UART peripherals on Android Things for Raspberry Pi 3

Question

How do I use UART peripherals on Android Things for Raspberry Pi 3?

It seems that by default it is assigned the linux console.

Answer 1

By default the UART port is mapped to the linux console, in order to prevent the kernel message from messing around with your peripheral.

You can disable the console by mounting the boot partition from the sdcard on your host computer using:

mount /dev/sdX1 /mnt/disk

where sdX is replaced with your sdcard reader device name (running dmesg after inserting your sdcard into your reader should help you figure out the device name).

Then edit /mnt/disk/cmdline.txt to replace the following kernel boot argument:

console=serial0,115200

with:

console=tty0

If you need to re-enable the console later for debugging purpose, just add the same argument back.

See the developer docs for more info on disabling the console.

Answer 2

Beginning with Developer Preview 3, in which USB-Serial devices support added, external USB-UART dongles like this can be used instead of built-in UART of Raspberry Pi 3.