.

Thanks again Gandalf_Sr.

[Gandalf_Sr]

I received my boards recently!
Now for the easy part.

Thanks again Gandalf_Sr.

You're welcome mtnzap, post some pictures when you get them done.

[S. Petrukhin]

I use a T12 K tip to solder pins individually under a microscope and then solder wick to remove excess solder.

I use T12 KU tip for 0603 and 0.5mm pitch - if you wipe off the solder on a wet sponge, it will drink all the jumpers, I have never to use solder wick while soldering. Just an extra drop of fresh flux.

I bought BCM2 a long time ago, but I haven't tried it yet. Just tomorrow I will try to solder them chips 0.5 mm pitch.
If it doesn't work out, good old KU will fix it. 

[fjalvingh]

@gandalf_sr Very late to the party but- would it be possible to get those boards still?

[Gandalf_Sr]

@gandalf_sr Very late to the party but- would it be possible to get those boards still?

Yes, I still have some boards left. PM me.

[Gandalf_Sr]

Here in Washtenaw County, Michigan, USA, the Covid 19 virus is running rampant; we know 3 people who have (or have had) it, and Michigan has just gone into strict lockdown again with all bars and restaurants closed.

I've had a couple of requests recently for PCBs from non US people.  I have sent overseas before but, for now, I need to restrict to US mailings only because, to send overseas, I have to stand in line at the Post Office and fill in a customs form which I am unwilling to do for obvious reasons.

I will still ship to the USA because, when shipping to the US, I can print shipping and put in my mailbox for outgoing collection (as long as my shipping supplies last).

Thanks for your understanding.

[S. Petrukhin]

Friends, who really need a probe for a logic analyzer, you can use my simplified version - it is very cheap and affordable, you can order boards for $2 on JLCBCB and components for $18 on LCSC.

Sir Gandalf_Sr made a very important and decisive contribution to the development of this option, and this is also his work.

[texaspyro]

because, to send overseas, I have to stand in line at the Post Office and fill in a customs form which I am unwilling to do for obvious reasons.

You can do customs forms online...  you would still need to mail stuff overses online.

[Gandalf_Sr]

because, to send overseas, I have to stand in line at the Post Office and fill in a customs form which I am unwilling to do for obvious reasons.

You can do customs forms online...  you would still need to mail stuff overses online.

In theory yes; but when I've tried to do this through the USPS web forms (yes I have an account), it ends up failing and telling me I have to appear in person at a PO.

[MiniEE]

Hey. I would be intrested in set or two as well. However im also in Europe. I was wondering that you said you don't do this for profit. And you made schematic available as well. Wouldn't you mind share with us Gerber files? Then we could order them ourselves from china… which would be a lot faster and less hassle for you. I hope my question wasn't offensive…

[Gandalf_Sr]

Hey. I would be intrested in set or two as well. However im also in Europe. I was wondering that you said you don't do this for profit. And you made schematic available as well. Wouldn't you mind share with us Gerber files? Then we could order them ourselves from china… which would be a lot faster and less hassle for you. I hope my question wasn't offensive…

Sorry, I've been asked this before and the answer is no.

[MiniEE]

Hey. I would be intrested in set or two as well. However im also in Europe. I was wondering that you said you don't do this for profit. And you made schematic available as well. Wouldn't you mind share with us Gerber files? Then we could order them ourselves from china… which would be a lot faster and less hassle for you. I hope my question wasn't offensive…

Sorry, I've been asked this before and the answer is no.

No worries. It's understundable.

[ddffnn]

TI has a new level shifter SN74LXC8T245-Q1 that can run from 1.1 to 5.5 V. This might be a good replacement for SN74LVC8T245 on the 5V version.

[Gandalf_Sr]

ddffnn
Great find on the SN74LXC8T245, thanks!  FYI, there is only one version of the probe bare PCB, it's made into a 3.3V or 5.0 volt variant by which voltage level translator you put in for U3 (with a few other slight component changes).

