Acer C720 Chromebook

Warning
This article relies on third-party scripts and modifications, and may irreparably damage your hardware or data.
The Acer C720 Chromebook (and newer Chromebooks in general) features a "legacy boot" mode that makes it easy to boot Linux and other operating systems. The legacy boot mode is provided by the
SeaBIOS
payload of
Coreboot
. SeaBIOS behaves like a traditional BIOS that boots into the MBR of a disk, and from there into your BIOS-compatible
boot loaders
.
Installation
Go to the
Chrome OS devices
page, read the
Introduction
and continue by following the
Installation
guide.
Configuration
For information on general Chromebook post installation configuration (hotkeys, power key handling ...) see the
Post installation configuration
on the
Chrome OS devices
page.
Touchpad Configuration
See the
libinput
article on how to install and setup your touchpad.
Improving WLAN and BT performance
The C720 comes with Atheros AR9462 WLAN and Bluetooth chip which is supported by the
ath9k
kernel module, the following
kernel module parameters
to the
ath9k
module can help to affect the performance, quality and power consumption of the chip.
/etc/modprobe.d/ath9k.conf
options ath9k bt_ant_diversity=1 ps_enable=0
Details of possible settings are below.
Bluetooth coexistence
Both Bluetooth and WiFi can use 2.4 GHz, which can cause interference. You can enable Bluetooth coexistence to improve the performance of the card with the parameter
btcoex_enable=1
.
Power saving
You can enable power savings with the option
ps_enable=1
to reduce power usage, though it has been
suggested
that enabling it might be related to system freezes and also to dropouts so if you encounter such issues then you might want to make sure it is disabled (
ps_enable=0
).
Improving signal quality
Enable antenna diversity with the option
bt_ant_diversity=1
to improve the signal quality and boost performance. However, keep in mind that
this disables the bluetooth interface
and, as such, bluetooth coexistence  must not be loaded at the same time.
Fixing decrease in bandwidth
If you are experiencing a decrease in bandwidth at seemingly random times try switching from hardware to software wireless encryption as explained in
Wireless network configuration#ath9k
.
Suspend
Fix wakeup from suspend on lid close
When the lid of the C720 is closed, the top of the screen presses against the touchpad, instantly waking the computer from suspend. To disable wakeup by touchpad, create the following file:
/etc/tmpfiles.d/disable-touchpad-wakeup.conf
w /proc/acpi/wakeup - - - - TPAD
To check the current state:
# grep TPAD /proc/acpi/wakeup
Alternatively, it may be toggled manually by running:
# echo TPAD > /proc/acpi/wakeup
This method does not persist after a reboot.
Lots of ehci errors in dmesg after resume
See
Chrome OS devices#Fixing suspend
.  Additionally,
[1]
,
[2]
,
[3]
, and
[4]
may be helpful.
One symptom may be that it cannot properly shut down or reboot.
Locating the Write-Protect Screw
Remove the bottom panel of the laptop by removing the 12 visible screws and another one underneath the warranty sticker.
Separate the plastic starting at the back.
Remove completely the write-protect screw from the motherboard, which is labelled as #7 in
this picture
.
Known issues
System freezes
See power saving section at
Improving WLAN and BT performance
.
Additionally see
SSD#Troubleshooting
if the system freezes are associated with hard drive errors in the system's journal.
Internal microphone not working
If your internal microphone is not working, select "Microphone (unplugged)" as your input source in the PulseAudio Volume Control. Your internal microphone should now work.
[5]
See also
Chrome OS devices#Fixing audio
for another possible solution.
System shutdown on battery
If you are on battery and the system shutdown when you use the keyboard, it is probably a battery switch mulfunction (cover do not press it all time), labbeled #5 in
this picture
. It is a safety mechanism to prevent the Acer C720 from being powered by the battery while the cover is removed.
You can bypass this switch with a screw inserted in hole #6.
See also
Chromium OS Acer C720 & C720P Developer Page
BBS topic
Unbricking with
flashrom
using the Raspberry Pi
, requires
SOIC clip
, See
GPIO matrix
and
pictures
. also there is a
BeagleBone method
.
Configuration files with optimization tweaks for Haswell devices used by default in the GalliumOS Linux distribution
.