ASUS MeMO Pad 7 (asus-me176c)

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ASUS MeMO Pad 7 (ME176C(X))
asus-me176cx running postmarketOS
asus-me176cx running postmarketOS
Manufacturer ASUS
Name MeMO Pad 7 (ME176C(X))
Codename asus-me176c
Released 2014
Category community
Original software Android
Original version 4.4 KitKat
Extended version 5.0 Lollipop + UEFI
postmarketOS kernel linux-edge (Alpine)
Hardware
Chipset Intel Bay Trail T Z3745
CPU Intel® Atom™ CPU Z3745 @ 1.33GHz (Quad-Core)
GPU Atom Processor Z36xxx/Z37xxx Series Graphics & Display
Display 7" 800x1280 IPS LCD
Storage 8/16 GB
Memory 1 GB
Architecture x86_64
Type tablet
Unixbench Whet/Dhry score 1664.4
Features
USB Networking
Works
Flashing
Works
Touchscreen
Works
Display
Works
WiFi
Works
FDE
Works
Mainline
Works
Battery
Works
3D Acceleration
Works
Audio
Works
Bluetooth
Works
Camera
Broken
GPS
Broken
Mobile data
Unavailable
SMS
Unavailable
Calls
Unavailable
USB OTG
Works
NFC
Unavailable
Sensors
Accelerometer
Works
Magnetometer
Works
Ambient Light
Proximity
Hall Effect
Barometer
Power Sensor
Misc
Keyboard
Touchpad
USB-A
HDMI/DP
Ir TX
Unavailable
FOSS bootloader



Contributors

Users owning this device


Installation

Preparation

The device has a locked Android bootloader. To boot other operating systems, you need to replace the bootloader entirely with a custom one.

  1. Make sure that you are running Android 5.0 (Lollipop) - older versions did not have UEFI firmware.
  2. Install me176c-boot.
  3. Set up the APD partition as additional ESP (EFI System Partition), see me176c-boot - Setting up an additional ESP partition.

Pre-built image

Download 2 files, as explained in installation#download.

  1. <date>-...-asus-me176c-bootpart.img.xz (boot partition)
  2. <date>-...-asus-me176c.img.xz (rootfs)

Unpack them using unxz *.xz.

pmbootstrap

Follow the pmbootstrap article to create your own postmarketOS image until you ran pmbootstrap install. Then use pmbootstrap export to get the same files as in the pre-built images section.

Flashing boot partition

The bootloader cannot boot directly from a SD card, therefore the boot partition must be always on internal storage.

Boot into Fastboot mode, and use fastboot flash APD asus-me176c-bootpart.img (or pmbootstrap flasher flash_kernel with pmbootstrap) to flash the boot partition. Then you need to create a boot entry for postmarketOS. Create a file pmos.conf.

For pmOS v22.12 and edge use:

title    postmarketOS
volume   80868086-8086-8086-8086-000000000007
linux    /vmlinuz-edge
initrd   /intel-ucode.img
initrd   /initramfs
# Comment this out to get more output on screen while booting
options  console=null

For pmOS v22.06 use this instead:

title    postmarketOS
volume   80868086-8086-8086-8086-000000000007
linux    /vmlinuz
initrd   /intel-ucode.img
initrd   /acpi-me176c.img
initrd   /initramfs
# Comment this out to get more output on screen while booting
options  console=null

Note: the filenames in pmos.conf must match those in asus-me176c-bootpart.img, else expect boot hang with failed to open file: or similar console messages. In that case, inspect bootpart.img directly or examine APD contents after flashing.

To install the new boot entry, boot into TWRP recovery, mount the ESP partition, and push the new configuration using ADB: adb push pmos.conf /esp/loader/entries/

Now you can choose if you would like to install the root partition (asus-me176c(-root).img) on internal storage or a SD card.

Internal Storage

Normally you should be also able to flash the rootfs using Fastboot:

  • System partition: fastboot flash system asus-me176c.img (pmbootstrap flasher flash_rootfs)
  • Data partition (larger): fastboot flash data asus-me176c.img (pmbootstrap flasher flash_rootfs --partition=data)

However, if you get an error you may need to flash it using dd via the TWRP recovery instead:

$ gzip -c ...-asus-me176c.img | adb shell "zcat | dd of=/dev/block/by-name/data bs=4m"

It looks like Fastboot can only handle small partitions on this tablet, so the error occurs whenever the image becomes too large for Fastboot to handle. Check via fastboot getvar max-download-size (see also flash_fastboot_max_size). On a 16GB device the value is ~512MiB.

Note that on first boot the resizing of the partition containing the rootfs may fail quietly (or not occur at all?). Check the resulting filesystem(s) and partition(s) with df and sudo fdisk -l. If necessary, boot to recovery, unmount the filesystem, and use resize2fs on the partition.

SD card

Write the root partition image to a partition on your SD card:

  1. Find the correct block device $ lsblk (usually /dev/mmcblkXpY but sometimes /dev/sdXY)
  2. Write the image to the partition (Warning: Existing data will be erased): dd if=asus-me176c-root.img of=/dev/mmcblkXpY bs=4M
  3. Check resulting rootfs filesize resize2fs -P /dev/mmcblkXpY and use resize2fs to make better use of the partition.

