Looking for easy ways to make temporary connections to probe data from pads

[marcosscriven]

I'm looking for different ideas on making temporary connections to pads to sniff data (or even send data) to something like an eMMC (albeit perhaps at its slower 24MHz mode)

Although I'm not using a jtagulator, I Googled images of it to get an idea, and people seem to be using one of:

1: Header already on board
2: Soldering a lead
3: Both soldering a lead, and using a clip:

In my case there's no header, only ~1mm diameter pads (and in one case I'm targetting one end of a tiny SMD resistor).

I found this thing on Ali



But I can't find any reviews or YouTube vids of anyone using something like this, and thus wondering if it's a waste of money (and presumably long delivery time)?

What do folks here use?

[Faranight]

Hello. I'm using probes from Sensepeek.
A bit more expensive than Aliexpress, but well worth the money IMHO.

[Kim Christensen]

The Aliexpress thing looks awkward and only suited for low frequency stuff. If the PCB you are probing has components on the other side, it's not going to lay flat and will "rock" when pressure is applied making the probes slip out of alignment. The Sensepeek posted above looks much better. Depends on how much you want to spend. Soldering a wire on is pretty cheap.

[marcosscriven]

Ah, that looks perfect for my needs Faranight (this forum is awesome)

I think part of the issue here was not being sure what to Google. "probe" is too generic. "flying probe" seemed to be related, but more to do with industrial-level PCB testing. Sensepeek seems to call it "hands-free measurement".

[asis]

Hi,

Look ai this:

...i like this guy

equipment ACElab
https://www.acelab.eu.com/

[Fungus]

(and presumably long delivery time)?

You don't provide a link but Aliexpress has 10 day delivery on just about everything these days.

(and free returns if you don't like it)

[marcosscriven]

Hi,

Look ai this:

Interesting - that looks similar to the clones on ali, although I just want the board (the associated gizmos/software looks great, but expensive).

I'm curious now though because Kim said it looked "only suited for low frequency stuff", but the Ali one looks similar to the one they are using to extract data from an SD card.

[Fungus]

I'm curious now though because Kim said it looked "only suited for low frequency stuff"

Everybody around here has their own personal definition of "low frequency".

1GHz is low frequency to some people.   

but the Ali one looks similar to the one they are using to extract data from an SD card.

They seem to be doing it at around 10MHz clock speed (extracting 5Mb/sec). That seems plausible.

[marcosscriven]

Hello. I'm using probes from Sensepeek.
A bit more expensive than Aliexpress, but well worth the money IMHO.

Just been doing some more investigations on this, and happened upon this tweeted by SensePeek themselves https://twitter.com/SensePeek/status/1543138257571020801 (unfortunately that links to a TikTok vid, ughh)

Anyway, two things struck me about it.

Firstly, in that video the presented demonstrates the pin staying there, but it appears not to. I wonder if he just made a mistake, or it's not as it looks.

Secondly, there's a comment on that video saying "But does it have something to replace the long ground lead. You'll never get meaningful measurements except near DC" - do you know if that's actually an issue?

As I say, I want to be able to use this to read/write an eMMC chip on board, as well as for logic/scope probing.

[mwb1100]

Firstly, in that video the presented demonstrates the pin staying there, but it appears not to. I wonder if he just made a mistake, or it's not as it looks.

There are two instances of "incidental" probe movement I saw in the video:

1. the probe was bumped by the presenter (just before he picked it up to demonstrate placement).  It definitely moved, but I can't imagine anyone expecting that it wouldn't.

2. the presenter placed the probe, and when he released it you can see the main part of the probe move up.  However if you read the details of the probe's design you'll note that it has a "spring-loaded test needle".  Elsewhere on sensepeek's site they say that the "weight of the head makes the compressible needle maintain constant pressure at the probing point".  I think what is seen when the presenter removes his hand is the needle "unspringing".  It should have maintained contact (whether it did, I can't say).

[marcosscriven]

Just for posterity, found yet another option here: https://www.thingiverse.com/thing:3615910/comments


https://hackaday.com/2019/11/15/needling-your-projects-3d-printed-pcb-probing-jig-uses-accupuncture-needles/

No idea how well acupuncture needles would work!?