[coreboot] unbricking an Acer CB5

[John Lewis]

On 2015-09-06 17:52, Holger Brunn wrote:
> Dear readers,
> 
> I played with compiling my own coreboot image for my Acer CB5 [1] and 
> failed
> miserably - the bios is messed up and the device won't boot any more. 
> Now I'm
> busy following some guides to undo the damage [2], [3] by flashing the
> original bios again, but given I'm quite clueless about hardware, I'd 
> like to
> ask you for advice about how to proceed:
> 
> I ordered a Raspberry PI, some connector cables [4], and then I 
> probably need
> a clip to connect the chip [5].
> 
> My question to you is how to locate the chip? The mainboard looks like 
> that:
> http://opensource.holgerbrunn.net/debian-on-acer-cb5/images/DSC01629.JPG 
> and
> the only chip that looks like those in the examples is U37 in the lower 
> right.
> Is there any way to know beforehand if it's the correct one? And then 
> when
> connecting the pins, can I look up somewhere what the correct 
> assignment is or
> is this trial and error? I can't read what is printed on it, but if 
> relevant,
> I'll get a magnifying glass to post the text.

Yes, u37 looks like it. But, bear in mind many Chromebooks have the SPI 
on the other side of the board. If the chip is the wrong size (early 
Chromebooks had a separate EC on a 512k SPI) Flashrom will crap out and 
complain when you try to flash an 8MB binary to it. Pin assignment is 
available in various articles on the web, this is one I found by 
searching - 
https://github.com/bibanon/Coreboot-ThinkPads/wiki/Hardware-Flashing-with-Raspberry-Pi. 
I have used a magnifying app on my smart-phone before, but it's 
unnecessary.

HTH,

John.

> 
> Thank you a lot in advance, and be sure that I won't come back whining 
> if
> anything goes wrong and I fry the chip following your advice - that's 
> entirely
> my fault then.
> 
> I'll log the process on the above website if successful so that the 
> next
> person messing this up won't have to bother you.
> 
> Regards,
> Holger
> 
> Links:
> [1]
> https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/acer-cb5-311-chromebook-13
> [2] 
> http://www.tnhh.net/2014/08/25/unbricking-chromebook-with-beaglebone.html
> [3] https://johnlewis.ie/unbricking-a-samsung-series-5-550-chromebook
> [4]
> https://www.conrad.nl/nl/raspberry-pi-verbindingskabel-rb-cb5-025-bont-banana-pi-pcduino-arduino-raspberry-pi-a-b-b-1290220.html?sc.ref=Homepage
> [5] http://www.digikey.nl/product-detail/en/5250/501-1311-ND/745102