MAX7219 Dot Matrix Module 4 in one for Arduino

1. The left side of the module to the input port, the right to an output port.
2. When the control of a single module, simply input port connected to CPU
3. When a plurality of cascaded modules, input and output termination CPU, an input terminal of the second output end of the first module a module, the first two modules of the input terminal of the three termination modules, and so on. ..
51 microcontrollers, for example:
VCC → 5V
GND → GND
DIN → P2.2
CS → P2.1
CLK → P2.0