I have done a cross-check and it does look like we can fit a SN74LXC8T245 for U3 on the Probe PCB with R10 changed to 0 and then the PCB can run between 1.1V and 3.9V using the onboard Vadj LDO supply or you can feed an external 5V in (Abs max is 6.5V) to run the logic at 5V levels. With this change you lose the ability to go as low as 0.65V logic levels and, to get over 3.9V, you will have to supply an external VccA because you can only supply VccA with up to 3.9V Vadj from the Probe PCB. The SN74LXC8T245 datasheet also says it will support up to 420-Mbps for 3.3 V to 5.0 V

I will buy/sample a couple of the SN74LXC8T245 ICs and try them out.

[fozzyvis]

Looking at the schematics, trying to learn.
Please correct me if I'm wrong. Am I correct to think that the purpose of this set is to:

• Decouple/buffer (not sure of the correct term here, but those two should convey the idea-hopefully?) the inputs (the 200R resistor)
• Slightly load the inputs so that their levels aren't floating (the 10k resistors)
• Shift The inputs levels to a specific voltage (using the SN74AXC8T245)
• Convert the single-ended inputs to a differential (LVDS) signal (DS90LV047A), which is what the scope inputs expect

And the main difficulty is that this is a rather high-speed "product" so length matching and impedance of the power sources becomes critical?

Right?

I am just clueless about the note "Vref is connected to GND at remote end" (on the connector towards the scope). Why is the Vref connected to ground? Why on the remote end and not locally?

[Gandalf_Sr]

Looking at the schematics, trying to learn.
Please correct me if I'm wrong. Am I correct to think that the purpose of this set is to:

• Decouple/buffer (not sure of the correct term here, but those two should convey the idea-hopefully?) the inputs (the 200R resistor)
• Slightly load the inputs so that their levels aren't floating (the 10k resistors)
• Shift The inputs levels to a specific voltage (using the SN74AXC8T245)
• Convert the single-ended inputs to a differential (LVDS) signal (DS90LV047A), which is what the scope inputs expect

And the main difficulty is that this is a rather high-speed "product" so length matching and impedance of the power sources becomes critical?

Right?

I am just clueless about the note "Vref is connected to GND at remote end" (on the connector towards the scope). Why is the Vref connected to ground? Why on the remote end and not locally?

1. There are 200 Ohm resistors in series as it's good practice to consider what happens if an over current or over voltage situation occurs
2. Yes, the 10k resistors are there to provide a load on the inputs.  The level translator datasheet says that the inputs should not be left floating but I find it works just fine with no 10k load resistors
3. Yes, on the probe PCB, one of the key functions is to perform voltage level translation
4. Yes, the scope needs to see LVDS differential signals

Other comments.
- Trace length matching isn't super critical at 200 MHz but I have matched within a few mm for differential pairs.  I have tested at 200 MHz clock rate and it works.
- Vref is a ground that has a confusing label. I originally fed Vref from the scope, through the connector PCB, through the ribbon cable, and to the header on the probe PCB but then didn't use it so I made it an extra ground feed from the connector PCB; I'm just pointing out that the pin marked Vref is really a ground connection.  The Vref that comes from the scope is the one that is supposed to set the logic level but it doesn't do anything, the voltage level translators take care of that based on the VccA voltage, it's detailed in the datasheets but you don't need to worry about it, just set the VccA for the system you're probing.

[S. Petrukhin]

The Vref that comes from the scope is the one that is supposed to set the logic level but it doesn't do anything, the voltage level translators take care of that based on the VccA voltage, it's detailed in the datasheets but you don't need to worry about it, just set the VccA for the system you're probing.

Hi, Gandalf_Sr!

I checked both Vref outputs from the scope - it sets voltage to these outputs, which user selects in LA menu.
In groups for 1-8 and 9-16 LA inputs.

[Gandalf_Sr]

The Vref that comes from the scope is the one that is supposed to set the logic level but it doesn't do anything, the voltage level translators take care of that based on the VccA voltage, it's detailed in the datasheets but you don't need to worry about it, just set the VccA for the system you're probing.

Hi, Gandalf_Sr!

I checked both Vref outputs from the scope - it sets voltage to these outputs, which user selects in LA menu.
In groups for 1-8 and 9-16 LA inputs.

