XCORE-200 USB breaks on my custom board

Technical discussions around xCORE processors (e.g. General Purpose (L/G), xCORE-USB, xCORE-Analog, xCORE-XA).
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ccrome
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XCORE-200 USB breaks on my custom board

Postby ccrome » Fri Feb 10, 2017 7:39 pm

Hi there,
I'm having a problem with my custom XCORE-200 boards. The USB works for a bit, then breaks. I have swapped the XMOS chip out, and again, it works, then breaks.

I'm following the reference design pretty closely, but there is one, perhaps substantial difference in power supply sequencing.

I have the 3.3V bus go high with VBUS, but then the sequencer doesn't power up the 1.0V supply for 15mS. And reset doesn't get released for another 15mS.

So, the power sequence is:

VBUS -> HIGH @ T=0
3.3V -> HIGH @ T=1mS or less.
1.0V -> HIGH @ T=15mS. The actual ramp time is quick -- < 1mS
POW -> RELEASED @ T=30mS

Could this be the source of my problems?

The spec says 1.0V must ramp to high within 10mS, but where is that measured from? 10mS of monotonic ramp from 0V -> 1.0V, which is what I assumed. If it's 10mS from when 3.3V is high, then that could be a problem.

Strangely, this board worked for a good long while with no issues, but then broke and never got better.

The only thing I can think of is that I may have used a laptop when everyting worked, then moved to my desktop which broke things.

Thanks,
-Caleb
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ccrome
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Postby ccrome » Fri Feb 10, 2017 7:41 pm

And by 'Breaks' the symtoms are:

Cannot ennumerate. I get error messages reading the descriptor. Then just nothing -- no response or logs from the host -- the host doesn't recognize that an attach event happened, yet I can still access the chip from JTAG, run code, and everything.
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mon2
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Postby mon2 » Fri Feb 10, 2017 11:36 pm

Hey Caleb. Do you have power sequencing circuits to monitor each power rail ? Can you post your schematic for the relevant power supply ?

There are some freeware USB monitor tools that can offer an insight to which packets or lack of are being sent by the XMOS CPU.
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ccrome
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Postby ccrome » Sat Feb 11, 2017 12:16 am

mon2 wrote:Hey Caleb. Do you have power sequencing circuits to monitor each power rail ? Can you post your schematic for the relevant power supply ?

There are some freeware USB monitor tools that can offer an insight to which packets or lack of are being sent by the XMOS CPU.
I just replied to the other thread here: http://www.xcore.com/viewtopic.php?f=7&t=5589&e=1.

I guess we can just stick to that one...

http://www.xcore.com/viewtopic.php?f=7&t=5589&e=1

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