Touch input for st7793. open smart 16pin

[davidarroyo1234]

First of all I wanted to thank you for your work.

I have a question.

I have a open smart 3.5 tft display with this setup.

(Screen pins-> ESP32 pins)
D0 -> 12
D1 -> 13
D2 -> 26
D3 -> 25
D4 -> 17
D5 -> 19
D6 -> 27
D7 -> 14
RD -> 2
WR -> 4
RS -> 15
CS -> 33
RESET -> 32

Which are the correct pins on each parameter for this to work? Especially the parameter adc_yp and adc_xm

[nopnop2002]

The 4-line resistor touch screen uses 4 pins.

• X(+):Digital Output
• X(-):Digital Output/Analog Input
• Y(+):Digital Output/Analog Input
• Y(-):Digital Output

ESP-IDF cannot provide both digital output and analog input at the same time using a single gpio.
Two GPIOs are required to perform digital output and analog input.
(X-) and ESP32 are connected by two wires.
(Y+) and ESP32 are connected by two wires.

(X-) ----+---- Gpio for Digital Output
         +---- Gpio for Analog Input

(Y+) ----+---- Gpio for Digital Output
         +---- Gpio for Analog Input

When reading analog with the ESP-IDF ADC, use the channel number instead of the GPIO number.

adc_yp is ADC1 channel# for reading Y+ analog value.

adc_xm is ADC1 channel# for reading X- analog value.

Refer to the ESP32 data sheet for the relationship between ADC channels and GPIOs.

---

The explanation was difficult to understand, so I updated the README.

[davidarroyo1234]

Oh so from the same lcd pin i have to connect to 2 esp32 pins? 1 for the input and 1 for the output?

[nopnop2002]

Yes
You're right.

from the same lcd pin you have to connect to 2 esp32 pins

(X-) ----+---- Gpio for Digital Output
         +---- Gpio for Analog Input

(Y+) ----+---- Gpio for Digital Output
         +---- Gpio for Analog Input

[davidarroyo1234]

Okay, thank you so much.

I will try this in the afternoon.

[nopnop2002]

These TFTs are designed for the AtMega328 (Arduino UNO).

With AtMega328 (Arduno UNO), one GPIO can be used by switching between digital output and analog input at runtime.

However, ESP-IDF cannot do this, so two GPIOs are required.

[davidarroyo1234]

Thank you :), now it's working.

Im closing the issue.