LaPOD: Low cost Logic Analyzer probe for MSO5k, DHO900 and more!

[oliv3r]

The wiggles above the voltage dividers are needed, because the center two channels come from the top of the chip, so need to go all the way from the top, to the bottom.

No, I don't think they are needed. They are in channels 0 and 3, right? And now you have created additional wiggles in channels 1 and 2 just above the 2*4 plug. They pretty much even out, so just do away with all four of them -- that's what I meant.

So on the top-size, from the chip to the resistor/capacitor network, there's a wiggle to compensate for the length of channel 1 & 2 which come from the top of the chip, and run on the bottom side. So all traces from the chip, to the network are all 4 in identical length.  The wiggles after the network, is to match the length of the outputs going to the 2x4.

There is one thing that isn't properly matched though, just because I don't know how, and that's the length of the wires in the network, they should be the same but I wouldn't be supprised there's an error inthere, especially in the lm7234 pod, as the network isn't oriented identically, to make things fit better (0&3 and 1&2 are identical though). And since the parts aren't perfect tetris blocks (resistors and capacitor 2012's have different sized pads ... go figure.

One tiny advantage of not putting the PCB underneath the connector btw, is that we can put in the connector a bit lower, allowing the pod to be not as fat. I even thought of doing the same as with the 50pin connector, and use an SMD layout, for a straight throughole part and side-mount it ... should fit?

Does require clipping some sticking out legs though ...

[ebastler]

So on the top-size, from the chip to the resistor/capacitor network, there's a wiggle to compensate for the length of channel 1 & 2 which come from the top of the chip, and run on the bottom side. So all traces from the chip, to the network are all 4 in identical length.  The wiggles after the network, is to match the length of the outputs going to the 2x4.

I think we are still not talking about the same traces. Referring to the attached montage, I was looking at the length-matching wiggles indicated by the two smaller circles. They seem to be for channels 0 and 3. And now you have added the wiggles for channels 1 and 2, indicated by the larger circle. These four seem to be of very similar length -- so can't you simply remove all four of them?

Edit -- some further, unrelated comments:

• I like the lowered position of the 2*4 connector; makes the vertical alignment nice and symmetrical.
• Don't forget to change the channel numbers on the top and bottom silkscreen to 0..3!
• Please correct the top silkscreen to say LMH7324.

[UK]

Finally, guys, I found a solution for vertical 50p headers!

Firstly, such headers are not rare at all, it’s just that most manufacturers do not mark them as elevated or extra tall.
Secondly, there not many have in the lineup version 2x25.

Even Pololu produce such headers already many years but only in 2x20 version.

BUT if you try to search directly PC104 long pin, you can get a ton of them, its Chinese OEM headers which are very widely available on many markets... amazon, ebay and of course most cheap prices on aliexpress. There exact option 2x25, but as a rescue option 2x5 also available (that may be staked in row by 5).

The main interesting part is that its high may be easily raised just by adding a plastic part salved from common pin header (pic from Pololu nicely illustrate that).

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So now we have an all option for vertical 50p and vertical HDMI sockets 

And as for the vertical HDMI sockets looks like Rigol use C2682172 in their DHO scopes, you can cheek it here... but I think C5204145 definitely more robust.

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PS

...is that we can put in the connector a bit lower, allowing the pod to be not as fat.

Extremely like the idea of low-ride 8p socket position! 

[ebastler]

BUT if you try to search directly PC104 long pin, you can get a ton of them, its Chinese OEM headers which are very widely available on many markets... amazon, ebay and of course most cheap prices on aliexpress. There exact option 2x25, but as a rescue option 2x5 also available (that may be staked in row by 5).

Yes, these should work. They don't even need a spacer permanently installed, I think, since there are so many pins to keep them stable. But of course you need some spacer or alignment aid during soldering, to make sure you solder them in at the right height.

These connectors do not have the little tab which ensures you can't plug them in the wrong way. So the PCB will need some clear lettering on the front to show the user which side is up.

EDIT: Or rather, the 3D-printed enclosure will need to provide that lettering. Or one can try and glue a little plastic tab onto the connector which matches the notch on the scope side.

[UK]

These connectors do not have the little tab which ensures you can't plug them in the wrong way.

Yep, it's definitely not a problem and it just could be a part of the shell.

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I've made a try to calculate the best dimensions for 2х2 PCB, which taking into account all shell clearances and possible margins, should have a perfect fit with both of the scopes!
Also, I want to point out that 50p header should have a slight vertical offset.

To be honest, now I'm even more interested in the version for DHO900 since I plan to get this cute little scope during the winter holidays 

[oliv3r]

So on the top-size, from the chip to the resistor/capacitor network, there's a wiggle to compensate for the length of channel 1 & 2 which come from the top of the chip, and run on the bottom side. So all traces from the chip, to the network are all 4 in identical length.  The wiggles after the network, is to match the length of the outputs going to the 2x4.

