LOST... XTAG2 Not detecting my device

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Re: LOST... XTAG2 Not detecting my device

Postby segher » Thu Mar 29, 2012 1:28 am

Hi jonecm,

You should have pullup (or down) resistors on the MODE pins, and various
JTAG pins, and the reset pins. You should not rely on the internal pullups
to drive any external circuitry (or even a track on your PCB), they are too
weak for that. Don't let any chip inputs float, and keep in mind you won't
have the XTAG connected to your board in normal operation ;-)

A good way to drive TRST etc. is via open drain gates. Look e.g. at the XK-1
schematics for a good example.

You can check if the core is running by setting it for SPI ROM boot and checking
if there is activity on the SPI then.

My bet what is wrong with your board is the clock; I've seen non-functioning
JTAG on an XS1-L when the clock was bad before. Rather strange, JTAG should
not use the chip clock at all, but perhaps the PLL is triggering TRST when
it doesn't yet have lock, or something.

Good luck,

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Postby jonecm » Thu Mar 29, 2012 5:04 am

Hi everybody, Thanks for all your help, I was able to trace the problem to bad soldering, got that fixed and everything seems to be working except the flash. The idots over at sparkfun screwed up on there XS1-L1 and got a bunch of pins messed up, looks like I will have to get new boards made anyways since it's so screwed.

Still would be interested in feedback from the forum on the best way to do the reset buffering so the PG output from the vreg dosn't fight with the XTAG2

Thanks all!

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Postby jonecm » Sun Apr 08, 2012 6:38 pm

Just thought I'd let everybody know that I posted a project entry https://xcore.com/projects/xmos-xs1-l1-module I'm going to do 2 more prototype orders and then go for a large production run

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