Arduino Uno + MAX7219 8x8 LED Matrix via SPI, using LedControl Library

We can add LedControl Library to Arduino IDE, to control 8*8 LED Matrix with MAX7219 via SPI. LedControl is a library for the MAX7219 and the MAX7221 Led display driver.
(ref: http://wayoda.github.io/LedControl/)

Open the File > Examples > LedControl > LCDemoMatrix

LCDemoMatrix.ino

//We always have to include the library
#include "LedControl.h"

/*
 Now we need a LedControl to work with.
 ***** These pin numbers will probably not work with your hardware *****
 pin 12 is connected to the DataIn 
 pin 11 is connected to the CLK 
 pin 10 is connected to LOAD 
 We have only a single MAX72XX.
 */
LedControl lc=LedControl(12,11,10,1);

/* we always wait a bit between updates of the display */
unsigned long delaytime=100;

void setup() {
  /*
   The MAX72XX is in power-saving mode on startup,
   we have to do a wakeup call
   */
  lc.shutdown(0,false);
  /* Set the brightness to a medium values */
  lc.setIntensity(0,8);
  /* and clear the display */
  lc.clearDisplay(0);
}

/*
 This method will display the characters for the
 word "Arduino" one after the other on the matrix. 
 (you need at least 5x7 leds to see the whole chars)
 */
void writeArduinoOnMatrix() {
  /* here is the data for the characters */
  byte a[5]={B01111110,B10001000,B10001000,B10001000,B01111110};
  byte r[5]={B00111110,B00010000,B00100000,B00100000,B00010000};
  byte d[5]={B00011100,B00100010,B00100010,B00010010,B11111110};
  byte u[5]={B00111100,B00000010,B00000010,B00000100,B00111110};
  byte i[5]={B00000000,B00100010,B10111110,B00000010,B00000000};
  byte n[5]={B00111110,B00010000,B00100000,B00100000,B00011110};
  byte o[5]={B00011100,B00100010,B00100010,B00100010,B00011100};

  /* now display them one by one with a small delay */
  lc.setRow(0,0,a[0]);
  lc.setRow(0,1,a[1]);
  lc.setRow(0,2,a[2]);
  lc.setRow(0,3,a[3]);
  lc.setRow(0,4,a[4]);
  delay(delaytime);
  lc.setRow(0,0,r[0]);
  lc.setRow(0,1,r[1]);
  lc.setRow(0,2,r[2]);
  lc.setRow(0,3,r[3]);
  lc.setRow(0,4,r[4]);
  delay(delaytime);
  lc.setRow(0,0,d[0]);
  lc.setRow(0,1,d[1]);
  lc.setRow(0,2,d[2]);
  lc.setRow(0,3,d[3]);
  lc.setRow(0,4,d[4]);
  delay(delaytime);
  lc.setRow(0,0,u[0]);
  lc.setRow(0,1,u[1]);
  lc.setRow(0,2,u[2]);
  lc.setRow(0,3,u[3]);
  lc.setRow(0,4,u[4]);
  delay(delaytime);
  lc.setRow(0,0,i[0]);
  lc.setRow(0,1,i[1]);
  lc.setRow(0,2,i[2]);
  lc.setRow(0,3,i[3]);
  lc.setRow(0,4,i[4]);
  delay(delaytime);
  lc.setRow(0,0,n[0]);
  lc.setRow(0,1,n[1]);
  lc.setRow(0,2,n[2]);
  lc.setRow(0,3,n[3]);
  lc.setRow(0,4,n[4]);
  delay(delaytime);
  lc.setRow(0,0,o[0]);
  lc.setRow(0,1,o[1]);
  lc.setRow(0,2,o[2]);
  lc.setRow(0,3,o[3]);
  lc.setRow(0,4,o[4]);
  delay(delaytime);
  lc.setRow(0,0,0);
  lc.setRow(0,1,0);
  lc.setRow(0,2,0);
  lc.setRow(0,3,0);
  lc.setRow(0,4,0);
  delay(delaytime);
}