I know but, in my design, the Vref output from the scope is not connected to anything.  The LVDS ICs run from 3.3V and that gives the voltage that the MSO5000 expects.  The voltage level translator ICs automatically adjust the Hi Lo threshold voltage based on the value supplied to VccA,

[S. Petrukhin]

The Vref that comes from the scope is the one that is supposed to set the logic level but it doesn't do anything, the voltage level translators take care of that based on the VccA voltage, it's detailed in the datasheets but you don't need to worry about it, just set the VccA for the system you're probing.

Hi, Gandalf_Sr!

I checked both Vref outputs from the scope - it sets voltage to these outputs, which user selects in LA menu.
In groups for 1-8 and 9-16 LA inputs.

I know but, in my design, the Vref output from the scope is not connected to anything.  The LVDS ICs run from 3.3V and that gives the voltage that the MSO5000 expects.  The voltage level translator ICs automatically adjust the Hi Lo threshold voltage based on the value supplied to VccA,

I reminded you just in case I didn't notice...
I generally find this feature strange or rarely used. If you need some special non-digital signals to explore LA, RS-232 for example, - there are 4 analog inputs. 

[2efa4605b83bf1af48bf6736b]

I received my boards this week and put them together last night. To my surprise (due to my soldering skills), it worked! The 0603 components and fine ICs tested me out so I bought a magnifying lamp which was well worth it. Here are a few photos. I found that Vadj did not correspond with the build notes but otherwise it was all good. Thanks very much to Gandalf Sr. for his work on this.

[S. Petrukhin]

I received my boards this week and put them together last night. To my surprise (due to my soldering skills), it worked! The 0603 components and fine ICs tested me out so I bought a magnifying lamp which was well worth it. Here are a few photos. I found that Vadj did not correspond with the build notes but otherwise it was all good. Thanks very much to Gandalf Sr. for his work on this.

I recommend that you use flux when soldering to avoid sharp solder tails. 

[Gandalf_Sr]

@2efa4605b83bf1af48bf6736b

Thanks for the pictures; I LOL'd when I saw the serial decode 

Vadj is ultimately limited by the supply from the scope (nominally 4.2V) which also passes through the ferrite bead/PTC that's on the connector PCB.  If you used a PTC, that's most likely where you're losing the voltage, I prefer fitting a ferrite bead instead of the PTC.  I chose the adjustable LDO regulator on the probe PCBs because it has the lowest drop out voltage (difference between input and output voltage) I could find, that's why it's relatively expensive.

In the end, the simplest solution to the limitation of the Vadj range is to supply VccA from the circuit under test, the current pulled from the DUT will be microamps.

Anyway, I'm happy that it's working for you.

PS, I noticed that you have 2 missing pins on the 0.1" header on your probe PCB, why was that?

[Zephyrot]

Hey. I would be intrested in set or two as well. However im also in Europe. I was wondering that you said you don't do this for profit. And you made schematic available as well. Wouldn't you mind share with us Gerber files? Then we could order them ourselves from china… which would be a lot faster and less hassle for you. I hope my question wasn't offensive…

Sorry, I've been asked this before and the answer is no.

Hi @Gandalf_Sr,

first of all thx for doing all this work. It looks fantastic.

I can understand that you do not want to share the Gerber files and are currently unable to send PCBs all over the world.

But maybe this is a solution: On https://www.pcbway.com/project/shareproject/ you can share your PCBs without allowing others to download it. Everyone can order them still. There are probably other PCB manufacturers that offer such a service too.

[whatisthis]

Has anyone used any computer programs to work with the logic analyzer?

I tried PulseView with this patch, but it is terribly awkward and buggy.

Maybe there are some other simple ways, for example, download the raw data from scope through the SCPI and convert it to the format of the logic analyzer dump viewers?

[S. Petrukhin]

Has anyone used any computer programs to work with the logic analyzer?

This topic is about something else.
But, if you want to explore a known protocol such as SPI, take any BluePill and write/transmit to the PC from SPI to UART dump.

