Small JTAG connector

[MarkR42]

I'm a bit late to this thread...

If you can put the connection at the edge of a PCB, use the amazing soicbite https://github.com/SimonMerrett/SOICbite which has a BOM cost of $0 and the test-clip is very cheap indeed.

It works reliably for me (not for JTAG, for other protocols) and has 8 connections, enough for a typical jtag.

[I wanted a rude username]

Guys in China do everything instantly and sell on Aliexpress.

Ooh, they also have the "Goldilocks" 1.5 mm pitch clips! Metric and large enough to comfortably route a trace between neighbouring through-holes.

https://www.aliexpress.com/item/1005001419056138.html (note: new seller, no feedback)
https://www.aliexpress.com/item/4000852156565.html

[aandrew]

0.050" 2x5 is the way to go. shrouded or non, depending on size.

Stay the hell away from that garbage tag-connect. If you want to actually debug with one of those you either have to use the retainer clip, which works loose over time and drives you mad with frustration, or you use the one with the plastic "clip" feature that needs four gigantic holes around the copper pads to grab on to, negating any advantage over the absolutely bog-standard 2x5, 0.050" header. Save your money and avoid that bullshit.

If you really want a zero PCB cost solution, use something like isptouch (https://github.com/daspilker/ISPtouch, unfortunately the page showing the pic has gone 404 but luckily web archive has it: https://web.archive.org/web/20170719050318/http://www.daniel-spilker.com/blog/2011/04/25/isptouch-for-avr-microcontrollers/)

Don't give tag-connect your money. it's a non-solution to a problem.

[ataradov]

I don't  understand what people are doing with their boards. Why do you need this monstrosity with clips? How do you kill your connectors?

When I work on a project, the debugger is plugged in once and stays plugged in for days and weeks. I'd rather have a small flexible cable plugged into a real connector than this clip with pogo pins that gets in a way or everything. Just imagine the nightmare of having to scope probe around that thing.

And for more small-batch production I just use a hand-made pogo adapter. This one is for 0.1" spacing. And the board just have pads. It is easy enough to hold it for a couple of seconds while target is programmed. 

JPEG failed to attach, so PNG instead.

[Syntax Error]

For anyone still left playing at home, you can make a cheap-n-dirty Jtag/SPI probe from an IDC header and 1mm diameter P100 pogo pins. First, you need to chase out the square holes of the plastic connector with a 0.9mm drill. Then just simply push the pins home. The pins stay held in place. The header can be 6, 8, 10, 12, 20 pins, or whatever. Easy.

Pictured, this header was used to land on a row of Mips ejtag solder domes on a router PCB.

[Kjelt]

Just for information:
https://www.allaboutcircuits.com/technical-articles/jtag-connectors-and-interfaces/

[gmb42]

Via Hackaday, another attempt at an edge connector variant: Debug Edge.

[poorchava]

I use Wurth Elektronik SKEDD IDC connectors. Not small, but I can design a board in such a way, that the debug port is sticking out and is then cut off or broken off in production.

Another option that I use is just incorporating it into bed of nails tester and forgetting about the connector altogether.

[ajb]

Another option that I use is just incorporating it into bed of nails tester and forgetting about the connector altogether.

Yes, I've settled on doing test points as 1.5mm round pads on a 2mm grid, which is a pretty good compromise of density and accessibility.  The signals I will want regular access to for development go along one edge so I can solder on a 2mm header, and I use a 2mm stacking header to marshal flying leads into one thing I can plug and unplug from the board easily.  I have a handful of squid adapters for SWD, UART, etc that have contacts suitable for the 2mm headers so it's easy to put together a debug harness. 

That said, I'll still place a 50mil 2x5 SWD header where I can.  I've been using a three-hole 100mil header pattern with some kinked pin connectors I made for debug UART, but starting with my next board I think I'll put debug UART signals on a couple of the spare pins on the SWD header.

[I wanted a rude username]

Via Hackaday, another attempt at an edge connector variant: Debug Edge.

Note that edge connectors generally have relatively high insertion force. Also, the 1 mm pitch edge connector linked to from the Hackaday article is rated for all of five cycles!

Pogo pins are hard to beat for this application.

[rvalente]

I was looking for 2x5 50mil headers on digikey and they are THAT expensive?

