MAX7219 4-in-1 dot matrix (32x8): specs and pinout
A 32 x 8 red LED dot-matrix display module; sold as a 4-in-1 module; modules of this type usually chain four MAX7219 serial LED drivers, but chaining is not documented for this module. The MAX7219 sheet from Maxim (now Analog Devices) describes the chip; the module board itself is not documented.
Specs
| Spec | Value | Source |
|---|---|---|
| Chip function | Serial LED display driver for up to 8 digits of 7-segment, bar graphs or 64 individual LEDs, with an 8 x 8 on-chip RAM; common-cathode displays | source General Description (page 1) |
| Operating supply voltage | V+ 4.0 V to 5.5 V (absolute maximum 6 V) | source Electrical Characteristics, Absolute Maximum Ratings (pages 2-3) |
| Logic input levels | VIH 3.5 V minimum, VIL 0.8 V maximum, at V+ = 5 V | source Electrical Characteristics, Logic Inputs (page 3) |
| Serial interface | 3 inputs (DIN, CLK, LOAD) with 16-bit packets, up to 10 MHz clock; DOUT passes data on for daisy-chaining | source Features (page 1); Pin Description (page 5) |
| Segment current | Set by one external resistor (RSET) on ISET; 40 mA typical segment source current with RSET = 9.53 kohm | source Electrical Characteristics (page 2); Pin Description (page 5) |
| Supply current | 8 mA maximum with RSET open; 330 mA typical with all segments on at 40 mA per segment (one chip) | source Electrical Characteristics (page 2) |
| Shutdown supply current | 150 uA maximum; data is retained | source Features and Electrical Characteristics (pages 1-2) |
| Operating temperature | 0 to +70 C (C grade) or -40 to +85 C (E grade); the grade fitted to the module is not stated | source Absolute Maximum Ratings (page 2) |
Power
| Value | Source | |
|---|---|---|
| Supply | Chip: V+ 4.0 V to 5.5 V (5 V typical application) | source Electrical Characteristics (page 2) |
| Current | Chip: up to 330 mA with all segments on at 40 mA each; module current not documented | source Electrical Characteristics (page 2) |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
These rows are the MAX7219 chip's serial and supply pins. How many chips the module carries and whether they are chained, its header pin names and order, its RSET value and its matrix parts are not covered by an official document.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| DIN (pin 1) | Serial data input, loaded into the 16-bit shift register on CLK rising edge | 5 V logic (VIH 3.5 V) | MAX7219 chip pin number | source Pin Description (page 5) |
| CLK (pin 13) | Serial clock input, 10 MHz maximum | MAX7219 chip pin number | source Pin Description (page 5) | |
| LOAD (pin 12) | Load-data input: the last 16 bits are latched on the rising edge | MAX7219 chip pin number | source Pin Description (page 5) | |
| DOUT (pin 24) | Serial data output for daisy-chaining; valid 16.5 clock cycles after DIN | MAX7219 chip pin number | source Pin Description (page 5) | |
| V+ (pin 19) | Positive supply voltage | 4.0 V to 5.5 V | MAX7219 chip pin number | source Pin Description (page 5) |
| GND (pins 4, 9) | Ground; both pins must be connected | MAX7219 chip pin number | source Pin Description (page 5) | |
| ISET (pin 18) | Connects to V+ through RSET to set the peak segment current | MAX7219 chip pin number | source Pin Description (page 5) |
Build with it
Project ideas for the MAX7219 4-in-1 dot matrix (32x8). Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Scrolling temperature ticker: The Uno gives 5 V logic and 5 V supply, inside the chip's 4.0 V to 5.5 V range and above its 3.5 V input threshold. Set the intensity low and measure the current before using a larger supply.
- Matrix clock: The DS3231 keeps time over I2C and the Nano drives the module with three signal lines (DIN, CLK, LOAD). Keep the brightness register low, since the sheet gives up to 330 mA per driver chip with all segments on.
- Score board with buttons: Each button adds one point to a counter drawn on the matrix. Use the Uno's internal pull-ups and 5 V logic.
- Sound level display: The microphone amplifier's analog output feeds an Uno analog input and the level is drawn as bars across the 32 columns. Power both from the Uno's 5 V pin with the matrix intensity kept low. Set the intensity register low in setup() before the first display call.
Common mistakes
- Driving the inputs from 3.3 V logic: the chip needs at least 3.5 V to read a high at V+ = 5 V, so use a 5 V board such as an Arduino Uno, or add a level shifter, unless the module board is documented to cope with 3.3 V (source: link, Electrical Characteristics p.3)
- Running all LEDs at full intensity from a USB port: the sheet gives 330 mA typical per chip with every segment on at 40 mA, and each driver on the module can draw that, so keep the intensity register low and use a supply sized for the measured draw (source: link, Electrical Characteristics p.2)
- Supplying more than 5.5 V: operating range is 4.0 V to 5.5 V and the absolute maximum is 6 V, so do not power the module from a 9 V pin (source: link, Electrical Characteristics p.2 and Absolute Maximum Ratings)
Not covered by the official source
- The module board (header order, RSET value, number of chips and the matrix part) is not covered by an official document; the chip sheet says nothing about the 8 x 8 matrix blocks.
- The temperature grade of the chip on the module is not stated.
- Chaining of the four blocks on this module is not documented here; the 4-in-1 name is the only indication.
Sources
- link (Maxim MAX7219/MAX7221 data sheet 19-4452 Rev 4 7/03; copy hosted on a mirror)