Google Nexus 7 2012 (asus-grouper)

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Google (ASUS) Nexus 7 (2012)
Galaxy Nexus 7
Galaxy Nexus 7
Manufacturer Google (ASUS)
Name Nexus 7 (2012)
Codename asus-grouper
Released 2012
Original software Android 4.1.2 on Linux 3.0
Hardware
Chipset Nvidia Tegra 3
CPU Quad-core 1.2 GHz Cortex-A9
GPU ULP GeForce
Display 800x1280 IPS
Storage 8/16/32 GB
Memory 1 GB
Architecture armhf
Features
USB Networking
Works
Flashing
Works
Touchscreen
Works
Display
Works
WiFi
Works
Xwayland
FDE
Mainline
Battery
3D Acceleration
Accelerometer
Audio
Bluetooth
Camera
GPS
Mobile data
Unavailable
SMS
Unavailable
Calls
Unavailable
USB OTG


Contributors

  • antonok
  • pangelo

How to enter flash mode

  • Connect a USB cable
  • Power the device off
  • Hold power + volume down
  • fastboot should work when the green android appears on the screen

Installation process

1 $ git clone https://gitlab.com/postmarketOS/pmbootstrap.git
2 $ cd pmbootstrap
3 $ ./pmbootstrap.py init
4 $ ./pmbootstrap.py install --no-fde
5 $ ./pmbootstrap.py flasher flash_kernel
6 $ ./pmbootstrap.py flasher flash_rootfs

UI options

  • Weston: Boots, but also occasionally reboots on its own.
  • Hildon: Boots into a black screen. Poking some /sys/ variables might make the screen flash or turn on, but it remains unusable
  • XFCE4: Boots into a black screen.
  • Mate: Can't flash. This is due to the .img file being bigger than the system partition size.
  • Luna: Can't flash. Same as Mate.
  • KDE (Plasma-Mobile): Can't flash. Same as Mate. Which in turn wrecks your device partitions. This has happened even with flasher flash_rootfs --partition userdata

Development Notes

Kernel

  • The port is using the LineageOS kernel found here
  • The kernel cannot be compiled on versions of gcc newer than 4.9 without the appropriate patch
  • UART debugging through the headphone jack doesn't seem to work - apparently the 2012 version of the Nexus 7 does not have this feature.
  • This page includes a list of changes to the Android kernel that are not present in mainline Linux.
  • A newer kernel, that should work, can be found here (thanks to Jasper in IRC): https://github.com/Unlegacy-Android
  • The default images for android provided by google have the bootloader broken, meaning it can't be flashed. It does not seem to affect the install process of PostmarketOS, but is something to take into account.

Graphics

  • CONFIG_VT had to be enabled for graphics to work. In menuconfig this is located under Device Drivers -> Character devices -> Virtual terminal.
  • /sys/class/graphics/fb0/mode is empty on boot, it must have U:800x1280p-0. This uses the same initfs hook as many other devices. Update: Seems to be correctly set now
  • xwayland does not work.
  • weston with fbdev-backend.so uses pixman-type=3 (PIXMAN_TYPE_ABGR), which now does not require configuration.
  • The touchscreen input device is named elan-touchscreen.

Wifi

  • The wifi chip is the Broadcom 4330.
  • This device was once officially supported on Ubuntu, so it has a firmware package in the Ubuntu repositories
  • "Desktop" Linux firmware are outdated. Check here for latest one.
  • It is possible to manually get wifi working by manually copying fw_bcmdhd.bin and nvram.txt to their kernel-specified locations and configuring /etc/network/interfaces. At this point, running /etc/init.d/networking restart, gave an error about being unable to get a MAC address. After restarting the device to find that wifi Just Worked™, it was possible to successfully scan for wireless networks and establish a connection to secured wireless APs.
  • There's a proper firmware subpackage now, wifi device should work out-of-the box.

USB networking

Pending Issues

  • pmaports#201: device seems to reboot spontaneously under heavy load (could be a hardware problem though, needs more testing).
  • pmbootstrap#1422: The system partition is too small to hold rootfs images over 650Mb (e.g. Plasma Mobile is about 1.1Gb). Flashing to userdata partition fails.

See also

These are other pending issues that are related to this device:

  • pmbootstrap#60: Use the system and userdata partition on Android with LVM
  • #1199: Unfinished pull request to use "unlegacy's kernel"

Fun Fact

grouper was the first tablet to run pmOS!