Hello,

I have developed a driver for the GT911 for my custom board. It reads the x,y coordinates accurately and I am able to modify the configuration registers successfully.

The main issue I have is: when a touch goes away, the GT911 will report old x,y coordinates about 4 times before finally reporting no touch.

If I am only able to poll the GT911 every 30 ms (because the program is busy doing other things), then it will be 30 x 4 = 120 ms of lag in reporting the removal of the finger.

This becomes significant when interpreting swipes, because the coordinates always has 4 readings of the last x,y before giving a 'no touch' status.

As a test, I slowed the polling rate to 500ms. Then, the GT911 would report a touched finger for 4 * 500ms = 1.5 seconds *after* the finger was released!

Is there a configuration option I can change? Or is there some way to mitigate this?

I have developed a touch driver for a different manufacturer (ILI2117A), on otherwise the same code and hardware, and this issue did not exist.

Second issue:

The Programming Guide document I have states that the coordinate report rate is 5 - 20ms, which is configurable by writing 0x8055 (refresh rate register).

However, my timing analysis shows differently. The minimum time I must wait is about 13 ms after clearing the buffer status (0x814E). If a finger is places continuously on the screen - if I poll the GT911 as fast as possible, for about 10 - 13 ms it reports no touch before re-reporting a touch. I would expect this number should be 5 + 'N' ms (N = 0x8055 register value).

Again, I am wondering if I have a configuration issue. I have set 0x8055 to 0, but had no effect versus having it at 5.