SPI - GC9A01A LCD Screen

0. Connection

STM32	GC9A01A
3V3	VIN	5V or 3V3 power supply
GND	GND	Ground
PA5	SCL	SPI 1 SCLK
PA7	SDA	SPI 1 MOSI
PA9	RES	IC Reset N
PA8	DC	Data / Command select
PB6	CS	SPI 1 Chip Select N
PC7	BLK	Backlight enable

1. Configure STM32

In the left sidebar, select Connectivity -> SPI1.

Select Mode to "Transmit Only Master".

Select Hardware NSS Signal to "Disable".

Set SPI Mode to MODE0

Set Clock Parameters -> Prescaler to 2. The chip can run up to 40 Mbits/s.

2. Code

The code is adapted from Adafruit library

Adafruit_GC9A01A/Adafruit_GC9A01A.h at main · adafruit/Adafruit_GC9A01AGitHub

Adafruit-GFX-Library/Adafruit_SPITFT.h at master · adafruit/Adafruit-GFX-LibraryGitHub

One tricky think is the SPI_WRITE16 function. The byte order is easy to mess up.

In STM, when passing the uint16_t value to the transmit function, the lower byte in the memory address is transmitted first. However, we want to maintain the byte order, and thus we need to swap the uint16_t btyes before we invoke the transmission function.

3. Result

After connecting an RFID-RC522 SPI module, we can see that we can read the register from the sensor. The SPI signal looks like this:

https://community.st.com/s/question/0D53W00001nAhvYSAS/how-to-use-spi-nss-on-stm32g0