Product description MAX7219 is a kind of integrated serial input / output common cathode display driver, it connects the microprocessor with 8 digit 7 digit LED display, also can connect the line chart display or 64 independent LED. It includes an on-chip BCD B encoder, a multi scan circuit, a segment word driver, and there is a 8*8 static RAM used to store each data. Only one external register is used to set the segment current for each LED. A convenient four wire serial interface can be connected to all general-purpose microprocessor. Each data can be addressed in the update without rewriting all the display. MAX7219 also allows the user to select a data for each code or not.The entire device contains a 150 A low power off mode, analog and digital brightness control, a scan limit register allows the user to display the 1-8 bit data, as there is a detection mode for all LED luminescence. Only need 3 IO port can drive 1 dot matrix!Dot matrix display no flicker! Support cascade! Module parameters: 1 single module can drive a 8*8 common cathode dot matrix 2 module working voltage: 5V 3 module size: 5 cm long X width 3.2 cm X high 1.5 cm 4 with 4 fixed screw holes with diameter of 3mm and can be used to store M3 pillars fixed 5 module with input and output interface, support for multiple modules cascade Connection description: 1 the left side of the module is the input port, and the right is the output port. 2 control of a single module, the input port only need to receive CPU More than 3 modules cascaded, first modules are connected with the input end of the CPU, the output end is connected with the input end of the second modules, second modules output terminal third module input, and so on... Taking 51 single chip microcomputer as an example: VCC - 5V GND - GND DIN - P22 CS - P21 CLK - P20