samba precondition

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Stefan Petersen spe at stacken.kth.se
Fri Aug 19 09:48:25 UTC 2011


On 08/19/2011 09:04 AM, Sylvain Munaut wrote:
> Hi,
[snip]
> Maybe we should check if a pullup on PA0 fixes the other board that
> had troube with SAM-BA, and if it's the case, just add it ... better
> be safe than sorry IMHO. (even if it's troubling not understanding
> _why_ ...)

Hello!

First of all, I agree with Sylvain, better be safe than sorry. If you
are reworking the boards anyhow, add resistors from PA0-PA3 to 3.3V
(100k?). Also add a resistor from ground to the TEST pin (also maybe
100k?). If it doesn't help or screw things up, just don't mount them.

In my designs I usually add a No Mount resistor to every not used pin of
the MCU. Easier to patch in a wire if you screw up and floating pins
makes me nervous. I am a big fan of 0 ohm and Not Mount resistors.

I have previous experience with SAM7 and SAM-BA, a board for a customer
that has been produced in 3 batches of 15 boards each.

First step is to load SAM-BA onto the board. The sequence I have found
working was:
1) Press and hold TEST
2) Generate a reset, by pressing and releasing the reset button.
3) Keep TEST pressed at about 20 seconds. If you feed power from an
external supply you can see a change in current consumption when SAM-BA
is done. Atmel says 10 seconds, but I think it is more.

I then use serial download with Atmels own SAM-BA program (yes Windows
in a VirtualBox). In the latest production batch (<6 months ago) of my
boards there was a new version of the SAM7S with a C tucked on in the
end (if I remember correctly). When I tried to download a program it
said it was OK, but then the program was never written into the flash.
After a long investigation I realized that it required a patch from
Atmel for their SAM-BA program. That patch was not available from any
website by then, but when I asked their support why it did not work they
sent me the patch with an explanation. I can post it here if anyone is
interested.

We have also had problems with too small (physical outline) crystals,
since they seems to have a too long startup time for SAM-BA. Should not
be a problem here though.

OK that was long, sorry. But my maybe there is a crumble in there that
might solve your problem or gives you an epiphany.

Best regards,
/Stefan




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