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.
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-dev... [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-banan... [5] http://www.digikey.nl/product-detail/en/5250/501-1311-ND/745102
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-Ra.... 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-dev... [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-banan... [5] http://www.digikey.nl/product-detail/en/5250/501-1311-ND/745102
John,
Yes, u37 looks like it.
thank you so much for your helpful advice! I'm up and running again and very happy.
For the record: I put what I did for my specific model on http://opensource.holgerbrunn.net/debian-on-acer-cb5#unbricking
I seem to have done something stupid when shorting the three pins supposed to be connected to 3.3V, this didn't work. But when I disconnected the first pin and connected the other to the second 3.3V on the PI, the chip was recognized. Is it safe to propose the same to other people or was it beginner's luck I didn't damage anything with this wiring?
Regards, Holger
Yes, u37 looks like it.
thank you so much for your helpful advice! I'm up and running again and very happy.
No problem.
For the record: I put what I did for my specific model on http://opensource.holgerbrunn.net/debian-on-acer-cb5#unbricking
I seem to have done something stupid when shorting the three pins supposed to be connected to 3.3V, this didn't work. But when I disconnected the first pin and connected the other to the second 3.3V on the PI, the chip was recognized. Is it safe to propose the same to other people or was it beginner's luck I didn't damage anything with this wiring?
No, generally you don't need to short the 3 pins. In fact the second 3.3v you connected may not have been necessary either. I haven't damaged any of the Chromebooks I've had doing that, and I must've had about a dozen at this stage.
Regards, Holger
Regards,
John.
-
Holger Brunn -
John Lewis