MAX7219 is an integrated serial input / output common-cathode display driver, it connects the microprocessor 7-segment digital LED display with 8 digits, you can also connect a bar graph display or 64 independent LED. Thereon including a B-type BCD encoder chip, multi-channel scanning loop segment word driver, but also a static RAM 8 * 8 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 microprocessor. Each data can be addressed in the update do not need to rewrite all of the display. MAX7219 also allows each user to select a data coding or non-coding.
The entire device contains a 150μA low-power shutdown mode, analog and digital brightness control, a scan-limit register allows the user to display data bits 1-8, and one for all LED luminescence detection mode.
It requires only three IO ports to drive a dot matrix! No flicker when the dot matrix display! Support cascading!
Overview
The MAX7219 8×8 Dot Matrix Display Module is a cluster of four 32mm (1.25-inch) 64-LED dot matrix displays each with a built-in MAX7219 serial LED driver, internally connected to each other. Modules are available with either Red or Blue LEDs.

The MAX7219 driver chip is a flexible 7-segment, bar graph, and dot matrix LED driver that supports many functions for controlling LED displays. The driver provides flexible individual LED control and essential functions such as turning the display on or off and adjusting the LED brightness.

The display cluster requires only three IO ports to drive a dot-matrix without any flicker. The MAX7219 communicates by a 3-wire SPI bus.

Arduino libraries, such as “LedControl.h” or “MD_MAX72xx” are commonly available and supported for the Arduino IDE, making communicating with the display very straightforward.