In automotive environment we have an external resistive touch screen with unusual (through the CAN bus) data protocol. We’re putting a MCU to process the CAN frames and convert them into something standard. There are 3 options as we can see.
- Connect the MCU as HID touch screen to 410c’s USB.
- Connect the MCU as serial touch (just send the touch data through UART lines to 410c)
- The last solution would be to use the event interface and generate touch events… Something like listen UART port and inject the data into event0 pipe.
Technically there is another option, our MCU can be configured as i2c slave device so, theoretically we could emulate Synaptics touch screen data. But we would prefer explore the simple solutions first.
We tried the first solution. It works but when touching the screen a mouse pointer appears for a short period the disappears. Tried different HID descriptors and still having the same issue, mouse pointer or finger circle still always present for 1 sec at least. It looks like all descriptors are based on same digitizer approach with tip/finger operation.
Unfortunately we don’t have any “true” USB touch screen that works out of box with 410c board so we can get the right descriptor. If anyone has the descriptor which works properly please don’t hesitate to share it
Now we’re trying the second approach, using the serial data. Do you know what would be the “standard” serial data format supported by 410c and how to enable the corresponding driver?