This is the 4-wire resistive touch screen firmware for Arduino modified for ESP32 type UNO boards. Modification added to allow the 4-wire resistive touchscreen of MCU Friend LCDs with parallel data interfaces to be used with ESP32 UNO style boards whilst WiFi is enabled. Tested on a red board MCU Friend with default touchscreen wiring.
Although not up to data with the lastest Adafruit TouchScreen library it is still valid for ESP32 devices.
ESP32 WiFi removes access to ADC2 channel so pins 4 and 15 attached to the touchscreen no longer have analog input capability. Pin 15 already shares a connection with analog pin 35, so an additional connection is made between pin 4 and analog pin 39. Pins 35 and 39 now provide the analog input. Pins 35 and 39 are input only so always present a high impedance to avoid the risk of two outputs shorting.
An extra wiring mod is needed in addition to those shown in the TFT_eSPI instructions, but do not affect the software functionality or configuration.
Wiring for ESP UNO type board, with extra wire shown in green:
Download and install the library using your IDE, eg Arduino. The modification uses conditional compilation. To enable the changes, modify TouchScreen.h to uncomment #define ESP32_WIFI_TOUCH
// ESP32 specific
#define ESP32_WIFI_TOUCH // uncomment to use parallel MCU Friend LCD touchscreen with ESP32 UNO Wifi
#ifdef CONFIG_IDF_TARGET_ESP32S3 // for ESP32S3 Uno
#define ADC_MAX 4095 // maximum value for ESP32 ADC (default 11db, 12 bits)
#define aXM 7 // analog input pin connected to LCD_RS
#define aYP 1 // analog input pin connected to LCD_WR
#elif defined(ESP32)
#define ADC_MAX 4095 // maximum value for ESP32 ADC (default 11db, 12 bits)
#define aXM 35 // analog input pin connected to LCD_RS
#define aYP 39 // analog input pin connected to LCD_WR
#else
#define ADC_MAX 1023 // Arduino
#endif
#define NOISE_LEVEL 4 // Allow small amount of measurement noise
No changes are required to existing sketches, just recompilation.
Compatible with both TFT_eSPI and MCUFRIEND_kbv libraries
Touchscreen needs to be calibrated before use, either manually using included ESP32testTouch or eg TouchScreen_Calibr_native