TMS-105-02-G-D https://br.mouser.com/ProductDetail/Samtec/TMS-105-02-G-D?qs=0lQeLiL1qyaWqHDjJyuw0g%3D%3D

$1.17 is little to much for such a simple mass produced thing

[ataradov]

All connectors on DK and such are overpriced.

Direct from China will give you much better prices. And connectors are not that high tech to screw up.

[S. Petrukhin]

I use Wurth Elektronik SKEDD IDC connectors. Not small, but I can design a board in such a way, that the debug port is sticking out and is then cut off or broken off in production.

Another option that I use is just incorporating it into bed of nails tester and forgetting about the connector altogether.

How long have you been using them? How many connections can they withstand?
I ordered a sample pn 490107670612 - it looks very good.

[S. Petrukhin]

Wurth Elektronik SKEDD IDC came to me. A very good connector, definitely. Gold-plated contacts of an interesting shape. But I am sure that this connector cannot be used as a basis for test connections and programming. The pins are very tight in the holes, this is not designed for multiple connections - they will simply tear the metallization at the edges of the hole. Once or twice, I think, normally, no more.

But i immediately tried to cross the snake and the hedgehog: installed pogo pins. It didn't work out. First, pogo pins of the E format didn't fit-their heads stick out, and the connector should sit close. Pogo pins of the F format with the absence of a head also did not fit - plastic guides have a fixing protrusion and it is very weak, 8 pogo pins push out the connector with their springs. 

[Doctorandus_P]

I like the model of the tag-connect connectors but am offended by their price.

If you put test pads on your PCB and some aligning holes similar to the tag-connect idea and the holes are on a 4.54mm grid then you can easily make a test adapter from two pieces of matrix board, a few pogo pins and some stiff wires to align it through the holes.

[IDEngineer]

I don't understand all the hate for Tag-Connect. We've been using them for years here, both for R&D and Production. They last almost forever, and if you use the "legless" versions they consume very little space on the board. Yes, they cost a few bucks, but as noted they last a very long time (I don't remember ever discarding one) so it's basically a one-time tooling cost. We just purchased two more of a particular version of the "legged" variety and I think they were $36 from DigiKey. Normally we order direct from Tag-Connect but we had an R&D order going in to DigiKey anyway so it was just easier and likely faster.

I do concede that the retaining clips for the "legless" versions wear out with repeated insertion cycles. We've never discarded one that I know of but we do have one of the original metal ones whose retention is starting to weaken. That said, I still use it every day (which is how I know about its status) and it's still working for my needs. I can imagine discarding it in a few more months but they cost what, $5? For 5+ years of daily R&D use that's not bad.

Yes, we could make something similar on our own. But for $36 over a lifespan of at least five years, why bother? That's not a good use of personnel time.

[gussy]

Try using the legless version on a product where you can't get the retainer behind the PCBA, or getting a TagConnect cable quickly anywhere in Asia

I've watched a firmware team endlessly fumble with all kinds of contraptions involving rubber bands, tape and weights, to try and get their tag-connects to stay seated. Obviously if you can't use the retainer, you should use the comically large version with the legs that always snap off, but the previous EE was set on tag-connect and didn't have space for the holes (and the legs always snap off anyway).

After I joined and watched them struggle for a few months, then with the next revision of our boards I switched back to the standard 1.27mm pitch SWD connector, and every firmware engineer there thanked me.

Support from TagConnect is also quite terrible. It looks like someone came up with the idea 12 years ago then checked out and now it's their retirement income stream. The website looks like it hasn't been updated in years and is a mess to navigate. Want to download some footprints? Surely a company that makes connectors supplies footprints? Of course they do, in a zip file called "CHECK_CAREFULLY_AGAINST_TAG-CONNECT_SPEC_AND_USE_AT_YOUR_OWN_RISK.zip" inside another folder named "CHECK CAREFULLY AGAINST TAG-CONNECT SPEC AND USE AT YOUR OWN RISK". Want an Altium footprint? Sure, just choose one of the ~12 different implementations inside that zip folder, but remember to use them at your own risk. Should you use the "TC2050-IDC" folder, or maybe the "TC2050-IDC probably better" folder? What a joke. I understand that providing footprints for every CAD package is hard, but this is a core part of their business and would take not very much time or money to come up with an official footprint library for all these CAD packages.