[whatisthis]

This topic is about something else.

Ok, sorry for the offtopic. It seemed to me that this is the most appropriate forum topic for a logic analyzer in mso5000 series, because all interested users have gathered here.

[Gandalf_Sr]

I don't mind you asking the question on my thread.  FWIW, I think that you need 3 tools to look at signal protocols:

1. A scope to look at signal integrity (perhaps triggered off specific bytes/commands)
2. A logic analyzer such as the Salae Logic series that can read and decode massive quantities of data
3. Something like a Bus Pirate which is clunky to use but valuable because you can write to a bus/device with it.

I have all 3

[clytle374]

Just got my 5 boards, they look great.  Finally got a couple days off to get parts ordered, anyway the following were out of stock
ALT U3 was out of stock, able to find in alternate packaging.
D1 out of stock, replaced with thicker LED https://www.digikey.com/en/products/detail/LTST-C190KGKT/160-1435-1-ND/386814?itemSeq=357480811
C1 was out of stock, replaced with  https://www.digikey.com/en/products/detail/C0805C475K8PACTU/399-3133-1-ND/551638?itemSeq=357482706
Hopefully I didn't make a mistake there anywhere.  Be a few weeks as I have other things on the bench and apart needing their turn on the bench. 
Thanks
Cory

[Grippy]

Thank you for the boards, built one 3.3V and it works great! (despite me less than ideal tools since I just moved)  I'm not a monster I cleaned them after taking the pics.

I also found ALT U3 was out of stock for the 5V Version.

TI does have SN74LXC8T245s available so I ordered some of those.

Any component differences expected or can we fit the rest as if it was a 5V version?

PS: No idea why it decided to rotate my images.

[Deckardsvr]

just finished the boards, it's working great ! Thank you Gandalf_Sr 
I had to order the parts from Mouser, it's easier than DK for me; just had to change the 50pin Header Ref. which they didn't have : replacement 3M 6850-4500PL, it fits nicely.
Someone mentioned that the USB Port could be used as a VExt. source, thanks for the tip

[normi]

Hi @Gandalf_Sr

The specification for the LA in the manual appear to be those of the active probe. Do you have details of the specification of the port on the MSO5000. Like max voltage.

[Gandalf_Sr]

Hi @Gandalf_Sr

The specification for the LA in the manual appear to be those of the active probe. Do you have details of the specification of the port on the MSO5000. Like max voltage.

Sorry this has been a long time in replying.  Clearly the MSO5000 official probe can take much higher logic voltages than 5V but my probes are limited by the minimum and maximum voltages which are dictated by the min/mac Vcc for whatever voltage level translator IC you use for U3.  Basically you can go up to 6.5V logic depending on what U3 is fitted.

[lastguy]

Very nice! are these kit still available? if possible I want PCB and connectors. I might need to go back find how to order.
You used to mention to check whether 100M data works or try new chips, any update?
Another question, if scope set 3.3V logic, what is Vref output level? I know your design doesn't use Vref yet I still like to know thanks.

[Gandalf_Sr]

Sorry it's been so long with no posts - my eldest son died (aged 41) in Nov 2021 and I'm just getting back to something like normal. I do still have PCBs if anyone wants them but shipping to a non-US address is a pain.

However, I'm making a trip to London UK / EU leaving on Jul 27th so, if you want some PCBs, let me know and I should be able to post them in the UK/EU.

One thing I will say is that the chips are in crazy short supply and I do not have any spares.

[fjalvingh]

Oh Gandalf_sr, that is really terrible and sad news. I wish you the best in getting over that, and hope that picking up the hobby will help.

[mawyatt]

Dear Gandalf_Sr,

So very sorry about the loss of your son, and know somewhat about the pain of losing one's child. Having lost our oldest son 27 years ago and our youngest son last Aug (39), and our youngest daughter is in a horrible incurable state. A parent should never have to bury a child, and that stretches one's faith!!

If it helps, don't try and keep everything inside, there are others that have similar experiences that can help to talk with. I know, at first I've tried to keep everything inside and talking with others has helped a bit and gave me a better perspective on life in general.

