No related product information!

# Lesson 14 A simple counter

### 1407

Overview

In this lesson, we will program the Arduino MEGA 2560 to make a simple counter.

Requirement

- 1* Arduino MEGA 2560

- 1* USB Cable

- 1* 4-digit 7-segment Display

- 8* 220Ω Resistor

- 2* Button

- Several Jumper Wires

Principle

The 4-digit segment display is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot matrix displays.

4-digit segment displays are widely used in digital clocks, electronic meters, basic calculators, and other electronic devices that display numerical information.

The 4-digit segment display is an 4*8-shaped LED display device composed of 32 LEDs (including four decimal points), these segments respectively named a, b, c, d, e, f, g, h, dig1, dig2, dig3, dig4.

What we used in this experiment is a common cathode 4-digit 7-segment display. Its internal structure is shown below:

The pin number is showing below:

Procedures

1. Build the circuit

2. Program

```/***********************************************************
File name: 14_aSimpleCounter.ino
Description:when you are pressing two buttons, four-digit
segment display values will change.
Author: Tom
Date: 2015/12/27
***********************************************************/
int btn1pin=0;             //Set the digital 0 to button interface
int btn2pin=13;            //Set the digital 13 to button interface
int a = 1;
int b = 2;
int c = 3;
int d = 4;
int e = 5;
int f = 6;
int g = 7;
int p = 8;
int d4 = 9;
int d3 = 10;
int d2 = 11;
int d1 = 12;

long n = 0;
int x = 100;
int del = 55;
int i = 0;
int j = 1;
int k = 2;
int l = 3;
int data;
void setup()
{
pinMode(btn1pin,INPUT_PULLUP); //Set digital 2 port mode, the INPUT for the input
pinMode(btn2pin,INPUT_PULLUP); //Set digital 2 port mode, the INPUT for the input
pinMode(d1, OUTPUT);
pinMode(d2, OUTPUT);
pinMode(d3, OUTPUT);
pinMode(d4, OUTPUT);
pinMode(a, OUTPUT);
pinMode(b, OUTPUT);
pinMode(c, OUTPUT);
pinMode(d, OUTPUT);
pinMode(e, OUTPUT);
pinMode(f, OUTPUT);
pinMode(g, OUTPUT);
pinMode(p, OUTPUT);
}

void loop()
{
int d1,d2,d3,d4;
if(digitalRead(btn1pin)==LOW)          //Detection button interface to low
{
delay(10);                         //Delay 10ms for the elimination of key leading-edge jitter
{
if(data>9999)
{
data=9999;
}else{
data = data + 1;
}
}
}
if(digitalRead(btn2pin)==LOW)          //Detection button interface to low
{
delay(10);                        //Delay 10ms for the elimination of key leading-edge jitter
{
if(data<=0)
{
data=0;
}else{
data = data - 1;
}
}
}
d1 = data/1000%10;    //The one thousand digital data
d2 = data/100%10;     //The one hundred digital data
d3 = data/10%10;      //Ten-digit data
d4 = data%10;         //data of single digit
for(int m=0;m<80;m++){
clearLEDs();           //Turn off all LED lights
pickDigit(1);          //Selection of a digital display
pickNumber(d1);        //Display digital d1
delayMicroseconds(200);

clearLEDs();           //Turn off all LED lights
pickDigit(2);          //Select the first two digital display
pickNumber(d2);        //Display digital d2
delayMicroseconds(200);

clearLEDs();           //Turn off all LED lights
pickDigit(3);          //Select the first three digital display
//dispDec(3);          //Decimal display
pickNumber(d3);        //Display digital d3
delayMicroseconds(200);

clearLEDs();           //Turn off all LED lights
pickDigit(4);          //Select the first four digital display
pickNumber(d4);        //Display digital d4
delayMicroseconds(200);
}
}

void pickDigit(int x)  //Defined pickDigit (x), whose role is to open the port dx
{
digitalWrite(d1, HIGH);
digitalWrite(d2, HIGH);
digitalWrite(d3, HIGH);
digitalWrite(d4, HIGH);
switch(x)
{
case 1:
digitalWrite(d1, LOW);
break;
case 2:
digitalWrite(d2, LOW);
break;
case 3:
digitalWrite(d3, LOW);
break;
default:
digitalWrite(d4, LOW);
break;
}
}

void pickNumber(int x)   //Defined pickNumber (x), whose role is to display digital x
{
switch(x)
{
case 1:
one();
break;
case 2:
two();
break;
case 3:
three();
break;
case 4:
four();
break;
case 5:
five();
break;
case 6:
six();
break;
case 7:
seven();
break;
case 8:
eight();
break;
case 9:
nine();
break;
default:
zero();
break;
}
}

void dispDec(int x)  //Decimal point setting Open
{
digitalWrite(p, HIGH);
}

void clearLEDs()  //Clear screen
{
digitalWrite(a, LOW);
digitalWrite(b, LOW);
digitalWrite(c, LOW);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
digitalWrite(p, LOW);
}

void zero()  //Define those figures 0 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, LOW);
}

void one()  //Define those figures 1 cathode pin switch
{
digitalWrite(a, LOW);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
}

void two()  //Define those figures 2 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, LOW);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, LOW);
digitalWrite(g, HIGH);
}

void three()  //Define those figures 3 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, HIGH);
}

void four()  //Define those figures 4 cathode pin switch
{
digitalWrite(a, LOW);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}

void five()  //Define those figures 5 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, LOW);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}

void six()  //Define those figures 6 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, LOW);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}

void seven()  //Define those figures 7 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
}

void eight()  //Define those figures 8 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}

void nine()  //Define those figures 9 cathode pin switch
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
}```

3. Compile the program and upload to Arduino MEGA 2560 board

Now, when you press one of the two buttons, the value displayed on the 4-digit 7-segment display will be changed.

Summary

By learning this lesson, you'll find that it is so easy to make a simple counter.