MS05000 Budget Logic Analyzer Probe Set Design

[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!