I think we are still not talking about the same traces. Referring to the attached montage, I was looking at the length-matching wiggles indicated by the two smaller circles. They seem to be for channels 0 and 3. And now you have added the wiggles for channels 1 and 2, indicated by the larger circle. These four seem to be of very similar length -- so can't you simply remove all four of them?

But I think we are

The yellow lines are the same four lines for all four channels, that's why the wiggles exist before the input of the resistors and caps. You could probably do some math, and reduce the bottom wiggles from the top wiggles, I certainly grant you this, but it makes it harder to raid/verify/maintain. Now you have identical wherever they are measurable. Also, making it harder, and some wiggles still remain. Also, those 'ears' on the left/right side ... plenty of space for those anyway :p Also looks a little more symmetrical this way

Edit -- some further, unrelated comments:

• I like the lowered position of the 2*4 connector; makes the vertical alignment nice and symmetrical.
• Don't forget to change the channel numbers on the top and bottom silkscreen to 0..3!
• Please correct the top silkscreen to say LMH7324.

check, check, check

[ebastler]

The yellow lines are the same four lines for all four channels, that's why the wiggles exist before the input of the resistors and caps. You could probably do some math, and reduce the bottom wiggles from the top wiggles, I certainly grant you this, but it makes it harder to raid/verify/maintain. Now you have identical wherever they are measurable. Also, making it harder, and some wiggles still remain. Also, those 'ears' on the left/right side ... plenty of space for those anyway :p Also looks a little more symmetrical this way

Alright, I see. You prefer to match all four traces below the divider components, and then also match all traces between the divider and the LMH7324. It will certainly work; it just results in more wiggles on the board than needed. But maybe that's just an obsessive-compulsive thing for me...

[oliv3r]

These connectors do not have the little tab which ensures you can't plug them in the wrong way.

Yep, it's definitely not a problem and it just could be a part of the shell.

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I've made a try to calculate the best dimensions for 2х2 PCB, which taking into account all shell clearances and possible margins, should have a perfect fit with both of the scopes!
Also, I want to point out that 50p header should have a slight vertical offset.

To be honest, now I'm even more interested in the version for DHO900 since I plan to get this cute little scope during the winter holidays 

While I get the excitement for the vertical ports, ignoring for a moment that I used the wrong part :p, where in the world would we put the actual traces? I think even going full smd (which still requires the same amount of via's just for the holes to reach the other side, or go hybrid (smd HDMI connectors, throughole IDC connector (or vice versa) we still need a ton of via's just to route all those signals. I've also tried two options, one logical (1, 2, 3, 4) and one shortest trace (2, 1, 4, 3), which gives a rats-nest mess. What I did in the end, per your request, ordering the ports, was only possible by enlarging the PCB by half or full cm, which isn't really an option in this case?

I'd route if if I had any hopes, but with these parts, it would require going with the tiniest pitch, and probably forget about doing length-matched traces ...

[oliv3r]

The yellow lines are the same four lines for all four channels, that's why the wiggles exist before the input of the resistors and caps. You could probably do some math, and reduce the bottom wiggles from the top wiggles, I certainly grant you this, but it makes it harder to raid/verify/maintain. Now you have identical wherever they are measurable. Also, making it harder, and some wiggles still remain. Also, those 'ears' on the left/right side ... plenty of space for those anyway :p Also looks a little more symmetrical this way

Alright, I see. You prefer to match all four traces below the divider components, and then also match all traces between the divider and the LMH7324. It will certainly work; it just results in more wiggles on the board than needed. But maybe that's just an obsessive-compulsive thing for me...

Heh, my OCD says the same, but then I compromise, or convince myself, it's nicer, cleaner and more symmetric to have every measurable line matched in length. So you can pick any line on the pcb, and find its length matched trace. It just depends how you look at it I suppose

Trust me, my OCD is itching with the thought, I just have to convince my OCD is better then your OCD

[ebastler]

While I get the excitement for the vertical ports, ignoring for a moment that I used the wrong part :p, where in the world would we put the actual traces? I think even going full smd (which still requires the same amount of via's just for the holes to reach the other side, or go hybrid (smd HDMI connectors, throughole IDC connector (or vice versa) we still need a ton of via's just to route all those signals. I've also tried two options, one logical (1, 2, 3, 4) and one shortest trace (2, 1, 4, 3), which gives a rats-nest mess. What I did in the end, per your request, ordering the ports, was only possible by enlarging the PCB by half or full cm, which isn't really an option in this case?

