If the touch input seems to not work at all, it may be that your unit is part of an older batch that used a different display.

To fix the touch input issue, you will need to set an environment variable for the bootloader.

There are two ways to do that:

1. Via the Console

Connect to the device via SSH or via the debug serial port as explained in Device connection.

Once connected and logged in as root, run:

fw_setenv fit_image_config config_tianma

Reboot the device. To make sure the environment variable persisted the reboot, connect again to the device and run

fw_printenv fit_image_config

It should output: fit_image_config=config_tianma

2. Via the uboot prompt

Note: This will only work while connected via the debug serial port because you need to send input to the device before the operating system is loaded.

Steps:

1. Power off the device
2. Connect to the serial debug port
3. On the host computer start the serial connection.
See the instructions at Connecting via Serial Port to find the right command
4. Repeatedly press any key and power on the device at the same time
This is a similar process to booting into the BIOS for regular PCs.
You should be shown the uboot prompt:

5. Run:

setenv fit_image_config config_tianma 
saveenv
boot

The device tree overlay for the Tianma display should now be loaded.

3. Software updates

For software updates, if a file named fdt_overlay is present in the root directory of the USB stick, the post-install script will automatically apply the device tree overlay.

To enable this feature, simply create an empty file named fdt_overlay in the root of the USB stick, alongside the .swu file you intend to use for the update.