Posted on 08/03/2017 by Robert Foss
Before being able to write firmware data to any production Chromebook device, the Write-Protect screw has to be removed.
This post will look specifically at removing the WP screw from a Chell (HP Chromebook 13 G1) device, and verifying that it has been successfully removed.
To actually flash firmware to Chromebook machines, a device called a Servo is needed. While these devices aren't available publicly, they can be produced freely or possibly requested from Google if you are contributing code to the ChromiumOS project.
So this is what the WP screw looks like on a Chell Chromebook. This may or may not be what you will find in other devices. But if you take a close look, you will notice that the copper pad that the the screw attaches against is split into parts that are bridged by a screw being inserted.
So this is the part that requires a Servo device. And a ChromiumOS checkout, for some help setting one up, have a look at my previous post.
# Go to your ChromiumOS checkout cd /opt/chromiumos # Enter dev environment cros_sdk # Set device variable export BOARD=chell # Connect to Chromebook using a Servo device sudo servod -b $BOARD & # Disable WP # This step may vary depending on the hardware of your actual Chromebook dut-control fw_wp:off sudo /usr/sbin/flashrom -p ft2232_spi:type=servo-v2 --wp-disable sudo /usr/sbin/flashrom -p ec --wp-disable |
ChromiumOS Servo
Setting up a ChromiumOS dev environment
This post has been a part of work undertaken by my employer Collabora.
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Comments (8)
Michael A Hall:
Jan 15, 2018 at 09:33 PM
Can you replace the screw after flashing?
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Robert Foss:
Jan 16, 2018 at 03:16 PM
Hi Michael,
Yes you can! As far as my experience has been, the screw only protects against writes.
If there write have already happened, you're good.
Rob.
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Conundrum:
Feb 14, 2018 at 09:28 AM
Hi, yes this is by design to prevent malware messing with the unit.
Unfortunately it also makes repairs harder, if the uEFI gets corrupted the unit is bricked until opened, screw removed and re-flashed.
I did look into using a "magic" SD card as a workaround, as some netbooks can be jigged using a BIOS update that enables the missing function, essentially it stores the boot sector in high memory > 2MB and provides a "boot SD" option.
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lloyd:
Feb 22, 2018 at 04:17 PM
where wp screw on hp chromebook 11.6 v020wm
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Robert Foss:
Mar 01, 2018 at 07:13 AM
Hey Lloyd,
No, unfortunately I don't have access to that hardware or documentation for it.
If you look at the PCB the WP-screw will likely have a split exposed copper ring, which the metal screw bridges.
Rob.
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AG:
Feb 26, 2018 at 12:55 AM
DO YOU KNOW WHERE IS THE write-protect screw chromebook lenovo n21 PLEASE HELP ME
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Robert Foss:
Mar 01, 2018 at 07:13 AM
Hey Ag,
No, unfortunately I don't have access to that hardware or documentation for it.
If you look at the PCB the WP-screw will likely have a split exposed copper ring, which the metal screw bridges.
Rob.
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Gavin:
Apr 26, 2018 at 04:43 AM
Does anyone know where the write-protect screw is on the lenovo n23?
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