I'd route if if I had any hopes, but with these parts, it would require going with the tiniest pitch, and probably forget about doing length-matched traces ...

Umm, are you sure you have oriented the 2*25 connector the right way round? Isn't the notch, and also pin 1, facing up in the scope?

If it really needs to be flipped around, that might give you a fighting chance at routing the PCB for a "logical" HDMI connector order. It will still be very tight, no doubt about that. I agree that switching to SMD-style HDMI connectors could help a bit. (The "brick nogging" type from LCSC; they would still have through-hole mounting tabs though, which are good for stability but get in the way on all layers.)

Other degrees of freedom are rotating the HDMI connectors 180°, or moving them laterally a bit closer to the middle and moving the LEDs to the outside instead. Not sure whether either of these would help with the routing. The lateral move should at least give you a better symmetry of the trace lengths for the left vs. right connectors, requiring less overall trace length and wiggling.

EDIT: I looked again at the pinout of the 2*25 connector. It looks like it is mirrored, rather than rotated? Pin 1 should be in the upper right, I believe. -- So D0..D3 and D8..D11 will be on the right-hand side of the connector. I would definitely place their HDMI connectors on the right side too; don't see a usability problem with that.

[UK]

While I get the excitement for the vertical ports, ignoring for a moment that I used the wrong part :p, where in the world would we put the actual traces? I think even going full smd (which still requires the same amount of via's just for the holes to reach the other side, or go hybrid (smd HDMI connectors, throughole IDC connector (or vice versa) we still need a ton of via's just to route all those signals. I've also tried two options, one logical (1, 2, 3, 4) and one shortest trace (2, 1, 4, 3), which gives a rats-nest mess. What I did in the end, per your request, ordering the ports, was only possible by enlarging the PCB by half or full cm, which isn't really an option in this case?

I'd route if if I had any hopes, but with these parts, it would require going with the tiniest pitch, and probably forget about doing length-matched traces ...

So we have another challenge here  ...the way it can be done is to implement all of that as a stack of two PCBs assembled by two rows of pins on their wide sides (in the style of Arduino Nano).

Pros: doubling the space, separating PCB for HDMI sockets and 50p header, and as a result easier component placement and routing... and cons: 3-4mm additional stack height, doubling PCB cost and additional 10 mins for soldering pins during final assembly

Multi board PCB or multi level PCB is a very common practice when a complex PCB should be fitted in a very tight space.

[oliv3r]

While I get the excitement for the vertical ports, ignoring for a moment that I used the wrong part :p, where in the world would we put the actual traces? I think even going full smd (which still requires the same amount of via's just for the holes to reach the other side, or go hybrid (smd HDMI connectors, throughole IDC connector (or vice versa) we still need a ton of via's just to route all those signals. I've also tried two options, one logical (1, 2, 3, 4) and one shortest trace (2, 1, 4, 3), which gives a rats-nest mess. What I did in the end, per your request, ordering the ports, was only possible by enlarging the PCB by half or full cm, which isn't really an option in this case?

I'd route if if I had any hopes, but with these parts, it would require going with the tiniest pitch, and probably forget about doing length-matched traces ...

So we have another challenge here  ...the way it can be done is to implement all of that as a stack of two PCBs assembled by two rows of pins on their wide sides (in the style of Arduino Nano).

Pros: doubling the space, separating PCB for HDMI sockets and 50p header, and as a result easier component placement and routing... and cons: 3-4mm additional stack height, doubling PCB cost and additional 10 mins for soldering pins during final assembly

Multi board PCB or multi level PCB is a very common practice when a complex PCB should be fitted in a very tight space.

"But is it worth it", the mini-hdmi breakout board is already smaller afaik

Also, the IDC connector was also the wrong one, it was the female kind, but that flipping of the pins, is a triviality and won't affect the rats nest much

[oliv3r]

subscribing...

I asked the admin to split of the thread, but no reply yet

[UK]

"But is it worth it", the mini-hdmi breakout board is already smaller afaik

Also, the IDC connector was also the wrong one, it was the female kind, but that flipping of the pins, is a triviality and won't affect the rats nest much

It depends, if you want to have more fun - yes, if just finish this project asap - definitely not 

I've already started working on several mini HDMI board shells.

[Mechatrommer]

subscribing...

I asked the admin to split of the thread, but no reply yet

10 pages is still easy to handle and usually like all other threads, the first few pages are the most usefull one anyway, can ignore the rest. ymmv. cheers.

[ebastler]

10 pages is still easy to handle and usually like all other threads, the first few pages are the most usefull one anyway, can ignore the rest. ymmv. cheers.

