How To Save A Text In The EEPROM Of The Arduino- (Part 21/49)

The size of the EEPROM memory available in the Arduino board varies from one kind of board to another. The arduino board is built around an AVR microcontroller burned with arduino boot-loader providing all the necessary circuitry for the microcontroller to operate. The arduino board used in this project is the arduino pro-mini board which has an ATMEGA328 microcontroller having an internal EEPROM of size 1Kb. The pro-mini board also one set of Tx and Rx pins which can be used to connect the board with serial communication lines. In this project the pro-mini board is programmed using the Arduino IDE version 1.0.3 downloaded for windows.

The image of the Arduino pro-mini board and the Arduino IDE is shown in the following;

Fig. 1: Typical Arduino Pro-Mini Board

Fig. 2: Arduino IDE Software Window

Since the arduino pro-mini board has no circuitary for interfacing it with the serial port or the USB port of the PC, an external USB to TTL converter board is required to connect it with the PC. This hardware helps in programming the arduino board and also helps in the serial communication with the PC through the USB port of the PC.

Fig. 3: External USB to TTL converter board for programming Arduino and serial communication

It is assumed that the reader has gone through the project how to get started with the arduino and done all the things discussed in it. The Arduno IDE is very easy to start with and has lot of built in libraries and function for every simple and complex tasks. The Arduino IDE also has a library called <EEPROM.h> which provides functions to access the built-in EEPROM of the Arduino board’s microcontroller. The code written for this project also makes use of few functions from the <EEPROM.h> to read and write the built-in EEPROM. The functions are namely EEPROM.write() and EEPROM.read() and the details of those functions are already discussed in previous projects on how to read and write the EEPROM of the Arduino, how to test the EEPROM of the Arduino and how to save a sensor value in the EEPROM of the Arduino.

The Arduino IDE also provide some built-in functions which helps in the serial communication process. There is a function which helps to initialize the serial communication port with a particular baud rate and there are functions to send data to the serial port and read data from the serial port. The functions used in this projects are namely Serial.begin(), Serial.print(),Serial.println(), Serial.available(),Serial.read() and Serial.write(). The details of these functions and similar functions for the serial communication are already discussed in previous projects on how to do serial communication with the Arduino, how to send and receive serial data using arduino, how to do serial debugging with the Arduino.

The project also displays some text on the LCD with the help of the functions from the library <LiquidCrystal.h>. The important functions provided by the library <LiquidCrystal.h> are already used and explained in previous projects on how to interface an LCD, how to display sensor value on LCD, how to connect the LCD with the PC and how to make an LCD scrolling display.

In this project an LED is connected to the pin number 6 of the Arduino board which serves the purpose of indicating each data byte written by blinking once and also blinking continuously after the EEPROM runs out of memory. The LED is controlled by using the built-in functions of the Arduino IDE namely pinMode(),digitalWrite() and delay() which are discussed in the previous projects on how to get started with the Arduino, how to use digital input and output of the Arduino.

THE CODE

The code written for this project configures the pin number 6 as output pin where an LED indicator is connected using the function pinMode(). The LCD is the initialized using the function lcd.begin() and generates an initial display in the 16*2 LCD screen. The function Serial.begin() is then used to initialize the serial port with a baud rate of 9600. The code then reads the entire EEPROM memory using the function EEPROM.read() and send the data as previously saved text to the serial port using the function Serial.write(). The entire EEPROM memory is then cleared by writing it with white spaces using the function EEPROM.write() before the new text is read into. The code then waits till the user input text data bytes using the function Serial.available(). As the serial data is available it is written to the successive memory locations using the function EEPROM.write() along with blinking an LED connected to the pin number 6 for each data byte written using the function digitalWrite(). Once the EEPROM of the Arduino runs out of memory the LED is blinked continuously using the functions digitalWrite() and delay().

When the coding is finished one can verify and upload the code to the Arduino board as explained in the project how to get started with the Arduino. The Arduino board can then be connected to the PC using USB to TTL converter board and the previous text can be viewed or new text can be typed into using any serial monitoring software or using the Arduino IDE’s serial monitoring software itself as explained in the project how to do serial debugging with the Arduino.

Fig. 4: Arduino EEPROM Read Write Circuit Setup On Breadboard

Project Source Code

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/*================================= EG LABS =======================================

The code for saving a text in the EEPROM and read it back when powered up

 

 The circuit:

 * LED attached from pin 6 to ground through a 1K resistor

 

 LCD:

 * LCD RS pin to digital pin 12

 * LCD Enable pin to digital pin 11

 * LCD D4 pin to digital pin 5

 * LCD D5 pin to digital pin 4

 * LCD D6 pin to digital pin 3

 * LCD D7 pin to digital pin 2

 * LCD R/W pin to ground

 * 10K resistor:

 * ends to +5V and ground

 * wiper to LCD pin 3

 * LED anode attached to digital output 6

 * LED cathode attached to ground through a 1K resistor

//================================= EG LABS =======================================*/



#include <EEPROM.h>

#include <LiquidCrystal.h>


LiquidCrystal lcd(12, 11, 5, 4, 3, 2);               // initialize the LCD library with the numbers of the interface pins

int address = 0;                                     // the variable which holds the address in the eeprom

int read_value = 0;                                  // the variable which holds the data which is read from the eeprom

char serial_in_data;                                 // the variable which holds serial input data

int led = 6;                                         // variable which holds the pin number at which the LED is connected

int i;

void setup()

{

  pinMode(led, OUTPUT);                               // initialize the led pin as an output.

  lcd.begin(16, 2);                                   // set up the LCD's number of columns and rows: 

  lcd.print("ENGINEERS GARAGE");                      

  lcd.setCursor(0, 1);   

  lcd.print(" SERIAL  EEPROM ");

  Serial.begin(9600);                                 // initialize the serial port with baud rate 9600

  Serial.println();

  Serial.println("PREVIOUS TEXT IN EEPROM :-");

  for(address = 0; address < 1024; address ++)        // read the entire EEPROM memory

  {  

    read_value = EEPROM.read(address);

    Serial.write(read_value);

  }

  Serial.println();

  Serial.println("WRITE THE NEW TEXT : ");

  

  for(address = 0; address < 1024; address ++)        // fill the entire eeprom memory with white spaces

    EEPROM.write(address, ' ');                 

  

  for(address = 0; address < 1024; )                  // write the incoming serial data to the EEPROM

  {

    if(Serial.available())

    {

      serial_in_data = Serial.read();  

      Serial.write(serial_in_data); 

      EEPROM.write(address, serial_in_data); 

      address ++;

      digitalWrite(led, HIGH);       

      delay(100);

      digitalWrite(led, LOW);

    }

  }

}


void loop()

{

  //---- blink LED -----//

  digitalWrite(led, HIGH);       

  delay(1000);

  digitalWrite(led, LOW);

  delay(1000);

  //---- blink LED -----//

}

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Circuit Diagrams

Circuit-Diagram-Saving-Text-EEPROM-Arduino

Project Components

Project Video