# Lesson 21: Using Seven Segment Display | Arduino Step by Step Course

### Part 2: LCD, LED and OLED Screens

In this lecture we learn how to use seven segment display direclty with Arduino.

``````
/*
*  Robojax Arduino Step By Step Course
* Lesson 21  Seven Segment Display
* Display number on seven segment display with Arduino

Please watch video instruction here https://youtu.be/pxUjEsJQW2M
This code is available at http://robojax.com/course1/?vid=lecture11

with over 100 lectures Free On  YouTube Watch it here http://robojax.com/L/?id=338
Get the code for the course: http://robojax.com/L/?id=339
* Written by Ahmad Shamshiri for Robojax Robojax.com
* on December 07, 2018 at 22:34 in Ajax, Ontario, Canada

*
* This code is "AS IS" without warranty or liability. Free to be used as long as you keep this note intact.*
* This code has been download from Robojax.com
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

#define type 1 // 0 for common cathode and 1 for common acode

const int displayPins[7] = {2,3,4,5,6,7,8}; // define pins
const int dicimalPoint = 9;// decimal point

// array for seven segment LED values. Do not change.
//This is used for both common anode and common cathode
byte displayLEDs[10][7] = {
{ 0,0,0,0,0,0,1 },  // = 0
{ 1,0,0,1,1,1,1 },  // = 1
{ 0,0,1,0,0,1,0 },  // = 2
{ 0,0,0,0,1,1,0 },  // = 3
{ 1,0,0,1,1,0,0 },  // = 4
{ 0,1,0,0,1,0,0 },  // = 5
{ 0,1,0,0,0,0,0 },  // = 6
{ 0,0,0,1,1,1,1 },  // = 7
{ 0,0,0,0,0,0,0 },  // = 8
{ 0,0,0,0,1,0,0 }   // = 9
};
/*
*
* @brief wites digit to display
* @param digit (integer)
* @return no return value
* Written by Ahmad Shamshiri on Friday Dec 07, 2018 for Robojax.com
*/
void writeDigit(int digit) {
// Robojax Seven Segment Display for Arduino
Serial.print(digit);
Serial.print(" ");

int digitValue;
for (int i=0; i < 7; i++)
{

digitalWrite(displayPins[i], convertHighLow(displayLEDs[digit][i]));// write the HGIH or LOW (depending on the type) to output pin
Serial.print(convertHighLow(displayLEDs[digit][i]));// print the result to the Serial monitor

}// for i
}//writeDigit ends here

/*
*
* @brief converts HIGH and LOW based on the "type" variable value
* if type is 1, converts the "V" to LOW, or returns it as it is if type if 0 (zero)
* @param v (integer)
* @return the convertedValue
* Written by Ahmad Shamshiri (Robojax.com) on Friday Dec 08, 2018 for Robojax.com
*/
int convertHighLow(int v)
{
int convertedValue;
if(type ==0)
{
convertedValue = 1 - v;// if common anode, change the HIGH to LOW and LOW to HIGH
}else{
convertedValue = v;// if common cathode, keep it the same
}

return convertedValue;
}

void setup() {
// Robojax Seven Segment Display for Arduino
//Robojax Arduino Step By Step Course http://robojax.com/L/?id=338
for(int d=0; d<8; d++)
{
pinMode(displayPins[d], OUTPUT);// set pin as output

}
pinMode(dicimalPoint,OUTPUT);// define a pin for decimal pint
digitalWrite(dicimalPoint,HIGH);// turn decimal point OFF. Set to LOW if common Anode and HIGH for common cathode

Serial.begin(9600);// initialize serial monitor with 9600 baud
}// setup ends here

void loop() {
// Robojax Seven Segment Display for Arduino
//Robojax Arduino Step By Step Course http://robojax.com/L/?id=338
for (int i=0; i<=9 ; i++) {
writeDigit(i);
Serial.println("=====");
delay(1000);
}
digitalWrite(dicimalPoint,LOW);// turn decimal point ON
delay(3000);
// writeDigit(4);
// delay(3000);

}// loop ends here

```  ```

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