SAM9G25 Boot Issues...

Discussion around AT91RM9200 and SAM9 Series Products.

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Posts: 8
Joined: Fri Jan 31, 2014 8:07 pm

SAM9G25 Boot Issues...

Tue Aug 12, 2014 3:34 pm

I'm having trouble bringing up a custom board designed following the AT91SAM9G25-EK schematics.  This is the first spin of this particular design, so there are some things I expect to find wrong with it...

I connect +5V power to the board, and have measured the following:
VDDIOP0 (and 1): 3.34V
VDDNF: 3.34V
VDDBU: 3.34V
NRST: 3.3V

I am attempting to get the processor into SAM-BA mode.  BMS is pulled up to +3.3V (VDDIOP0), and the flash is currently switched "off".

I am fairly certain that I used the wrong crystal for the 12MHz clock, so I expected not to be able to use SAM-BA via USB.  However, I am not even able to see any activity on the DTXD line, where I would expect to see "RomBOOT" printed.

I tried removing the XIN32/XOUT32 crystal in case I had also incorrectly selected that part, but no change.  I'm not sure that it affects anything anyways, since I believe the processor uses the internal 32kHz clock to get started (although I'm not sure if SAM-BA switches to the external 32.768kHz clock).

I also looked at PD4_NANDCS, and I see a ~4ms-wide square pulse (0V -> 3.3V, 4ms, 3.3V -> 0V).  To me, this means that the processor is getting "stuck" when trying to read the NAND flash.  The low-to-high transition is likely the processor receiving power, then the high-to-low is likely the processor trying to read the NAND flash and asserting the chip-select line.  I notice that the RE# line is not being toggled appropriately due to a layout connection error--however, would this cause the processor not to fail into SAM-BA mode?  To me, it seems that the processor should try to assert RE# (PD0), then read the I/O lines and get garbage (the NAND chip is in reset still).

What else is there for me to check?  The power seems good & stable, what else is needed to get into SAM-BA?

Thank you.
Posts: 8
Joined: Fri Jan 31, 2014 8:07 pm

Re: SAM9G25 Boot Issues...

Tue Aug 12, 2014 10:11 pm

Some more information.  Approximately 3ms after power is applied, the NRST line toggles low, then high again on the SAM9G25-EK board.  However, on my board, it seems to "try" to.

Any thoughts as to whether that's indicative of something specific?
Custom board waveform of the NRST line after power-applied.
jmf.png (2 KiB) Viewed 1431 times
SAM9G25-EK board waveform of the NRST line after power-applied.
orig.png (2.15 KiB) Viewed 1431 times

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