Products > Test Equipment

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

(1/32) > >>

oliv3r:
After seeing a couple of great pod designs, I decided I wasn't quite happy with the designs overal.

What I wanted was to use (mini) HDMI cables, as they are cheap, super common and shielded. Also 4 channels per pod had my preference, to make them nice and small.

The design is based on a breakout board, that plugs into the scope, and offers 4 (mini) HDMI connectors. The other end consists of a POD, featuring either a LMH7322 (like the original), LMH7324 (cheaper quad channel part) or SNV65LVDS (much cheaper, less flexible) comparator. Mix-n-match is the keyword here, feel unrestricted in what pod to connect, get 4 LMH7322 based pods, or one of each. In the future, more pods may be added if it makes sense.

As for the breakout board, there's currently two models, both with 50pin IDC connectors, matching the MSO5000 series and DHO900. The mini-HDMI variant was made to offer a super small/narrow profile, which is nice for the DHO900, but either work. In the future, given we have some testers/interest, we can very easily add a 68pin IDC variant for the DS1074 series, and very likely also for the PCIe based scopes such as the DSO7k and MSO8k series.

Some words on the other great designs.
Gandalf_Sr's Budget probe set design.
https://www.eevblog.com/forum/testgear/ms05000-budget-logic-analyzer-probe-set-design/msg2938442/#msg2938442
At first, it seemed like a good idea, but I didn't like that it wasn't open source so couldn't even respin it. Secondly, I liked the idea and even was planning on doing a pod for it, but the SNV65LVDS seemed more sensible at the time.

S. Petrukhin's easy eda low cost probe
https://www.eevblog.com/forum/testgear/low-cost-logic-analyzer-probe-for-rigol-mso5000-easyeda-project/
I really liked this design, but the many small comparators I didn't quite like, nor the flat cable design. But it was the thread that inspired me (after 3 years? to finally make my own design) after the suggestion of the SNV65LVDS. It was open-source though, but easy-eda :(

Nikki Smith's variant
https://climbers.net/sbc/clone-pla2216-logic-probe-analyzer/
Was what really maybe got me moving, as he did the work in KiCad and used the LMH7322 and LMH7324. I really wanted to have balanced lines (lapod all traces are length-matched). But, still wrong connector ;) I was still hung up on the HDMI bit. Also Nikki went silent after september :(

dren.dk's first foss unit
https://gitlab.com/dren.dk/mso5k-la-pod/tree/master
The name was actually inspired from this post https://www.eevblog.com/forum/testgear/rpl1116-active-logic-probe-pod-for-1000z-series-teardown/msg2125477/#msg2125477 :) LA pod. But 8 pins in a pod was not my liking, and flat cables.

thmjpr's USB-C variant
https://gitlab.com/thmjpr/stm32f03_la_monitor
I do like the idea of using USB-C cables, but USB-C cables are a huge pain. are all wires routed, does it have an E chip, will that be in our way. Should we do USB-PD on the breakout board? Also, reversability is cool, but not ideal for the breakout.

One major input for reference was https://www.eevblog.com/forum/testgear/rpl1116-active-logic-probe-pod-for-1000z-series-teardown/ which includes a (measured) breakdown/schematic.

Others I have missed? Regardless. Here's my variant :)

All schematics and stuffs come from the pipeline when released https://gitlab.com/riglol/lapod/-/releases, and I've attached a whole bunch of some WIP stuff here https://www.eevblog.com/forum/testgear/another-low-cost-la-probe-for-rigol-mso5000-by-oliv3r/msg5311123/#msg5311123

Note, that I haven't ordered any PCB's yet, and nothing is tested. It just looks really sexy in the renderings :p


EDIT 2024-02-03: Changed the starting post as we are now our own thread. Find below the remainder of the starting post
(left-over of the original first post)
I am too working on a respin of this :)

mostly, because I wanted to use HDMI cables and 4 channels per pod. Here's my WIP screenshot; but it's far from finished. The pinout of the connector is crazy, causing all sorts of weirdness to be needed in routing bits, and to have at least the easiest routing, the connectors will end up having a weird order, J2, J4, J1, J3, which will translate to port1, will have pins 5 - 8, port2, 13 - 16, port1 1 - 4, port3, 9 - 12, which I admit is a bit odd, but keeps routing sane, or the size down, whichever you prefer.

