ESP32 switching I2S parallel to/from GPIO mode

[mcbp223]

Hi, when trying to make the reading from display memory work, I wasn't able to until I've supplemented the mode switching functions beginRead and endRead with reconfiguration for each data pin, in addition to the RS signal, like

for (size_t i = 0; i < 8; ++i)
{
    gpio_set_direction((gpio_num_t)pins[i], GPIO_MODE_INPUT);
    gpio_matrix_in(pins[i], 0x100, 0);
}

and

for (size_t i = 0; i < 8; ++i)
{
  gpio_set_direction((gpio_num_t)pins[i], GPIO_MODE_OUTPUT);
  gpio_matrix_out(pins[i], idx_base + i, 0, 0);
}

respectively.

Has anyone encountered this, or it could be that my chip revision is old?

[tobozo]

gpio direction is already set to both output and input, does it also improve when using GPIO_MODE_INPUT_OUTPUT both in beginRead and endRead?

[mcbp223]

That's how I tried it first, with the library unchanged, data pins set to GPIO_MODE_INPUT_OUTPUT as you have indicated. With the test_readpixel sketch I could see that there was something moving, but I don't know how to say it, it's kind of black on black, very faint, which really gave the impression of two outputs competing with each other on the same bus, so trying to set the MCU side explicitly to input only was the next step. If other ESP32 chips don't exhibit this behavior then it could be something different with mine, maybe I'll try to wire a newer revision chip to this LCD and see if it still needs the bus input only or not, since the one I am using is maybe old, ESP32-D0WDQ6 Rev 1.

With the additions I've made, if in beginRead I replace GPIO_MODE_INPUT with GPIO_MODE_INPUT_OUTPUT it goes back to not working.

[mcbp223]

I've tried with an ESP32-D0WDQ5 Rev 3, but it still needs the data bus set to input only for reading.

Could this be due to my choice of wiring? I have D0:D7=12:19, RST=25, CS=26, RD=27, RS=32, WR=33, with mcufriend style resistive touch connections at Ym=D7=19, Yp=WR=33 and Xp=D6=18, Xm=RS=32.