This peripheral is an 8x8 LED matrix. It is great for retro-style UI, but obviously it is also very limited.
The names on the pins are slightly different than the ones on the board, so let's look at the connection diagram:
Ground and Vcc are the same as always.
DIN stands for data input, and therefore it is connected to the pin that transmits data from the master to the slave: MOSI (Master Out, Slave In).
SCL stands for shared clock, and CLK stands just for clock. The different naming can be confusing, but both are commonly used, so just be aware of them being the same.
Finally, we have CS (chip select). This is the pin that is ...
