Production SWD/SCLK Multiplexing?

RE: Production SWD/SCLK Multiplexing?

godmode — Sat, 30 Jun 2018 09:08:54 GMT

It is possible.
I have built 48 port SWD multiplexer that runs on 250cm long cables at 4MHz clock programming and debugging.
Please check releated post (text and photos):
devzone.nordicsemi.com/.../what-is-the-swd-driver-impedance-of-swdio-line

RE: Production SWD/SCLK Multiplexing?

slowcoder — Thu, 13 Jul 2017 16:52:28 GMT

If you only considering production testing, here's how it's usually done in high-volume production.

It's not common to test the whole panel with one connector. It sounds like a good idea, but routing traces out from the individual PCBs into the panel is usually a yield-loss drivers, as the traces might (and do) get shorted when you cut or route them out from the panel.

So, if we concentrate on testing a single PCB, there's usually at least four test-points that a "bed of nails" test-jig can attach to. VCC,GND,UART_TX and "TESTMODE".

When the device starts up, it checks the testmode pin, and if it's shorted to ground, the device enters a self-test mode, and outputs the results over UART.

Why is it done this way? Well, UART is the least common denominator when it comes to various embedded devices (anything from 8bit micros to 64bit SOCs support it). Also, a USB<>UART converter is super-cheap, so the factory can buy as many as they need.

RE: Production SWD/SCLK Multiplexing?

endnode — Wed, 12 Jul 2017 14:42:11 GMT

Btw. here is one commercial solution matching your requirements, maybe won't be so expensive... and there must be more.

RE: Production SWD/SCLK Multiplexing?

endnode — Wed, 12 Jul 2017 14:38:56 GMT

Well good luck with that, looks like hazard, hoping you don't get scrapped batch of few K of boars as reward for saving few hundreds $....

RE: Production SWD/SCLK Multiplexing?

Shay Ohayon — Wed, 12 Jul 2017 14:34:45 GMT

I assume I can route UART communication to each of the boards on the panel, so we could get a detailed report on each one of the boards to know what is wrong with them. At least, that was my idea. This is for a somewhat small production (few thousands at the moment), so we don't want to invest in expensive programmers.

RE: Production SWD/SCLK Multiplexing?

endnode — Wed, 12 Jul 2017 14:17:24 GMT

Is your sequence one-way only? If not then this solution doesn't make sense... there are programmers which can operate up to dozens of targets, of course their price goes higher then few hundreds bucks. But still might be worth savings on programmers and time. Have you checked these presented on Infocenter and Blog zone?