1. The MAX7219 is an integrated serial input/output common cathode display driver
that connects a microprocessor to an 8-digit digital 7-segment LED display. It can also
be connected to a bar graph display or 64 separate LEDs.
2. It includes an on-chip B-type BCD encoder, multi-channel scan loop, segment word
driver, and an 8*8 static RAM to store each data. Only
one external register is used to set the segment current of each LED.
3. A convenient four-wire serial interface can be connected to all common
microprocessors. Each data can be addressed without any need to overwrite
all displays when updating. The MAX7219 also allows the user to choose
whether to encode or not encode each data.
4. The entire device includes a 150μA low-power shutdown mode, analog and digital
brightness control, a scan limit register that allows the user to display 1-8 bits of data,
and a detection mode that allows all LEDs to illuminate.
5. Only need 3 IO ports to drive 1 dot matrix! No flicker when the dot matrix is ??displayed! Support cascading!
6. Module with input and output interface, support multiple modules cascade.
7. With 64 fixing screw holes, 3mm aperture, a single module can drive an 8*8 common cathode array.

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, you 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 → P2.2
CS → P2.1
CLK → P2.0

Packing includes::
1 x dot matrix module
5 x DuPont line