MAX7219 is an integrated serial input / output common cathode display driver . It is connected to a microprocessor and an 8 -digit 7- segment digital LED display. It can also be connected to a bar graph display or 64 independent LEDs . It includes an on-chip B -type BCD encoder, multi-channel scanning loop, segment word driver, and an 8 * 8 static RAM for storing each data. Only one external register is used to set the segment current of each LED . A convenient four-wire serial interface can be connected to all general-purpose microprocessors. Each data can be addressed without updating all displays during update. The MAX7219 also allows users to choose whether to encode or not encode each data. The entire device includes a 150A low-power shutdown mode, analog and digital brightness control, a scan limit register that allows users to display 1-8 bits of data, and a detection mode that allows all LEDs to emit light. It requires only 3 Ge IO ports to drive 1 dot matrix! No flashing during dot matrix display! Support cascading! Module parameters: 1. A single module can drive an 8 * 8 common negative dot matrix 2. Module working voltage: 5V 3. Module size: length 12.8 cm X width 3.2 cm X height 1.3 cm 4. With 64 fixing screw holes, hole diameter 3mm 5. Module with input and output interface, support multiple modules cascade Wiring instructions: 1. The left side of the module is the input port, and the right side is the output port. 2. When controlling a single module, only need to connect the input port to the CPU 3. When the plurality of cascaded modules, the first one input termination module to the CPU , the output end of the two input module, the first two output termination module of 3 input modules, and so forth . .. Take 51 microcontroller as an example: VCC 5V GND GND DIN P2.2 CS P2.1 CLK P2.0