ZRAM

Since the tablet has very little RAM, some applications might hang or crash easily. This affects web browsers (e.g. Firefox) in particular. Consider enabling ZRAM to improve the situation somewhat.

Hardware details (hwtest)

Category Model Path Status Value
framebuffer i915drmfb /sys/class/graphics/fb0 Working
drm /sys/class/drm/card0-HDMI-A-1 Working Not connected
drm /sys/class/drm/card0-DSI-1 Working 800x1280
drm /sys/class/drm/card0-DP-1 Working Not connected
magnetometer i2c-AKM9911:00 /sys/bus/iio/devices/iio:device0 Working -0.1, -0.12, 0.31 gauss
accelerometer i2c-KXJ2109:00 /sys/bus/iio/devices/iio:device1 Working 0.4, -4.58, -8.6 g
input Video Bus /dev/input/event5 Working
input bytcr-rt5640 Headset /dev/input/event4 Working
input Goodix Capacitive TouchScreen /dev/input/event3 Working
input gpio-keys /dev/input/event2 Working
input gpio-keys /dev/input/event1 Working
input ASUS Lid Cover /dev/input/event0 Working

NOTE: This is not necessary anymore on edge/v22.12.

The accelerometer orientation differs from what iio-sensor-proxy expects. The following hack corrects auto-rotation. If you know the proper way to do this in a postmarketOS device package, please consider pushing a patch.

$ cat /lib/udev/hwdb.d/61-sensor-local.hwdb
# source: https://github.com/systemd/systemd/blob/master/hwdb.d/60-sensor.hwdb
sensor:modalias:acpi:KXJ2109*:dmi:*:svnASUSTeK*:pnME176C:*
  ACCEL_MOUNT_MATRIX=-1, 0, 0; 0, 1, 0; 0, 0, 1

$ cp /etc/udev/hwdb.bin ~/hwdb.bin.BAK # save a pristine backup!
$ sudo udevadm --debug hwdb --update
$ diff ~/hwdb.bin.BAK /etc/udev/hwdb.bin # they should differ now
$ monitor-sensor  # test: tilt or rotate the screen


Some users have reported being able to charge the device and connect a USB-Hub using a Micro USB OTG Y-cable like this one. It is a cable with an integrated resistor, which manages the splitting. This enables using the tablet with a keyboard, mouse, mass-storage-device,and whatever you can think of using USB. The USB protocol is USB 2.0. (The CPU also supports USB3 but the interface is sadly not exposed.)

Sofware issues

Phosh tweaks / gotchas

  • Auto-rotate landscape is inverted. Static workaround: long press on icon to portrait, orient screen as desired, then tap to landscape.
  • Unlock button is not accessible for lockscreen rewake in landscape mode with large display scales (150%, 175%). Power cycle seems to be required.
  • Auto-rotate lockscreen orientation is fixed at locking.

Tested DE

PHOSH

...WIP...

SXMO

Thanx to it's minimalistic approach SXMO works pretty well on the me176c. It requires some practice to use it so read the docs :) !

But... this does not resolve memory-hungry issues like internet browsing with firefox or chromium. You have to be kind with the hardware: 1 GB RAM can't do much UI-/visual-stuff !

As of SXMO 1.12.0 there is no device profile. Here is where the work is needed to have a user-friendly SXMO on me176c(x).

This is how the deviceprofile of the pinephone 1.2 looks like

~$ cat /usr/bin/sxmo_deviceprofile_pine64,pinephone-1.2.sh 
#!/bin/sh
# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2022 Sxmo Contributors

export SXMO_WIFI_MODULE=8723cs
export SXMO_SYS_FILES="/sys/module/$SXMO_WIFI_MODULE/parameters/rtw_scan_interval_thr /sys/power/state /sys/devices/platform/soc/1f00000.rtc/power/wakeup /sys/power/mem_sleep /dev/rtc0 /sys/devices/platform/soc/1f03400.rsb/sunxi-rsb-3a3/axp221-pek/power/wakeup"
export SXMO_TOUCHSCREEN_ID=8
export SXMO_MONITOR="DSI-1"
export SXMO_ALSA_CONTROL_NAME=PinePhone
export SXMO_SWAY_SCALE="2"

and for the Xiaomi Poco F1 (xiaomi-beryllium):

~$ cat /usr/bin/sxmo_deviceprofile_xiaomi,beryllium.sh 
#!/bin/sh
# poco f1
# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2022 Sxmo Contributors

export SXMO_DISABLE_LEDS="1"
export SXMO_MONITOR="0:0:Novatek_NT36XXX_Touchscreen"
export SXMO_POWER_BUTTON="0:0:pm8941_pwrkey"
export SXMO_VOLUME_BUTTON="1:1:gpio-keys 0:0:pm8941_resin"
export SXMO_SWAY_SCALE="2"
export SXMO_VIBRATE_DEV="/dev/input/by-path/platform-c440000.spmi-platform-c440000.spmi:pmic@3:haptics@c000-event"

All other device profiles are under the same directory /usr/bin/sxmo_deviceprofile_*.

Another very important SXMO-env_variables is:

SXMO_DEVICE_NAME=pine64,pinephone-1.2

See also