[Elphel-support] U-Boot ported to Elphel 10373 board (from Elphel Development Blog)

[Andrey Filippov]

(text-only version of the Elphel Development Blog posting -
http://blogs.elphel.com/2009/10/u-boot-ported-to-elphel-10373-board/ )
Finally U-Boot is running on the new board – it took two full days (and
partially -nights) to make that happen. Initially I had no idea what exactly
happened when control was passed to u-boot (I already knew that memory is OK
and the u-boot image ion the board’s memory is the same as generated on the
host and serial port software was under suspicion, so I looked for an
independent (of the UART) way how the software could tell me that it reached
some points. Obvious solution – general purpose I/Os, but unfortunately most
of them are either routed on the inner layers or have multiple functions
(shared I/O pins) – and I did not know if any of the software (ROM boot,
first stage UBL or U-Boot itself) control them. Just one GPIO pin was not
shared and had easy access – connected to the 64-pin QFN package with 0.5mm
pitch pins – pins are on the sides, not under the belly as on the BGA ones,
so I just soldered a wire to that pin and was able to watch it with
oscilloscope.

With that one-bit “printf” life got easier – I was able to find that the
serial port output was the one having problems. In most cases it just
silently got stuck, but sometimes the serial port was sending out 5-bit zero
data (seems like control register that was programmed to 8n1 initially, got
zero written to it and switched to 5n1. I still do not understand what did I
do wrong and why supposedly working software failed in my case. I resolved
the problem by replacing the 8-bit UART registers (separated by 3 dummy
bytes) with the 32-bit ones – same as was done in the first initial
bootloader that I already had working. With that small mystery unresolved
the u-boot is now running as you can see on the screenshot -
http://blogs.elphel.com/wp-content/uploads/2009/10/elphel373_uboot.png.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://support.elphel.com/pipermail/support-list_support.elphel.com/attachments/20091019/6dc8d7cf/attachment-0002.html>