If you've found your way here, it's likely because you updated your firmware and, despite best efforts to minimize the possibility,something went wrong. Thankfully, most Chromebooks can be easily unbricked using cheap, readily available hardware: older Chromebooks using a ch341a USB programmer from Amazon/eBay/Alibaba (and many other sources), and newer (2017+) Chromebooks using a USB-C debug cable (aka Suzy-Q cable).

Contents

Unbricking/Flashing with a CH341a USB programmer

Requirements

These devices all use a WSON-8 flash chip, which does not expose the pins of the chip, so they cannot easily be "clipped" like a SOIC-8 chip. While it is usually possible to modify a SOIC-8 chip clip to attach to a WSON-8 chip, it's less than ideal. Both Chromebook Pixels feature a Google debug header, which can connect to a debug servo with a special cable and be flashed that way, but not an option for most users (I however do have access to one, and can unbrick Chromebook Pixels for any users upon request).

These 3 components are often bundled together at a lower cost (Amazon link), and if you're unsure if your device uses a 1.8v flash chip or a 3.3v one, it makes sense to have the adapter on hand if needed.

Hardware Disassembly

While this is somewhat device-specific, the main points are the same:

Most ChromeOS devices use a Winbond flash chip, though some use a compatible chip from another manufacturer, eg Gigadevices. It will be either an 8MB or 16MB chip, with the identifier W25Q64[xx] (8MB) or W25Q128[xx] (16MB) where [xx] is usually FV or DV. We do not want to touch the EC firmware chip, which is identified by W25X40[xx].
Unfortunately, many devices have the flash chip located on the top side of the main board, and require fully removing the main board in order to flash. This is true for most Baytrail and Braswell models.

Pin 1 of the flash chip will be notated by a dot/depression on the chip; be sure to align this with pin 1 on the chip clip wiring (a red strip on the example linked above).

Googling should locate a disassembly guide for most models. If you can't find one for your exact model, try to find one for another model of the same manufacturer as the bottom cover removal tends to be very similar.

Prepping to flash

Once you have your device disassembled and flash chip located, time to boot up the flashing environment. Most any Linux setup should do as long as either flashrom is available from the distro's software repositories, or it's 64-bit x86 (in which case you can download a statically compiled build of flashrom from my site). This guide will use a Ubuntu 23.04 live session booted from USB.

So let's get to it:

cd;
sudo apt update
sudo apt install flashrom
Ch341a annotated.png
 : SOIC-8 chip.jpg
sudo flashrom -p ch341a_spi
Flashrom will produce output identifying the flash chip. If it doesn't, double check your connections to the programmer and the chip clip and retry.
Flashrom chip detect.png
Depending on your desired use for the device, you have 3 options for flashing:
- The backup file of the stock firmware created by my Firmware Utility Script
If using this, simply copy the file from USB into the home directory of the live USB user
- The custom UEFI firmware for the device
If you were flashing the UEFI firmware when things went sideways, then that's the easiest way to proceed. You can download the UEFI firmware for your device by examining the sources.sh file from the Firmware Utility Script github repo. Simply concatenate the device-specific filename to the Full ROM base path:
 wget <Full ROM base path><device specific filename>
eg for the Acer Chromebook 14 CB3-431 (EDGAR)
wget https://mrchromebox.tech/files/firmware/full_rom/coreboot_tiano-edgar-mrchromebox_20180827.rom
Don't forget to get the sha1 file for verification:
wget https://mrchromebox.tech/files/firmware/full_rom/coreboot_tiano-edgar-mrchromebox_20180827.rom.sha1
Then verify the download:
sha1sum -c coreboot_tiano-edgar-mrchromebox_20180827.rom.sha1
- The shellball firmware for the device
As with the UEFI firmware above, the shellball rom can be downloaded by concatenating the shellball base path with the device-specific filename:
wget <shellball base path>/shellball.<device name>.bin
eg for the Acer Chromebook 14 CB3-431 (EDGAR):
wget https://mrchromebox.tech/files/firmware/shellball/shellball.edgar.bin

If you're not sure which file to use for your device / don't know your device's board name, you can reference:
https://mrchromebox.tech/#devices and/or http://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices

Persisting the board's Vital Product Data (VPD)

The firmware in all ChromeOS devices contains a section (RO_VPD) which stores board-specific data, like the serial number, localization settings, and on many devices which have an Ethernet port, the LAN MAC address as well. When flashing via the Firmware Utility Script, the script will automatically extract this from the running firmware and inject it into the firmware to be flashed, so the device serial, LAN MAC address, etc are all maintained. Without this, the device will use a default/generic LAN MAC address set by coreboot. While not ideal, this is only really an issue if two or more of the same device are on the same LAN segment (or you're statically assigning IP addresses based on MAC). But for completeness, if flashing the UEFI firmware or shellball ROM, we'll extract the VPD (either from the board itself or a backup made by the script) and inject it into the firmware to be flashed.

NOTE: you don't need to do this if flashing a stock firmware backup created by the Firmware Utility Script; that image already contains the VPD.


For both the options below, we'll need to use the cbfstool (coreboot filesystem) binary, so let's download/extract that:

wget https://mrchromebox.tech/files/util/cbfstool.tar.gz && tar -zxf cbfstool.tar.gz

Option 1: extract VPD from the firmware on device

sudo flashrom -p ch341a_spi -r badflash.rom
./cbfstool badflash.rom read -r RO_VPD -f vpd.bin

Option 2: extract VPD from stock firmware backup created by Firmware Utility Script (this assumes the file has been copied into working directory)

./cbfstool stock-firmware-<devicename>-<date>.rom read -r RO_VPD -f vpd.bin

Then we inject the VPD into the firmware image to be flashed.

./cbfstool <Shellball ROM/UEFI Full ROM filename> write -r RO_VPD -f vpd.bin

Now the firmware image is ready to be flashed, and will maintain the device's unique serial, LAN MAC address, etc.

Flashing Your Device

Now that everything is prepped, time to flash the device. To be thorough, we'll perform a 2nd verification after flashing to ensure the integrity of the flashed firmware.

If flashing your own backup created by the Firmware Utility Script (or any backup made from a live system), use
sudo flashrom -p ch341a_spi --ifd -i bios -w <filename>
otherwise use
sudo flashrom -p ch341a_spi -w <filename>
Where <filename> is the name of your backup file, UEFI firmware file, or shellball firmware file. This will usually take 30s-90s to complete; flashrom will first read the flash chip, determine which sectors differ, erase those sectors, write the new data, then verify the data written.
Even though flashrom does this as part of the write process, verifying the entire flash chip is quick and an easy way to ensure everything went as it should:
As before, if flashing your own backup created by the Firmware Utility Script (or any backup made from a live system), use
sudo flashrom -p ch341a_spi --ifd -i bios -v <filename>
otherwise use
sudo flashrom -p ch341a_spi -v <filename>
using the same filename as before. If the verification passes, then disconnect the CH341a from the host machine, and then remove the chip clip.

Clean Up

Reassembly is the reverse of disassembly. Reconnect the internal battery and replace the bottom cover. Flip over the device, connect external power, press the power button, and cross your fingers :)

Unbricking/Flashing with a Suzy-Q cable

Requirements

Hardware Disassembly

As above, this is only needed if you failed to factory reset the CCD flags as part of disabling the device's firmware write-protection. While this is somewhat device-specific, the main points are the same:

Prepping to flash

Most any 64-bit Debian/Ubuntu based distro should work here, but this guide will use a Ubuntu 2304 live session booted from USB (since its version of flashrom supports Suzy-Q flashing).

