I have a MAX7219 dot matrix module (this one) that I'm trying to run on my Raspberry Pi 4 with the Luma.LED library. Its documentation suggests the following GPIOs/pins be used:
|Board Pin||Name||Remarks||RPi Pin||RPi Function|
|3||DIN||Data In||19||GPIO 10 (MOSI)|
|4||CS||Chip Select||24||GPIO 8 (SPI CE0)|
|5||CLK||Clock||23||GPIO 11 (SPI CLK)|
However, mine is connected as follows, because I'm also running an epaper on the Raspberry Pi that needs some of the pins:
|Board Pin||Name||Remarks||RPi Pin||RPi Functions|
|3||DIN||Data In||38||GPIO 20 (DIN/MOSI6/MOSI1/GPCLK0)|
|4||CS||Chip Select||12||GPIO 18 (CLK/CE0N6/CE0N1/PWM0)|
|5||CLK||Clock||40||GPIO 21 (SCLK6/SCLK1/GPCLK1)|
I had the dot matrix module working in this configuration before but after a reinstall, I can't get it to work anymore. I have a vague memory I needed to change a config file somewhere to make the module work with the different pin, but cannot remember which one or how. Possibly something in /boot/config.txt?
What I've tried:
- Made sure SPI is enabled via sudo raspi-config > 3-Interface options > I4-SPI.