MHS4001

6 GPIOs are required to drive the SPI display. One additional GPIO is needed for the XPT2046 touch sensor. Including the Vcc and Gnd pins, a total of 12 connections need to be made to the MCU:

Pin Configuration

Pin	Function	ESP32 Pin	Config Name	Display Pin
1	Module Power 3.3V	3.3V		3.3V
2	Module Power 5v	5V		5V
3	Not connected			NC
4	LED Backlight PWM 5V		TFT_BCKL	5V
5-10	Not connected			NC
11	Touch Interrupt	NC		TP_IRQ
12-13	Not connected			NC
14	Module Ground	GND		GND
15-16	Not connected			NC
17	Module Power	3.3V		3.3V
18	Data Command control pin	GPIO4	TFT_DC	LCD_RS
19	SPI Master Out Slave In	GPIO23	TFT_MOSI	LCD/SI/TP_SI
20	Not connected			NC
21	Touch Panel Slave Out	GPIO19	TFT_MISO	TP_SO
22	LCD Reset pin	GPIO32	TFT_RST	RST
23	SPI Clock	GPIO18	TFT_SCLK	LCD_SCK/TP_SCK
24	Chip select control pin	GPIO15	TFT_CS	LCD_CS
25	Module Ground	GND		GND
26	Touch Chip Select	GPIO22	TOUCH_CS	TP_CS

By default, pin 4 is normally connected to 5V. This turns the display backlight LED on all time. In order to control the backlight you can drive pin 4 of the display using a PNP transistor. The electronics circuit needed is not part of this diagram.

SPI MISO, MOSI and SCLK are shared between the touch controller and the LCD controller.

LCD Configuration

The lcd_config.ini file specifies the different properties of the display, except for the actual pin configuration:

raspberrypi =
    -D RPI_DISPLAY_TYPE=1
    -D ST7796_DRIVER=1
    -D TFT_WIDTH=320
    -D TFT_HEIGHT=480
    -D TFT_ROTATION=0 ; 0=0, 1=90, 2=180 or 3=270 degree
    -D SPI_FREQUENCY=80000000
    -D SPI_TOUCH_FREQUENCY=2500000
    -D USER_SETUP_LOADED=1
    -D TOUCH_DRIVER=2046 ; XPT2046 Resistive touch panel driver
    -D SUPPORT_TRANSACTIONS

HASP build_flags

Specify the LCD Configuration to use and define the 7 GPIOs in the environment build flags:

build_flags =
    ${flags.esp32_flags}
; -- TFT_eSPI build options ------------------------
    ${lcd.raspberrypi}
    ${esp32.vspi}        ; Use VSPI hardware SPI bus
    -D TFT_CS=15
    -D TFT_DC=4
    -D TFT_RST=32
    -D TFT_BCKL=-1       ; None
    -D TOUCH_CS=22

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Last update: 2022-06-04