MAX7219

A library for MAX7219/MAX7221 (LED matrix).

Wiring

Here is a wiring example with MAX7219 with 8x8 LED matrix.

Raspberry Pi Pico	MAX7219
3V3	VCC
GND	GND
GP19	DIN
GP18	CLK
GP16	CS

Install

npm install https://github.com/niklauslee/max7219

Usage

Here is an example:

const din = 19;
const clk = 18;
const cs = 16;

const {MAX7219} = require('max7219');
const max = new MAX7219(din, clk, cs);
max.setup();

// heart icon
const data = new Uint8Array([
  0b00000000,
  0b01100110,
  0b11111111,
  0b11111111,
  0b01111110,
  0b00111100,
  0b00011000,
  0b00000000,
]);

// show heart
max.write(data);

If you have multiple devices connected by daisy chaining, please note that the last device of the chain is the first device as shown in the below diagram.

         device 0     device 1             device n
         +------+     +------+             +------+
         |      |     |      |             |      | 
DATA <-- |      | <-- |      | <-- ... <-- |      | <-- DATA 
         |      |     |      |             |      | 
         +------+     +------+             +------+

So you can control the multiple devices as below.

const clk = 18;
const cs = 16;
const devices = 4;

const {MAX7219} = require('max7219');
const max = new MAX7219(din, clk, cs, devices);

const data = new Uint8Array([
//  device-0    device-1    device-2    device-3
//   (heart)     (smile)         (A)         (X)
  0b00000000, 0b00000000, 0b00000000, 0b00000000, // row1
  0b01100110, 0b00000000, 0b00011000, 0b01000010, // row2
  0b11111111, 0b00100100, 0b00100100, 0b00100100, // row3
  0b11111111, 0b00000000, 0b01000010, 0b00011000, // row4
  0b01111110, 0b01000010, 0b01111110, 0b00011000, // row5
  0b00111100, 0b00111100, 0b01000010, 0b00100100, // row6
  0b00011000, 0b00000000, 0b01000010, 0b01000010, // row7
  0b00000000, 0b00000000, 0b00000000, 0b00000000  // row8
]);

max.setup();
max.write(data);

API

Class: MAX7219

new MAX7219(din, clk, cs[, devices])

• din <number> The pin number for DIN.
• clk <number> The pin number for CLK.
• cs <number> The pin number for CS.
• devices <number> The number of devices connected by chaining. Default: 1.

setup()

Initialize the device.

write(data)

• data <Uint8Array> Data to be sent.

Send the data to the device. The length of data should be 8 * this.devices. For example, if you have only one 8x8 LED matrix, the data length should be 8. If you have 4 devices, data should have 32 elements. The elements should be ordered as below:

• data[0] : row 1 of device 0.
• data[1] : row 2 of device 0.
• ...
• data[7] : row 8 of device 0.
• data[8] : row 1 of device 1.
• data[9] : row 2 of device 1.
• ...
• data[15] : row 8 of device 1.
• data[16] : row 1 of device 2.
• data[17] : row 2 of device 2.
• ...

clear()

Clear the device. Set all LEDs to off.

on()

Turn on the device.

off()

Turn off the device.

setScanLimit(limit)

• limit <number>

Set the scan limit (0 ~ 7). Default is 7.

setIntensity(intensity)

• intensity <number>

Set the brightness of the LEDs (0 ~ 15).

setTestMode(mode)

• mode <boolean>

Set the test mode. Turn on all LEDs if true, otherwise turn off all LEDs.