I'll route the other bits next (which is just power and gnd) and then route the pods.

For those curious, I'll also attach a screenshot of the HDMI pinout to shout and shame :)

ebastler:

--- Quote from: oliv3r on October 06, 2023, 03:38:38 pm ---The pinout of the connector is crazy, causing all sorts of weirdness to be needed in routing bits, and to have at least the easiest routing, the connectors will end up having a weird order, J2, J4, J1, J3, which will translate to port1, will have pins 5 - 8, port2, 13 - 16, port1 1 - 4, port3, 9 - 12, which I admit is a bit odd, but keeps routing sane, or the size down, whichever you prefer.
[...]
For those curious, I'll also attach a screenshot of the HDMI pinout to shout and shame :)

--- End quote ---

Not sure I understand how the pinout of the HDMI connector could drive the need to swap the sequence of the pods. I would expect the HDMI pinout to potentially force an awkward order of the four channels within each pod group, but the pod sequence to follow the order on the scope's connector?

UK:

--- Quote from: oliv3r on October 06, 2023, 03:38:38 pm ---I wanted to use HDMI cables and 4 channels per pod.

--- End quote ---

Why HDMI exactly? Why not RJ-45 LAN cable? Moreover, Cat-7 / 8 cables have superior shielding for each pair, the connector with fixation also may be a very handy feature when a lot of stuff is going on on your table. Also, RJ-45 also has more robust contacts than an HDMI.

oliv3r:

--- Quote from: UK on October 07, 2023, 10:41:06 pm ---
--- Quote from: oliv3r on October 06, 2023, 03:38:38 pm ---I wanted to use HDMI cables and 4 channels per pod.

--- End quote ---

Why HDMI exactly? Why not RJ-45 LAN cable? Moreover, Cat-7 / 8 cables have superior shielding for each pair, the connector with fixation also may be a very handy feature when a lot of stuff is going on on your table. Also, RJ-45 also has more robust contacts than an HDMI.

--- End quote ---

All true, but RJ45 doesn't have enough pins. You can do 4 channels, but then have no power or anything. If you do all power pins, you end up with just 2 channels, which is usable, but leaves a lot to be desired ...

HDMI cables are cheap and easy to get, and give you differential pairs too. The 5V pin is gonna be a challange, as cheap cables will not allow much current to go through, but must let 50ma go through at the very least to pass certification.


--- Quote from: ebastler on October 06, 2023, 03:47:09 pm ---
--- Quote from: oliv3r on October 06, 2023, 03:38:38 pm ---The pinout of the connector is crazy, causing all sorts of weirdness to be needed in routing bits, and to have at least the easiest routing, the connectors will end up having a weird order, J2, J4, J1, J3, which will translate to port1, will have pins 5 - 8, port2, 13 - 16, port1 1 - 4, port3, 9 - 12, which I admit is a bit odd, but keeps routing sane, or the size down, whichever you prefer.
[...]
For those curious, I'll also attach a screenshot of the HDMI pinout to shout and shame :)

--- End quote ---

Not sure I understand how the pinout of the HDMI connector could drive the need to swap the sequence of the pods. I would expect the HDMI pinout to potentially force an awkward order of the four channels within each pod group, but the pod sequence to follow the order on the scope's connector?

--- End quote ---
because the connector's pin-order isn't in sequence :( So i took the effort to make sure that the 4 pins within the HDMI connector are in order, so that took a lot of swapping. But swapping all pins for all connectors just takes way to much PCB space to keep the connector within reasonable size. Also, I wanted to keep the inner layers for power and ground, if I'd put signals on the inner layers, i could have swapped about a little bit more ...

UK:
Okay, now it makes sense. But why not a Mini DisplayPort, it's smaller but has all the same.
Or even a full-size DisplayPort, since it has a fixing feature.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod