Technical summary
The module uses a 3-wire serial bus: a CS wire that selects the MAX7219 and latches the data into the chip (stores it), a CLK wire that clocks the sending of the signals, and finally a DIN wire that receives the data + 2 wires for its power supply.
It can be used to build electronic display panels, and you can make your applications livelier thanks to the LED brightness adjustment that can be implemented in software.
