Display module: Touch is not reliable

[amirgon]

I'm using a TFT ILI9341 module with XPT2066 touch controller, like this one:

While the display works fine and a touch can be detected, the touch coordiates do not make sense and are not reliable.
This is not a calibration issue - a press on the same spot returns totally different results, sometimes with X and Y coordinates swapped.
In the example below I touched the same spot after each call to tft.gettouch. Every touch caused tft.gettouch to return a result, but the returned coordinates do not make sense:

>>> import display
>>> tft = display.TFT()
>>> tft.init(tft.ILI9341, width=240, height=320, miso=19, mosi=18, clk=5, cs=15, dc=33, bgr=True, hastouch=tft.TOUCH_XPT, tcs=32)
>>> tft.gettouch(raw=1,wait=50000)
(True, 0, 529)
>>> tft.gettouch(raw=1,wait=50000)
(True, 518, 8)
>>> tft.gettouch(raw=1,wait=50000)
(True, 0, 288)
>>> tft.gettouch(raw=1,wait=50000)
(True, 7, 264)
>>> tft.gettouch(raw=1,wait=50000)
(True, 0, 264)
>>> tft.gettouch(raw=1,wait=50000)
(True, 270, 32)
>>> tft.gettouch(raw=1,wait=50000)
(True, 7, 0)
>>> tft.gettouch(raw=1,wait=50000)
(True, 15, 0)
>>> tft.gettouch(raw=1,wait=50000)
(True, 264, 0)
>>> tft.gettouch(raw=1,wait=50000)
(True, 0, 17)
>>> tft.gettouch(raw=1,wait=50000)
(True, 520, 0)

To make sure this is not a hardware issue I tried this with two different modules. The result was the same.

[loboris]

I have tested with the same display couple of months ago, and the touch was quite reliable. After calibrating with tpcalib.py the demo application components/micropython/esp32/modules_examples/tft/paint.py was running without issues. I'll check if I've introduced some bug in the latest versions.

[taitix]

I have similar issue with a red ILI9341 module with XPT module. It seems this is a software issue since examples from the following arduino library works fine: https://github.com/Bodmer/TFT_eSPI

I managed to get meaningful raw (z, x, y) values by following change (orientation is messed up though...). https://github.com/taitix/MicroPython_ESP32_psRAM_LoBo/commit/d93202b1795f84f6ff5a4f681154f0e73c908419 Because this is the only touch device I own, I'm not sure if this is device specific behavior or some bug which affect all the device.

[masterofhw]

I think, there is a problem in tftpspi.c. The bits returning from xpr2046 are in big endian order, so you have to swap the bytes. I have made folling changes and it work for me:

@@ -604,8 +607,9 @@ int touch_get_data(uint8_t type) esp_err_t ret = spi_transfer_data_nodma(ts_spi, &t); if (ret != ESP_OK) return 0;

• uint16_t res = (uint16_t)(buf >> 8);
• uint16_t res = ((buf>>16)&0xff)+(buf&0xff00);
• res=(res>>3) & 0xfff;

• return res; }

[dvilelaf]

I think, there is a problem in tftpspi.c. The bits returning from xpr2046 are in big endian order, so you have to swap the bytes. I have made folling changes and it work for me:

@@ -604,8 +607,9 @@ int touch_get_data(uint8_t type) esp_err_t ret = spi_transfer_data_nodma(ts_spi, &t); if (ret != ESP_OK) return 0;

• uint16_t res = (uint16_t)(buf >> 8);

• uint16_t res = ((buf>>16)&0xff)+(buf&0xff00);

• res=(res>>3) & 0xfff;

• return res; }

Do you mean a XPT2046? How are you initializating the display and callibrating it? I'm trying your changes, but I can't seem to get any touch response.