Somehow electronics seems to be a momentary escape from the reality we've been unfairly dealt. Helps calm you down, and hope this can also be of some help for you.
Just "talking" with all the great folks on here with the common thread of electronics is kind of a therapy in itself, I know it's certainly helped and continues to help me get through all the difficulties that life has unfairly thrown our way.

Best wishes and condolences on the loss of your son.

Best,

[Gandalf_Sr]

Thanks for all your kind wishes, I'm OK (I think).

[lmamakos]

I assembled my boards today - 4 pods and the MSO plug-in board.  I built two each for each voltage range, because why not?  It's late, only done a smoke test and the LED's come on, so far so good!   I need to give them a good wash and then take them for a ride on my MSO5074.

The 3.3v LDO was unavailable, and I thought I had some others here already.  Turns out I had the wrong package, but managed to bodge it on there anyway..

[fest]

I considered adapting this design to use Vref from the MSO- providing Vcca with an amplified Vref voltage of gain = 16 should result in Vcca voltages very close to CMOS levels that are available as presets on the scope (e.g. when CMOS 1.8 is selected, Vref voltage is 112mV on my scope, after amplification Vcca would be 1.79V). The threshold levels wouldn't exactly match the indicated voltage on MSO, but appear to be close enough for the CMOS 1.2-5V ranges I'm mostly interested in). Of course, one must also limit the Vcca between 0 and max. level shifter's Vcca.

However, one important aspect to note is that SN74AXC8T245 has a propagation delay that depends on Vcc. With Vcca = 0.8V, Vccb = 3.3V the propagation delay is 0.5-35ns, which would limit it's operation at ~28MHz in the worst case.

SN74LXC8T245 which is advertised as faster than SN74AXC8T245, the LXC version appears to be worse at low voltages: at Vcca=1.2V, Vccb = 3.3V, SN74AXC8T245 has delay of 0.5-7ns, while SN74LXC8T245 has a delay of 5-22ns.

I briefly looked at high speed comparator design, but I didn't like what I saw (Rigol logic probe does not seem expensive anymore), so I'll likely take a stab at such a voltage-adjustable version and hope for the best (either of them seem to be ok for 1.8V at ~100MHz which is my immediate need).

[mtnzap73]

Hi Gandalf_Sr

Long time no message. Like about 3 years. I guess a pandemic has its effects.
I was looking to see if you are still able to send the stencil files.
The LA probe project sat on my shelf until now, and I am getting all ready to start it up again.
I did try PM like we were doing when I purchased the boards ....

Best regards,

Stan
Calgary

[mtnzap73]

With all respect, can I ask the forum the following:
> did anyone get and use the solder stencils?
> is there a way for me to get them?
> am I asking the question correctly?

[mtnzap73]

Hi Imamakos,

Nice to see your success.
I also have the kit and am getting ready to assemble it.

Did you obtain or use solder stencils?

[Gandalf_Sr]

Hey all, the stencils are already here in this thread, page 2

I am now retired and not very active on this thread; sorry for late replies to messages

[lmamakos]

Did you obtain or use solder stencils?

No, I just hand soldered all the boards with thin wire solder.

[LoveTheFactory]

Anyone tried this Logic Analyzer probe with with the new Rigol DHO800/900 line ? 

 @yGandalf_Sr, any boards left ? 

Thank you for sharing with us...

You are a awesome person. I like your style.  You help
us understand how we are supposed to act.

[Nikki Smith]

Anyone tried this Logic Analyzer probe with with the new Rigol DHO800/900 line ? 

I've made a different design that should work with the new DHO900. And I'm hoping to hack my DHO804 so it supports a logic analyser too 
https://climbers.net/sbc/clone-pla2216-logic-probe-analyzer/

[ebastler]

I've made a different design that should work with the new DHO900.

Just to clarify: Your design has various improvements (reduced via count, tidier dimensions, improved parts availability etc.) -- but none of these are required to make it work with the DSO900, right? I.e. the older designs should work as well, since the MSO5000 and DSO900 use identical logic analyzer connections? Thanks!