Descriptions:   This is an integrated serial input / output common-cathode display driver that connects a microprocessor with an 8-digit 7-segment digital LED display or a bar graph display or 64 independent LEDs. Which includes an on-chip B-type BCD encoder, multi-scan circuit, segment word drive, but also has 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 common microprocessors.  Each data can be addressed at the time of updating without having to rewrite all the displays.  The MAX7219 also allows the user to select or not code for each data.  The entire device contains a 150μA low power shutdown mode, analog and digital brightness control, a scan limit register allows the user to display 1-8 bits of data, and a test mode for all LEDs to emit light.  Only need 3 IO port can drive a dot matrix Dot matrix display without flicker Support cascade     Notice:  These are the parts, need to be soldered.    Module parameters:  1. A single module can drive an 8 * 8 common negative lattice;  2. Module operating voltage: 5V;  3. Module size:  5 x 3.2 x 1.5 cm (L*W*H);  4. With 4 fixed screw holes, aperture 3mm;  5. Module with input and output interfaces, 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 multiple modules are cascaded, the input of the first module is connected to the CPU, the output is connected to the input of the second module, the output of the second module is connected to the input of the third module, and so on.    Take 51 MCU as an example:  VCC → 5V;  GND → GND;  DIN → P22;  CS → P21;  CLK → P20;    Precautions:  1. VCC and GND can not be reversed, so as not to burn the chip   2. The use of 51 single-chip control of the P0 port, you must connect the pull-up resistor, the recommended resistance is 4.7K - 10K 3. Please insert the dot matrix into the round hole, then insert the round hole into the PCB board soldering. The dotted of the word side to your own, the face from left to right pin is 123456. PCB board first foot for the square pad   4. Electrolytic capacitor long pin for the positive, short pin for the negative; ceramic capacitors without positive and negative.    Package included :  1 x Dot Matrix Module