/*
  This function lights up a some Leds in a row.
 The pattern will be repeated on every row.
 The pattern will blink along with the row-number.
 row number 4 (index==3) will blink 4 times etc.
 */
void rows() {
  for(int row=0;row<8;row++) {
    delay(delaytime);
    lc.setRow(0,row,B10100000);
    delay(delaytime);
    lc.setRow(0,row,(byte)0);
    for(int i=0;i<row;i++) {
      delay(delaytime);
      lc.setRow(0,row,B10100000);
      delay(delaytime);
      lc.setRow(0,row,(byte)0);
    }
  }
}

/*
  This function lights up a some Leds in a column.
 The pattern will be repeated on every column.
 The pattern will blink along with the column-number.
 column number 4 (index==3) will blink 4 times etc.
 */
void columns() {
  for(int col=0;col<8;col++) {
    delay(delaytime);
    lc.setColumn(0,col,B10100000);
    delay(delaytime);
    lc.setColumn(0,col,(byte)0);
    for(int i=0;i<col;i++) {
      delay(delaytime);
      lc.setColumn(0,col,B10100000);
      delay(delaytime);
      lc.setColumn(0,col,(byte)0);
    }
  }
}

/* 
 This function will light up every Led on the matrix.
 The led will blink along with the row-number.
 row number 4 (index==3) will blink 4 times etc.
 */
void single() {
  for(int row=0;row<8;row++) {
    for(int col=0;col<8;col++) {
      delay(delaytime);
      lc.setLed(0,row,col,true);
      delay(delaytime);
      for(int i=0;i<col;i++) {
        lc.setLed(0,row,col,false);
        delay(delaytime);
        lc.setLed(0,row,col,true);
        delay(delaytime);
      }
    }
  }
}

void loop() { 
  writeArduinoOnMatrix();
  rows();
  columns();
  single();
}

Connect MAX7219 8x8 LED Matrix to Arduino Uno as stated in the example:
- pin 12 is connected to the DataIn
- pin 11 is connected to the CLK
- pin 10 is connected to LOAD (it's cs marked on my sample)
- +5V to VCC
- GND to GND

Run.

Check the video:

Arduino Uno + SPI 8x8 LED Matrix, with MAX7219 LED driver

MAX7219 is a LED Driver from Maxim to drive either 64 individual Led's, or up to 8 digits of 7-segment displays. The drivers implement a SPI compatible slave interface that can be controlled from the Arduino using only 3 of the digital output pins. Know more about MAX7219, and MAX7221, refer to http://playground.arduino.cc/Main/MAX72XXHardware.

This example show how Arduino Uno work with DIY boeard of SPI 8x8 LED Matrix, with MAX7219 LED driver and 1088AS row cathode column anode 8x8 LED Matrix.


Visit http://playground.arduino.cc/LEDMatrix/Max7219, copy the sample sketch and un-comment your expected pattern to display.

//reference: http://playground.arduino.cc/LEDMatrix/Max7219

/* code for max 7219 from maxim, 
reduced and optimised for useing more then one 7219 in a row,
______________________________________

 Code History:
 --------------

The orginal code was written for the Wiring board by:
 * Nicholas Zambetti and Dave Mellis /Interaction Design Institute Ivrea /Dec 2004
 * http://www.potemkin.org/uploads/Wiring/MAX7219.txt

First modification by:
 * Marcus Hannerstig/  K3, malm� h�gskola /2006
 * http://www.xlab.se | http://arduino.berlios.de

This version is by:
 * tomek ness /FH-Potsdam / Feb 2007
 * http://design.fh-potsdam.de/ 

 * @acknowledgements: eric f. 

-----------------------------------

General notes: 


-if you are only using one max7219, then use the function maxSingle to control
 the little guy ---maxSingle(register (1-8), collum (0-255))

-if you are using more then one max7219, and they all should work the same, 
then use the function maxAll ---maxAll(register (1-8), collum (0-255))

-if you are using more than one max7219 and just want to change something
at one little guy, then use the function maxOne
---maxOne(Max you wane controll (1== the first one), register (1-8), 
collum (0-255))