Like others have said, the idea is good, but the implementation is outdated and needs work. The complacency of TagConnect makes me wonder why some alternative with good worldwide distribution, simple verified footprints and a cheaper price point hasn't been created? Probably because most people designing high-volume products just use the standard connectors

[IDEngineer]

With all due respect, that is diametrically opposite of my experience with them. I've had a few questions along the way and when I've called them I've ended up talking with the folks actually designing their products, in some cases even being sent prototype drawings of not-yet-released products. We're a small company and don't buy that much so it's not like we get special treatment.

I'm sorry you're having such bad experience with them but I feel like I need to say it's not always like that. I can't explain the difference but what you're describing sounds nothing like the company I've dealt with. I guess YMMV.

[gussy]

Of course. These are just my own experiences and I'm sure others like yourself have had nothing but good experiences. Like you say YMMV. For what it's worth, I was a huge fan of the product for personal projects until I started using it in production on high volume products, then I got burnt and saw others frustrated with them on a daily basis.

My comments about support mostly surround the laughable zip file of footprints they provide. Providing 12 to 15 different Altium footprints for the same connector and going as far as to label one as "probably better" is unacceptable IMO. It would be better if they provided no footprints instead of the confusion that is offered up. They're running a business, I assume/hope they make good margin on their products, they could hire some contractors to create verified footprints in every CAD package they can think of and I doubt it would cost very much. Not doing so and providing these crowdsourced unverified footprints just makes the whole outfit look unprofessional.

In our case at work we likely saved (insignificant amounts of) money by moving away from tag-connect. $40-50 per cable plus a spare or two for 10 firmware+test engineers every 6 months buys you a lot of 2x5 pin headers.

[tszaboo]

TagConnect is a small family business. Yes, it costs more than making the cables, because they live by selling these. Feel free to copy it and market it, I'm sure its not rocket science, see how your business goes.
They dont have Altium, probably the footprint was someone's own contribution, free of charge. You can order it from Digikey. It works, we programmed thousands of boards with one cable without replacing it. What else do you want? If you dont like it, simple, there are other connectors.

[jnz]

Another tag connect here. Just do it, be cool like us.

[fcb]

We've been using TagConnect since it was introduced. Bloody brilliant.  Still using the original TagConnect cables, and have done countless designs for us and clients using them. Zero problems. Zilch.

We use both the latched (for development and if we've got space) and latchless designs (usually for production and tight boards). As for cost - irrelevant, they've got to eat too. Never damaged an electrical pin, stainless guide pin or latch-leg.

[Bassman59]

My comments about support mostly surround the laughable zip file of footprints they provide. Providing 12 to 15 different Altium footprints for the same connector and going as far as to label one as "probably better" is unacceptable IMO. It would be better if they provided no footprints instead of the confusion that is offered up. They're running a business, I assume/hope they make good margin on their products, they could hire some contractors to create verified footprints in every CAD package they can think of and I doubt it would cost very much. Not doing so and providing these crowdsourced unverified footprints just makes the whole outfit look unprofessional.

How hard is it to make a footprint in your preferred EDA package?

[IDEngineer]

Can't be that hard. Our PCB Designer did it in about five minutes. When we first started looking into these connectors and I asked him about getting the footprint he said "Already finished."

EDIT: And to be honest, creating footprints is just a part of the business these days. There are plenty of "standard" footprints out there but manufacturers seem to feel no loyalty to them. We just got burned by that again on our last board... the spec sheet description claimed it was a "standard 8-SOIC" so our designer just grabbed that footprint from the library, but when the boards got to the pick-and-place guys they said "Umm, this isn't a standard". And they were right. We have a new policy now, we review ALL footprints no matter what the spec sheets claim. Just another part of doing business. So having to create a footprint for a program/debug connector is really a non-event.

[Bassman59]

Can't be that hard. Our PCB Designer did it in about five minutes. When we first started looking into these connectors and I asked him about getting the footprint he said "Already finished."

I should say that I just did a small board with the legged TagConnect. One of the Kicad librarians had created a series of TagConnect footprints, one for each size (2030, 2050, 2070) with the legs, and one set without. There's also one for the 2050 that has a keep-out on the bottom layer for their funny retaining clip thing. I checked the 2050 I used against the data sheet drawing and saw that it matched, and the board works.

I think next time I'll go with the no-legs version and get the bottom clip. The legs break too easily, which is my only complaint.