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 |
|---|---|---|---|---|
| 1 | VCC | +5V Power | 2 | 5V |
| 2 | GND | Ground | 6 | GND |
| 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 |
|---|---|---|---|---|
| 1 | VCC | +5V Power | 4 | 5V |
| 2 | GND | Ground | 14 | GND |
| 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.
