MAX7219 is an integrated serial input / output common-cathode display drivers , which connects the microprocessor 7-segment digital LED display with 8 digits , bar graph can also be connected monitor or 64 separate LED. On type B BCD encoder includes an on-chip , multi-channel scanning loop , segment word drive, but also a 8×8 static RAM for storing each data . Only one external register is used to set the segment current for each LED .
A convenient four-wire serial interface can connect all common microprocessor. Each data can be addressed in the update does not overwrite all of the display . MAX7219 also allows the user to select each of the data code or not coded . The entire device includes a 150μA low-power shutdown mode , analog and digital brightness control , a scan-limit register allows the user to 1-8 bits of data , there is an LED light so that all the detection mode .
Requires only three IO ports can drive a dot ! No flashing dot matrix display ! Support cascade !
Module Parameters:
1 single module can drive a common cathode 8 * 8 dot matrix
2 module Operating voltage : 5V
3 Module size : 5 cm X 3.2 cm wide X 1.5 cm high
4 holes with four screws , diameter 3mm, can be fixed by using our M3 studs
5 modules with input and output interfaces , support for cascading multiple modules
Wiring:
1 is a block left input port, an output port on the right .
2 When control of a single module , simply input port receiving CPU
When cascading multiple modules 3 , output and input termination CPU, the input output termination module of the first two modules of the first one , the first two modules of terminating the input of the first three modules , and so on
To 51 single example:

VCC → 5V
GND → GND
DIN → P22
CS → P21
CLK → P20