/* During initiation, be sure to send every part to every max7219 and then
 upload it.
For example, if you have five max7219's, you have to send the scanLimit 5 times
before you load it-- other wise not every max7219 will get the data. the
function maxInUse  keeps track of this, just tell it how many max7219 you are
using.
*/

int dataIn = 2;
int load = 3;
int clock = 4;

int maxInUse = 4;    //change this variable to set how many MAX7219's you'll use

int e = 0;           // just a varialble

                     // define max7219 registers
byte max7219_reg_noop        = 0x00;
byte max7219_reg_digit0      = 0x01;
byte max7219_reg_digit1      = 0x02;
byte max7219_reg_digit2      = 0x03;
byte max7219_reg_digit3      = 0x04;
byte max7219_reg_digit4      = 0x05;
byte max7219_reg_digit5      = 0x06;
byte max7219_reg_digit6      = 0x07;
byte max7219_reg_digit7      = 0x08;
byte max7219_reg_decodeMode  = 0x09;
byte max7219_reg_intensity   = 0x0a;
byte max7219_reg_scanLimit   = 0x0b;
byte max7219_reg_shutdown    = 0x0c;
byte max7219_reg_displayTest = 0x0f;

void putByte(byte data) {
  byte i = 8;
  byte mask;
  while(i > 0) {
    mask = 0x01 << (i - 1);      // get bitmask
    digitalWrite( clock, LOW);   // tick
    if (data & mask){            // choose bit
      digitalWrite(dataIn, HIGH);// send 1
    }else{
      digitalWrite(dataIn, LOW); // send 0
    }
    digitalWrite(clock, HIGH);   // tock
    --i;                         // move to lesser bit
  }
}

void maxSingle( byte reg, byte col) {    
//maxSingle is the "easy"  function to use for a     //single max7219

  digitalWrite(load, LOW);       // begin     
  putByte(reg);                  // specify register
  putByte(col);//((data & 0x01) * 256) + data >> 1); // put data   
  digitalWrite(load, LOW);       // and load da shit
  digitalWrite(load,HIGH); 
}

void maxAll (byte reg, byte col) {    // initialize  all  MAX7219's in the system
  int c = 0;
  digitalWrite(load, LOW);  // begin     
  for ( c =1; c<= maxInUse; c++) {
  putByte(reg);  // specify register
  putByte(col);//((data & 0x01) * 256) + data >> 1); // put data
    }
  digitalWrite(load, LOW);
  digitalWrite(load,HIGH);
}

void maxOne(byte maxNr, byte reg, byte col) {    
//maxOne is for adressing different MAX7219's, 
//whilele having a couple of them cascaded

  int c = 0;
  digitalWrite(load, LOW);  // begin     

  for ( c = maxInUse; c > maxNr; c--) {
    putByte(0);    // means no operation
    putByte(0);    // means no operation
  }

  putByte(reg);  // specify register
  putByte(col);//((data & 0x01) * 256) + data >> 1); // put data 

  for ( c =maxNr-1; c >= 1; c--) {
    putByte(0);    // means no operation
    putByte(0);    // means no operation
  }

  digitalWrite(load, LOW); // and load da shit
  digitalWrite(load,HIGH); 
}


void setup () {


  pinMode(dataIn, OUTPUT);
  pinMode(clock,  OUTPUT);
  pinMode(load,   OUTPUT);

  //beginSerial(9600);
  digitalWrite(13, HIGH);  

//initiation of the max 7219
  maxAll(max7219_reg_scanLimit, 0x07);      
  maxAll(max7219_reg_decodeMode, 0x00);  // using an led matrix (not digits)
  maxAll(max7219_reg_shutdown, 0x01);    // not in shutdown mode
  maxAll(max7219_reg_displayTest, 0x00); // no display test
   for (e=1; e<=8; e++) {    // empty registers, turn all LEDs off 
    maxAll(e,0);
  }
  maxAll(max7219_reg_intensity, 0x0f & 0x0f);    // the first 0x0f is the value you can set
                                                  // range: 0x00 to 0x0f
}  

void loop () {


  //if you use just one MAX7219 it should look like this
  /*
   maxSingle(1,1);                       //  + - - - - - - -
   maxSingle(2,2);                       //  - + - - - - - -
   maxSingle(3,4);                       //  - - + - - - - -
   maxSingle(4,8);                       //  - - - + - - - -
   maxSingle(5,16);                      //  - - - - + - - -
   maxSingle(6,32);                      //  - - - - - + - -
   maxSingle(7,64);                      //  - - - - - - + -
   maxSingle(8,128);                     //  - - - - - - - +
  */

