[coreboot] [RFC] cheapish and free usb spi flashing device

[Stefan Tauner]

hey there!
(cross-posted to both mailing lists)

i am currently designing a small and cheap platform to recover from
coreboot and other failures easily.
the reason i am writing this is to get feedback from you regarding
desired features of and interest in such a device.

right now my plan is the following:
an avr atmegaXXu2 is connected via usb and implements the serprog
protocol to let flashrom make use of it. the avr can operate down to
3.0V which would allow easy interfacing with today's spi flashes
without any level shifting. to get the desired supply voltage from
usb's 5V i will use a fixed 3.3V ldo voltage regulator (ld1117). apart
from a few supporting parts (caps, fuse, usb line termination etc.) the
only things missing are sockets for the spi chips.

at the moment i am planing to include:
- soic8 pads (combined for 150 and 200mil devices) and enough room for
  a soic8 zif adapter (like the one from http://bios-repair.co.uk)

- vias for a 24 pin zif dip/dil socket (150 and 300mil spacing
  combined): 8 pins for dip8 flashes and 16 for soic16 flashes (those
  would require a soic to dip adapter). 8pin and 16pin flashes dont
  share pins therefore the large socket...

- vias for a single row 8pin header to allow attaching probes/test clips
  (e.g. http://www.pomonaelectronics.com/images/large/6109.jpg) to hook
  up in-situ flashes.

parts for this excluding the pcb would be in the 10-25$ range.
depending on how many pcbs i/we would produce the whole thing would
cost probably about 40$. not THAT cheap, but quite better than
the dediprog stuff :)
it would also be more convenient and open than the FT2232SPI based on
the DLP-USB1232H (http://flashrom.org/FT2232SPI_Programmer). the
willem programmers seem to be lpt only? are there any other cheap
flashers i dont know?

i am not sure about what to do with soic16 chips. the solution laid out
above which requires an additional adapter and wastes a lot of space is
awkward. should i just include soic16 pads instead? should i drop
support for them altogether and let the user hook them up with clips?
are they in use anywhere? my intel desktop board has pads for it, but i
am not sure if there are any boards in the wild which really use them...

i was also thinking about an offline mode which uses an SD-card or
another flash to store/load an image for the target flash. push
buttons would activate a cloning operation. this way one could clone
chips easily without a pc, but i am not sure at all if thats worth it.

what do you think?
-- 
Kind regards/Mit freundlichen Grüßen, Stefan Tauner