Chuwi Hi9 Air

Chuwi Hi9 Air (Mediatek Helio X20 chipset)

Pretty complete hardware support and good stability with 8.1 (Oreo) and 9.0 (Pie) Treble GSI.

Steps to install

Baseline: Hi9 Air with Chuwi 20181122 stock ROM. Restore Chuwi stock ROM via the MTK SP Flash Windows toolkit using the Format All + Download option, in case anything goes wrong.

• enable "OEM unlock" in Android developer options

  ℹ️ type on build number seven times to unlock developer mode in Android system settings: System>About

• use factory settings reset in Android system settings

• wait for erase to finish and power off (long press)

• start device with power and vol+ simultaneously for bootloader menu, select "Fastboot Mode" via 'vol+', then confirm OK via 'vol-'

• unlock bootloader

  ℹ️ You may keep the bootloader locked, if TWRP is installed via SP Flash as well and you subsequently install the system image and OpenGApps via TWRP...

  $ fastboot oem unlock
  

  Confirm OK on screen via 'vol+'.

  ⚠️ When relocking the bootloader again via fastboot oem lock the device won't boot custom images any longer...

• flash image with the fastboot utility (after uncompressing downloaded xz archive):

  $ fastboot erase system
  $ fastboot -u flash system system-arm64-aonly-vanilla-nosu.img
  $ fastboot reboot
  

  🔁 This step may be repeated for later image releases with fixes and Android security patches (tested successfully for v31>32>123)...

  Alternatively, you could flash via TWRP as "System Image". Refrain from formatting data, as the device will fail to boot then 👎: Link

• wait patiently for another erase job to finish and initial boot (which now displays android animation instead of CHUWI) to complete: This will take several minutes

Hardware support

Component	Comment
Camera	yes (both work, front cam orientation upside down)
Speaker / Mic	yes / yes
Bluetooth	yes (works for 8.1 GSI, with 9 GSI enable the Mediatek workaround under phh treble settings > misc features > bluetooth workarounds )
WiFi	yes (but signal seems worse compared to stock ROM)
SIM / Mobile Data	partial (SIM1 only, does not reactivate after standby - reboot required)
Voice	yes
SMS	yes
VoLTE	no (MTK 6797)
Fingerprint	n/a
NFC	n/a
SD Card	yes
Casting	no, only via Google Home (as for Chuwi stock ROM)

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Tested by bofh2k - phh-treble 8.1 v32 & 9 v123 (arm64-aonly-vanilla-nosu) - 2020-02-29