  //if you use more than one MAX7219, it should look like this
  
  maxAll(1,1);                       //  + - - - - - - -
  maxAll(2,3);                       //  + + - - - - - -
  maxAll(3,7);                       //  + + + - - - - -
  maxAll(4,15);                      //  + + + + - - - -
  maxAll(5,31);                      //  + + + + + - - -
  maxAll(6,63);                      //  + + + + + + - -
  maxAll(7,127);                     //  + + + + + + + -
  maxAll(8,255);                     //  + + + + + + + +
  
  //

  //if you use more then one max7219 the second one should look like this


  maxOne(2,1,1);                       //  + - - - - - - -
  maxOne(2,2,2);                       //  - + - - - - - -
  maxOne(2,3,4);                       //  - - + - - - - -
  maxOne(2,4,8);                       //  - - - + - - - -
  maxOne(2,5,16);                      //  - - - - + - - -
  maxOne(2,6,32);                      //  - - - - - + - -
  maxOne(2,7,64);                      //  - - - - - - + -
  maxOne(2,8,128);                     //  - - - - - - - +


  // 
  delay(2000);

}

For this example, connect the pins between the DIY board and Uno board.

• VCC - Uno 5V
• GND - Uno GND
• DIN - Uno 2
• CS - Uno 3
• CLK - Uno 4

Below video show soldering and assembling the DIY kit of SPI 8x8 LED Matrix board.


If you need to identify the pin 1 of the 1088AS 8x8 LED Matrix, refer to last post "How to identify pin 1 of 8x8 LED Matrix", part II.

More about Controlling a Led matrix or 7-segment displays with the MAX7219 or the MAX7221, in Arduino Playground.

Related:
- Arduino Uno + MAX7219 8x8 LED Matrix via SPI, using LedControl Library

Communication betweeen Arduinos using SPI

This example show how to communicate between two Arduino Uno using SPI. The connection is shown here:

On Master side, any data received from Serial (PC), it will be sent to slave Arduino using SPI. And data received from slave will be sent to Serial (PC).

SPIMaster.ino

#include <SPI.h>
byte dataOut;
byte dataIn;

int pinSS = 10;  //Slave Select, active LOW

void setup(){
  Serial.begin(115200);  //link to PC
  
  pinMode(pinSS, OUTPUT);
  digitalWrite(pinSS, HIGH);
  SPI.begin();
}

void loop(){
  while(Serial.available() > 0){
    dataOut = Serial.read();
    dataIn = spiWriteAndRead(dataOut);
    Serial.write(dataIn);
  }
}

byte spiWriteAndRead(byte dout){
  byte din;
  digitalWrite(pinSS, LOW);
  delay(1);
  din = SPI.transfer(dout);
  digitalWrite(pinSS, HIGH);
  return din;
}

On Slave side, any data received from SPI will be sent to Serial (PC) and echo back to master Arduino in next round of transmission.

SPISlave.ino

byte dataEcho;  //echo back input data in next round
byte dataToPC;  //send input data to PC

void setup() {
    Serial.begin(115200);  //link to PC
    
    //The Port B Data Direction Register
    DDRB  |= 0b00010000; 
   //The Port B 
    PORTB |= 0b00000100;
    
    //SPI Control Register
    SPCR  |= 0b11000000;
    //SPI status register
    SPSR  |= 0b00000000;
    
    dataEcho = 0;
    dataToPC = 0;
    
    sei();
}

void loop() {
  
  if(dataToPC != 0){
    Serial.write(dataToPC);
    dataToPC = 0;
  }

}

ISR(SPI_STC_vect){
  cli();
  
  //while SS Low
  while(!(PINB & 0b00000100)){
    SPDR = dataEcho;
    
    //wait SPI transfer complete
    while(!(SPSR & (1 << SPIF)));
    
    dataEcho = SPDR;  //send back in next round
  }
  sei();
}