Well, in this particular thread the first 6 pages focus on a low-cost probe with limited capabilities (TTL/CMOS level only, fixed threshold). Towards the end of page 6, oliv3r presents his project which supports different flavors of probes -- either using the same low-cost TTL/CMOS driver, or using the proper (but expensive) comparators and 10:1 divider front-ends as used in the original Rigol probe.

That might make the overall thread a bit hard to follow; and for the second part one could argue that the thread title is a bit misleading. Also, it would be nice to get the DHO900 mentioned in the thread title, since that new scope uses the same logic probes as the MSO5000.

[oliv3r]

subscribing...

I asked the admin to split of the thread, but no reply yet

10 pages is still easy to handle and usually like all other threads, the first few pages are the most usefull one anyway, can ignore the rest. ymmv. cheers.

Problem is, that this has absolutly no relation to easyeda anymore and I really just hijacked the thread, which isn't nice :p

[oliv3r]

So I ran into one little bit of an issue, the 497 resistor doesn't seem to exist ... I know that the original drawing is reverseengineered and 'measured'. But then I also don't understand the original/intended design (at all) to see what is a good fit replacement.

So for now, I'm going with 499Ohm, which does exist, which is 'close enough', and also fits in the E96 list, so not unlogical to have been used. Same for the 90k8, which will become a 90k9

[ebastler]

So I ran into one little bit of an issue, the 497 resistor doesn't seem to exist ... I know that the original drawing is reverseengineered and 'measured'. But then I also don't understand the original/intended design (at all) to see what is a good fit replacement.

So for now, I'm going with 499Ohm, which does exist, which is 'close enough', and also fits in the E96 list, so not unlogical to have been used. Same for the 90k8, which will become a 90k9

Sure, neither of these should be highly critical, and especially the 49x Ohm resistor is not.

The 90kx resistor forms a 10:1 voltage divider together with the 10k resistor, so the "perfect" value would be 90k0. But who cares about a 1% error in the divider ratio?

The 49x resistor in series with the 3.3pF capacitor forms a bypass for high frequencies. I.e. they will not be attenuated by 10:1 but much less; presumably to preserve exact timing of the signal edges. But I don't see why you couldn't even be 10% off here without creating a problem. (The capacitor will have at least a few % tolerance anyway, so your RC time constant won't be that well-defined.)

[oliv3r]

Towards the end of page 6, oliv3r presents his project which supports different flavors of probes -- either using the same low-cost TTL/CMOS driver, or using the proper (but expensive) comparators and 10:1 divider front-ends as used in the original Rigol probe.

Well that's also part of the reason I went with quad pods, to lower the cost of the probe, not often you need 16 * expensive parts

the quad vs dual LMH's is a cost/availability/performance/original thing. We'd want to have 1 pod that's next to identical of the original, and LMH7324's that might be cheaper/but maybe hotter? Who knows why rigol did what they did

[UK]

Thanks to @sergk for the measurements of the DHO900's LA slot... can say with confidence that it's absolutely the same as on MSO5000.

Almost finished the shell for the mini-HDMI board, but the PCB will definitely require some edits for adding several slots and holes for the screws.
@oliv3r, did you already order the PCBs?

[rdtsc]

If this is to be believed, Esaler currently has 942pcs of the LMH7324SQX/NOPB for $0.92ea.

[UK]

Here is the finished shell for oliv3r's breakout board, firstly, it was a bit tricky to make HDMI sockets look visually vertical and LEDs visible from any angle... secondly, to make a proper shadow line with a safe 1mm margin to the LA slot inner walls and find a good place to securely fasten the shell to the board. It prints really well, you can check a closeup photo, where it was printed out in matte black PLA with a standard 0.4mm nozzle and 0.16 layer height.

Really hope oliv3r will publish the final version of its board soon and I won’t have to recreate it from scratch.

...but the PCB will definitely require some edits for adding several slots and holes for the screws.

@oliv3r pls, check the board outline in the attachment. PCB requires small edits.

[ebastler]

Wow, that looks very cool indeed! Very nice job!

I'm curious: What software are you using to design and to produce those stunning renderings? (Which even include the layer structure of the 3D printer apparently, so the software seems to know about the slicing too?)

[Tarloth]

I asked the admin to split of the thread, but no reply yet

Oliver, UK and eblaster !!!!
​
You took a thread from this forum that had nothing to do with your discussion and invaded it with impunity even though eblaster warned about it several times. YOUR DESIGN AND DISCUSSIONS correspond to another thread about to mimic the original POD with a faster LVDS comparator, here in this thread ANOTHER different design was being discussed, simpler, limited but cheaper in which your ideas and designs DO NOT apply. On top of that, you introduces a lot of confusion in this thread and it is no longer even easy to follow the versions when you filled the last three pages with vanilla connector arguments.

PLEASE, next time respect the other threads that have nothing to do with what you are like to discuss!