Touch Input Display Driver for Android Things

Android Things and touch input displays

For the Raspberry Pi 3 the Android Things platform so far only supports the official RPi screen to be used with the touch input. The cheaper screens (mostly Chinese) are not supported for touch input. That's the reason for creating this library. Initially I had only two screens: A 3.5" Kedei and a 5" Waveshare screen. Both are using the XPT2046 touch controller.

Supported Displays

Out of the box the following displays are supported, however the system is free and open to add your own driver:

• Kedei HDMI (Tested with a 3.5")
• Waveshare HDMI (Tested with a 5")

Usage

Prerequisites

Before using the driver you need to make sure you have the Input Device Confguration file (.idc) installed on your Android things device. To do so mount the SD card of your Android Things device and in the root partition under /system/usr/idc/ you should copy the AndroidTouchInputDriver.idc file that is available in the root of this project. If you do not copy that file the driver will work but Android will think that the driver is a physical mouse, which obviously results in totally different behaviour.

Gradle

compile 'eu.vranckaert.driver:touch:1.1.0'

Default drivers

You can use the library in two different ways:

1. Using the TouchScreenDriverApplication Add an Application to your source code and reference it from the AndroidManifest. Then extend your application from the TouchScreenDriverApplication and override the getDriverProfile() method. The DriverProfile can be initiated using WaveshareProfile.getInstance(WaveshareProfile.DIMENSION_800_480); or KedeiProfile.getInstance(KedeiProfile.DIMENSION_480_320);. This will make sure the correct driver for your display configuration/dimensions will be loaded.

2. Implementing the TouchScreenDriverManager yourself If you cannot extend your Application from the TouchScreenDriverApplication then you can use the TouchScreenDriverManager to load and unload the driver in the onCreate and onDestroy methods of your Application instance. The manager is a singleton class that manages any state for you. Using this method you will also have to impelement a callback that provides DriverProfile for your screen.

Custom Drivers

Adding a custom driver is really simple. The hardest part in a custom driver is knowing how to read from your touch input display.

To implement the driver in the library you should extend the eu.vranckaert.driver.touch.driver.Driver class or the eu.vranckaert.driver.touch.driver.SpiDriver class in case your touch input display is SPI compatible. If your touch input display uses the XPT2046 touch controller you can even directly extend the eu.vranckaert.driver.touch.driver.XPT2046Driver class. It's the driver class that will contain the reading/writing logic for your touch display.

Next you need a eu.vranckaert.driver.touch.profile.DriverProfile which needs a Vendor (or Vendor.UNKNOWN in case your vendor is not yet listed), and a ScreenDimension specifying the width, height and screen ratio. The Ratio is an enum with fixed ratio values, or again a Ratio.UNKNOWN if the ratio is not yet listed.

Demo

There's a demo module to test your drivers immediately. The demo contains a splash screen, some default Android controls ideally to test touch inputs (a slider, a switch and buttons) and a 'Touch Debugging' mode, when enabled drives a circle on the touch position that you discover from the display. This way you can almost perfect calibrate the driver against the specific display!

Contributing

I would like to see new drivers added to this library. So please let me know or please contribute to the code base to get your dirver added!