HYNITRON CST816S

Zephyr has evolved and now there is something that serve as a touchscreen device. (KSCAN_TOUCH)

the board definition file has been adapted slightly, using the focaltech ft5336 as a touch_controller. A minor change in this driver is enough to get data from the hynitron cst816S.

The big advantage : almost standard zephyr install! Unfortunately I cannot get the KSCAN_TOUCH working in an out-of-tree setup.

I have created the renamed ft9999 driver.

west build -p -b pinetime_devkit0 samples/display/lvgl

this driver does not exist, so it has been created. Still work in progress ….

Overview

(this is the old way of doing things ….)

the Hynitron cst816s is a touchscreen. Zephyr doesn’t handle touchscreens yet. In order to investigate, the touchscreen driver has been created as a sensor. In fact it senses your finger ;)

Requirements

for this sensor does not exist any driver, so here’s what I did to create one under zephyr

adapt CMakeLists.txt adapt Kconfig add yaml file

create driver

The driver reads only one position. Multitouch is possible, but the screen is small….

see under drivers/sensor/cst816s

have a look at the pinetime.dts (under board/arm/pinetime) file:

&i2c1 {
        cst816s@15 {
                   compatible = "hynitron,cst816s";
                   reg = <0x15>;
                   label = "CST816S";
                   };
       };

Building and Running

There are two samples :

• samples/gui/lvtouch (graphical)

• samples/sensor/cst816s (no graphics)

Todo

The graphical sample doesn’t handle interrupts.

References

There is little available for this touchscreen.