(35) ESP32 and the circular GCA901 240*240 pixel TFT display

by Floris Wouterlood – June 13, 2023

Summary
This post concerns the wiring of a circular 1.28” diagonal 240*240 pixel color display with GCA901A controller to an ESP32 microcontroller. Because the circular display arrived on a five-pin SPI breakout board the ESP32 has a wealth of pins available for all kinds of purposes other than driving displays. This inspired me to construct a bench type of device equipped with an ESP32, a circular display and a row of pin sockets.

figure 1. Wiring diagram: ESP32-WROOM-32 board, 1.28” circular 240*240 SPI GC9A01 TFT display.

Pin mapping
This TFT display breakout board has seven pins (figure 1) of which five serve the SPI interface (CS, DC, SDA, SCL and RST). The two remaining pins are marked VCC and GND. These two are obvious. Note that the display at hand is a 3.3V item. The RST pin is not connected.

Components of the bench

• 1x soldering prototyping board, 8×6 cm, 31×26 holes, double-sided
• 1x ESP32-WROOM-32 microcontroller board, 38-pins
• 1x CG9A01 1,28 inch diameter circular TFT display, 5-pin SPI+VCC+GND
• 2x 19-pin socket header (to accommodate an 38-pin ESP32
• 1×7 pin socket to accomodatev the display
• 1x 4-pin and 1×17 pin socket header for bench purposes
• 2x 4-pin pin headers for bench purposes (3V3, GND)
• Audio cassette box
• wire
• 3x nylon spacer with screw and nut to fasten the board onto the cassette box.

Pin connectivity table

Wiring
We are using conventional pin mapping: SCL (clock) and SDA (data, on other displays named MOSI) connect to pins D18 and D23 of the ESP32, respectively. Wiring is as follows (figs. 2,3).

figure 2. Pin connectivity ESP32-WROOM-32 board, 1.28” circular 240*240 SPI GC9A01 TFT display.

Building a bench
The ESP32 comes with an impressive set of pins. A wired, soldered device equipped with a pin socket that connects to the free pins of the ESP32 creates an attractive bench. In my design a vertical strip on the left of the ESP32 / display carries a pin socket plus at its base one four-pin GND socket and a four-pin 3V header. All pins to supply external sensors with power and data communication are now on the front of the bench device, easily available for experimentation (figures 3,4). The sockets are stickered with their respective ESP pin connections.

figure 3. Outlay and wiring scheme for the ESP32 / circular display bench. The wiring between the extra pin sockets and the free ESP32 pins is not included.

Downloadable sketch

• WROOM32_GC9A01-Adafruit_GFX.ino – needs the Adafruit_GFX.h and the Adafruit_GC9A01A.h libraries
• WROOM32_GC9A01_TFT_eSPI.ino – needs Bodmer’s <TFT_eSPI.h> library and a user setup file that ontains settings that directs the compiler to do its job properly with this combination of ESP31 and display.

The ZIP file: WROOM32_GC9A01.zip contains the following

TFT_eSPI User_Setup_Select file
Download the library <TFT_eSPI.h>. After installation you will see in your snap-arduino-libraries folder a main folder named TFT_eSPI. That folder hosts a subdirectory named User_Setups. The file below is an adaptation of setup file #46 in that subdirectory.
My setup file carries the name <Setup_ID_46_ESP32_GC9A01.h>
A line should be added in User_Setup_Select.h, and uncommented:

#include <User_Setups/ Setup_ID_46_ESP32_GC9A01.h> // your comment

Content of User_Setups/ Setup_ID_46_ESP32_GC9A01.h is the followig:

// See SetupX_Template.h for all options available
#define USER_SETUP_ID 46_ESP32_GC9A01

#define GC9A01_DRIVER

#define TFT_MISO 19
#define TFT_MOSI 23
#define TFT_SCLK 18
#define TFT_CS 4 // Chip select control pin
#define TFT_DC 2 // Data Command control pin
#define TFT_RST 4 // Reset pin (could connect to RST pin)
//#define TFT_RST -1 // Set TFT_RST to -1 if display RESET is connected to ESP32 board RST

#define LOAD_GLCD
#define LOAD_FONT2
#define LOAD_FONT4
#define LOAD_FONT6
#define LOAD_FONT7
#define LOAD_FONT8
#define LOAD_GFXFF
#define SMOOTH_FONT

#define SPI_FREQUENCY 40000000
#define SPI_READ_FREQUENCY 20000000
#define SPI_TOUCH_FREQUENCY 2500000

figure 4. The completed bench built around an ESP32 and a GC9A01 circular display. The microcontroller is running the graphics test attached to the AdafruitGC9A01 library.