LED Matrix Arduino Shield

Abstract

After getting a couple of flashing lights working on a microprocessor, the next fun project is generally building some kind of Matrix.  At first I built a 5×5 LED matrix which was relatively simple to solder together.  When trying to make one much larger, the task because significantly more complex.  That’s when I decided to build a LED Matrix Shield for the Arduino which did not use Charliplexing, like the LoL shield.  I wanted something that was simpler to understand and (ultimately) code for.  Unfortunately, 5mm LEDs means 8 columns x 6 rows, instead of the traditional 8×8.

Electronics

• (1) – 8×6 LED Matrix LED PCB
• (48) – Bright blue 5mm LEDs
• (6) – SMT 1206 150Ω resistors
• Header Pins
  • Optionally, for power and analog inputs, only 8 header pins necessary.
• (1) – SMT 1206 LED [optional]
• (1) – SMT 1206 150Ω  resistor [optional]
• (1) – SMT push button [optional]
• Sunglasses [optional]

Schematic

The actual code used to demonstrate the shield in the attached YouTube videos has been lost.  Below is an early example of the code, which used hard coded letters.

#define numOfColumns 8
#define numOfRows 6
#define matrixSize 48
#define bigWait 500 // milliseconds
#define povWait 250 // microseconds
#define animationWait 100 // milliseconds
#define frames 10

int columnPins[numOfColumns] = {2,3,4,5,6,7,8,9};
//int sourcePins[numOfColumns] = {2,3,4,5,6,7,8,9};
int rowPins[numOfRows] = {10,11,12,A0,A1,A2};
//int sinkPins[numOfSinks] = {10,11,12,A0,A1,A2};
unsigned int rowStates[6] = {0,0,0,0,0,0};
unsigned long characters[4] = {0x699F99,0x99FF99,0xF6666F,0x666606}; // A, H, I, !
unsigned char messageString[25] = {1,2,3}; // "Hi!"

int messageLength = 3;

void setup() {
 Serial.begin(9600);
 // fillRowStates(0);
 setupLEDs();
 blankLEDs();
}

void loop() {
 for (int messageCharacter=0; messageCharacter < messageLength; messageCharacter++) {
 // load column X for Y letter in message
 for (int characterColumn=4; characterColumn > 0; characterColumn--) {
 shiftDisplayLeft(1,loadCharacterColumn(characterColumn, characters[messageString[messageCharacter]]));
 myDelay(animationWait);
 }
 shiftDisplayLeft(1,0x0);
 myDelay(animationWait);
 shiftDisplayLeft(1,0x0);
 myDelay(animationWait);
 }
 for (int i=0; i<6; i++) {
 shiftDisplayLeft(1,0x0);
 myDelay(animationWait);
 }
}

int loadCharacterColumn(int column, long character) {
 // example character: 0x699F99
 int returnedValue=0;
 int pointer=0;
 Serial.println(character, HEX);
 for (int i=(20+column); i>0; i=i-4) {
 if (bitRead(character,(i-1))) {
 bitSet(returnedValue,pointer);
 } else {
 bitClear(returnedValue,pointer);
 }
 pointer++;
 }
 return returnedValue;
}

void loadCharacter(unsigned long thisCharacter) {
 long newCharacter;
 long shiftValue = 0xF00000;
 // thisCharacter example: 0x699F99
 for(int i=0; i<6; i++) {
 rowStates[(i)] = (shiftValue & thisCharacter) >> (20-(i*4));
 shiftValue = shiftValue >> 4;
 }
}

void shiftDisplayLeft(int steps, int newRows) {
 int newRowMask = 0x20;
 for (int row=5; row > -1; row--) {
 if (newRows & (newRowMask)) {
 rowStates[row] = (rowStates[row] << steps) | (0x000001);
 } else {
 rowStates[row] = (rowStates[row] << steps) & (0xFFFFFE);
 }
 newRowMask = newRowMask >> 1;
 }
}

void fillRowStates(int setToValue) {
 for (int i=0; i < 8; i++) {
 rowStates[i] = setToValue;
 }
}

void lightMatrix() {
 int LEDCount = -1;
 int thisColumnState = 0;

 for (int rowCount = 0; rowCount < numOfRows; rowCount++) {
 lightColumn(rowStates[rowCount]);
 digitalWrite(rowPins[rowCount], HIGH);
 delayMicroseconds(povWait);
 digitalWrite(rowPins[rowCount], LOW);
 }
}

void lightColumn(int columnState) {
 for (int columnCount=0; columnCount < numOfColumns; columnCount++) {
 if (bitRead(columnState,columnCount)==1) {
 digitalWrite(columnPins[columnCount], LOW);
 } else {
 digitalWrite(columnPins[columnCount], HIGH);
 }
 }
}// end of lightColumn

void setupLEDs() {
 // LEDs are forward biased from Row to Column. Rows have the current limiting resistors.
 for (int i=0; i < numOfColumns; i++) {
 pinMode(columnPins[i], OUTPUT);
 digitalWrite(columnPins[i], HIGH); // columns need to stay high, to keep LEDs off even for very brief moments.
 }

 for (int i=0; i < numOfRows; i++) {
 pinMode(rowPins[i], OUTPUT);
 digitalWrite(rowPins[i], LOW); // eliminates the ability for LEDs to turn on
 }
}
void blankLEDs() {
 // the same as the setupLEDs, but this moves a little bit faster!
 for (int i=0; i < numOfColumns; i++) {
 digitalWrite(columnPins[i], HIGH); // columns need to stay high, to keep LEDs off even for very brief moments.
 }

 for (int i=0; i < numOfRows; i++) {
 digitalWrite(rowPins[i], LOW); // eliminates the ability for LEDs to turn on
 }
}

void myDelay(int waitTime) {
 long incomingMills = millis();
 long waitUntilMills = incomingMills + waitTime;

 while(millis() < waitUntilMills) {
 lightMatrix();
 }
}
unsigned long pow2(unsigned long j) {
 unsigned long result=1;
 for(int i=0; i < j; i++) {
 result = result * 2;
 }
 return result;
}

Demonstration

CMiYC Labs

(The old site’s domain name.)

Hello World