Arduino Program to Turn on the First and Tenth LEDs of 8*8 LED Matrix

Previous: Arduino Program to Turn on the First LED

          We have already seen the circuit to connect 8*8 LED matrix to arduino through 8 bit shift register 74595 in previous blog. Next is a simple program to turn on 1^st and 10^th LEDs only and turn off all other LEDs of an 8*8 LED matrix. LED matrix will look like as shown in the following image.

Upload the following program to your arduino board.

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int latchPin = 12;  //Pin connected to ST_CP of 1st 74595
int clockPin = 13;  //Pin connected to SH_CP of 1st 74595
int dataPin = 11;   //Pin connected to DS of 1st 74595

int latchPin2 = 6;  //Pin connected to ST_CP of 2nd 74595
int clockPin2 = 7;  //Pin connected to SH_CP of 2nd 74595
int dataPin2 = 5;   //Pin connected to DS of 2nd 74595

void setup() {
  //set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  
  pinMode(latchPin2, OUTPUT);
  pinMode(clockPin2, OUTPUT);
  pinMode(dataPin2, OUTPUT);
}

void loop() {
  
    /*************************  TURN ON FIRST LED ONLY  ***************************/  
  
    /*** Send HIGH to first Anode pin (16th pin) and LOW to all 
    other anode pins (15, 11, 3, 10, 5, 6, 13) of LED matrix ***/    
  
    // take the latchPin low so the LEDs don't change while you're sending in bits:  
    digitalWrite(latchPin, LOW);
    //Send 0 0 0 0 0 0 0 1 (1) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 1st 74595
    shiftOut(dataPin, clockPin, MSBFIRST, 1);
    // shift out the bits:    
    digitalWrite(latchPin, HIGH);


    /*** Send LOW to the first cathode pin (4th pin) and HIGH to all 
    other cathode pins (7, 2, 8, 12, 1, 14 and 9) of LED matrix ***/    
    
    // take the latchPin low so the LEDs don't change while you're sending in bits:    
    digitalWrite(latchPin2, LOW);
    //Send 1 1 1 1 1 1 1 0 (254) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 2nd 74595
    shiftOut(dataPin2, clockPin2, MSBFIRST, 254);
    // shift out the bits:  
    digitalWrite(latchPin2, HIGH);
    
    
    /**************************  TURN OFF ALL LEDs  ***************************/    
    
    /*** Send LOW to all Anode pins (16, 15, 11, 3, 10, 5, 6, 13) of LED matrix ***/    
  
    // take the latchPin low so the LEDs don't change while you're sending in bits:  
    digitalWrite(latchPin, LOW);
    //Send 0 0 0 0 0 0 0 0 (1) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 1st 74595
    shiftOut(dataPin, clockPin, MSBFIRST, 0);
    // shift out the bits:    
    digitalWrite(latchPin, HIGH);

    /*** Send HIGH to all cathode pins (4, 7, 2, 8, 12, 1, 14 and 9) of LED matrix ***/    
    
    // take the latchPin low so the LEDs don't change while you're sending in bits:    
    digitalWrite(latchPin2, LOW);
    //Send 1 1 1 1 1 1 1 1 (255) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 2nd 74595
    shiftOut(dataPin2, clockPin2, MSBFIRST, 255);
    // shift out the bits:  
    digitalWrite(latchPin2, HIGH);
      
    
    /**************************  TURN ON 10th LED ONLY  ***************************/
   
    /*** Send HIGH to second Anode pin (15th pin) and LOW to all 
    other anode pins (16, 11, 3, 10, 5, 6, 13) of LED matrix ***/    
  
    // take the latchPin low so the LEDs don't change while you're sending in bits:  
    digitalWrite(latchPin, LOW);
    //Send 0 0 0 0 0 0 1 0 (2) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 1st 74595
    shiftOut(dataPin, clockPin, MSBFIRST, 2);
    // shift out the bits:    
    digitalWrite(latchPin, HIGH);

    /*** Send LOW to the first cathode pin (7th pin) and HIGH to all 
    other cathode pins (4, 2, 8, 12, 1, 14 and 9) of LED matrix ***/    
    
    // take the latchPin low so the LEDs don't change while you're sending in bits:    
    digitalWrite(latchPin2, LOW);
    //Send 1 1 1 1 1 1 0 1 (253) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 2nd 74595
    shiftOut(dataPin2, clockPin2, MSBFIRST, 253);
    // shift out the bits:  
    digitalWrite(latchPin2, HIGH);
    
    
    /**************************  TURN OFF ALL LEDs  ***************************/  
    
    /*** Send LOW to all Anode pins (16, 15, 11, 3, 10, 5, 6, 13) of LED matrix ***/    
  
    // take the latchPin low so the LEDs don't change while you're sending in bits:  
    digitalWrite(latchPin, LOW);
    //Send 0 0 0 0 0 0 0 0 (1) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 1st 74595
    shiftOut(dataPin, clockPin, MSBFIRST, 0);
    // shift out the bits:    
    digitalWrite(latchPin, HIGH);

    /*** Send HIGH to all cathode pins (4, 7, 2, 8, 12, 1, 14 and 9) of LED matrix ***/    
    
    // take the latchPin low so the LEDs don't change while you're sending in bits:    
    digitalWrite(latchPin2, LOW);
    //Send 1 1 1 1 1 1 1 1 (255) to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 2nd 74595
    shiftOut(dataPin2, clockPin2, MSBFIRST, 255);
    // shift out the bits:  
    digitalWrite(latchPin2, HIGH);

}

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          If uploading is successfull, 1^st and 10^th LEDs will turn on. All other LEDs will turn off. Here, LED matrix works based on the principle of persistence of vision. Arduino will turn on the 1^st LED. Then turn off all LEDs. After that, arduino will turn on the 10^th LED. Then turn off all LEDs. We all know that an object seen by our eyes will remain in our eyes for next 1/16^th part of a second (persistence of vision). Same principle is used here. Human eye will see the glowing 1^st LED. Within 1/16^th part of a second, eye will see the glowing 10^th LED. Only one LED glows at a time. But the eye will feel that both LEDs are glowing because of persistence of vision. Algorithm to turn on 1^st and 10^th LEDs together is given below.

1. Turn on 1^st LED

          Arduino will shiftout number 1 (0 0 0 0 0 0 0 1) to 1^st 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 0 0 0 0 0 0 0 1. After that, arduino will shiftout number 254 (1 1 1 1 1 1 1 0) to 2^nd 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 1 1 1 1 1 1 1 0. This will turn on 1^st LED.

2. Turn off all LEDs

          Arduino will shiftout number 0 (0 0 0 0 0 0 0 0) to 1^st 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 0 0 0 0 0 0 0 0. After that, arduino will shiftout number 255 (1 1 1 1 1 1 1 1) to 2^nd 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 1 1 1 1 1 1 1 1. This will turn off all LEDs.

3. Turn on 10^th LED

          Arduino will shiftout number 2 (0 0 0 0 0 0 1 0) to 1^st 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 0 0 0 0 0 0 1 0. After that, arduino will shiftout number 253 (1 1 1 1 1 1 0 1) to 2^nd 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 1 1 1 1 1 1 0 1. This will turn on 10^th LED.

4. Turn off all LEDs

          Arduino will shiftout number 0 (0 0 0 0 0 0 0 0) to 1^st 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 0 0 0 0 0 0 0 0. After that, arduino will shiftout number 255 (1 1 1 1 1 1 1 1) to 2^nd 74595. Then Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 will become 1 1 1 1 1 1 1 1. This will turn off all LEDs.

Next: Program to increase the brightness of 1st and 10th LEDs