Let's get to it:

cd;
sudo apt update
sudo apt install flashrom
ls /dev/ttyUSB*
This command should return 3 items: ttyUSB0, ttyUSB1, and ttyUSB2
If not, then your cable is connected to the wrong port or is upside down; adjust and repeat comment until output is as expected
echo "ccd open" | sudo tee -a /dev/ttyUSB0 > /dev/null
Depending on your desired use for the device, you have 3 options for flashing:
- The backup file of the stock firmware created by my Firmware Utility Script
If using this, simply copy the file from USB into the home directory of the live USB user
- The custom UEFI firmware for the device
If you were flashing the UEFI firmware when things went sideways, then that's the easiest way to proceed. You can download the UEFI firmware for your device by examining the sources.sh file from the Firmware Utility Script github repo. Simply concatenate the device-specific filename to the Full ROM base path:
 wget <Full ROM base path><device specific filename>
eg for the Acer Chromebook 14 CB3-431 (EDGAR)
wget https://mrchromebox.tech/files/firmware/full_rom/coreboot_tiano-edgar-mrchromebox_20180827.rom
Don't forget to get the sha1 file for verification:
wget https://mrchromebox.tech/files/firmware/full_rom/coreboot_tiano-edgar-mrchromebox_20180827.rom.sha1
Then verify the download:
sha1sum -c coreboot_tiano-edgar-mrchromebox_20180827.rom.sha1
- The shellball firmware for the device
As with the UEFI firmware above, the shellball rom can be downloaded by concatenating the shellball base path with the device-specific filename:
wget <shellball base path>/shellball.<device name>.bin
eg for the Acer Chromebook 14 CB3-431 (EDGAR):
wget https://mrchromebox.tech/files/firmware/shellball/shellball.edgar.bin

If you're not sure which file to use for your device / don't know your device's board name, you can reference:
https://mrchromebox.tech/#devices and/or http://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices

Persisting the board's Vital Product Data (VPD)

The firmware in all ChromeOS devices contains a section (RO_VPD) which stores board-specific data, like the serial number, localization settings, and on many devices which have an Ethernet port, the LAN MAC address as well. When flashing via the Firmware Utility Script, the script will automatically extract this from the running firmware and inject it into the firmware to be flashed, so the device serial, LAN MAC address, etc are all maintained. Without this, the device will use a default/generic LAN MAC address set by coreboot. While not ideal, this is only really an issue if two or more of the same device are on the same LAN segment (or you're statically assigning IP addresses based on MAC). But for completeness, if flashing the UEFI firmware or shellball ROM, we'll extract the VPD (either from the board itself or a backup made by the script) and inject it into the firmware to be flashed.

NOTE: you don't need to do this if flashing a stock firmware backup created by the Firmware Utility Script; that image already contains the VPD.


For both the options below, we'll need to use the cbfstool (coreboot filesystem) binary, so let's download/extract that:

wget https://mrchromebox.tech/files/util/cbfstool.tar.gz && tar -zxf cbfstool.tar.gz

Option 1: extract VPD from the firmware on device

sudo flashrom -p raiden_debug_spi:target=AP -r badflash.rom
./cbfstool badflash.rom read -r RO_VPD -f vpd.bin

Option 2: extract VPD from stock firmware backup created by Firmware Utility Script (this assumes the file has been copied into working directory)

./cbfstool stock-firmware-<devicename>-<date>.rom read -r RO_VPD -f vpd.bin

Then we inject the VPD into the firmware image to be flashed.

./cbfstool <Shellball ROM/UEFI Full ROM filename> write -r RO_VPD -f vpd.bin

Now the firmware image is ready to be flashed, and will maintain the device's unique serial, LAN MAC address, etc.

Flashing Your Device

Now that everything is prepped, time to flash the device.

If flashing your own backup created by the Firmware Utility Script (or any backup made from a live system), use
sudo flashrom -p raiden_debug_spi:target=AP -i SI_BIOS -w <filename>
otherwise, if using a UEFI Full ROM image or shellball/recovery-extracted image, use
sudo flashrom -p raiden_debug_spi:target=AP -w <filename>
Where <filename> is the name of your backup file, UEFI firmware file, or shellball firmware file. This will usually take 3-5 mins to complete; flashrom will first read the flash chip, determine which sectors differ, erase those sectors, write the new data, then verify the data written. The initial CCD setup make take a minute or so and not show any progress.

Clean Up

Once flashing is complete, disconnect the Suzy-Q cable. If the internal battery was not disconnected, the device will likely reboot as soon as flashing has completed. If the internal battery was disconnected, reconnect it and replace the bottom cover. Flip over the device, connect external power, press the power button, and cross your fingers :)