how i can write long num in eeprom and read

Projects Programming
1

Where I got the highest value is 256

Thanks for your help

#include <EEPROM.h>

void setup ()
{
Serial.begin(9600);
}

void loop ()
{
EEPROM.write( 0,EEPROM.read(0)+1);
Serial.println( EEPROM.read(0));
delay(100);
}

2

That's because a EEPROM memory location is just 8-bit. I think you try to store an int? An int is 16-bit on an Arduino. So you need 2 EEPROM memory locations. Something like:

void writeEepromInt(int value, int location){
  EEPROM.write(location, value);
  EEPROM.write(location + 1, value >> 8);
}

int readEepromInt(int location){
  int val;

  val = (EEPROM.read(location + 1) << 8);
  val |= EEPROM.read(location);

  return val;
}

Keep in mind that if you store an int at address 0 with this function it's actually stored at address 0 and 0! So don't try to store something at 2 as well, use 2 for the next.

3

It appears from your title that you want to store a long data type, not an int. Is that correct?

4

If you are trying to write a long, this might help you see how to do it:

#include <EEPROM.h>

union {
  byte array[sizeof(long)];   // Change if for an int
  long bigNum;
} myUnion;

void setup() {
  // put your setup code here, to run once:
  int i;
  Serial.begin(115200);
  
  long val = 123456;
  long back;
  
  myUnion.bigNum = val;
  Serial.println(myUnion.bigNum);
  for (i - 0; i < sizeof(long); i++) {
    EEPROM.write(myUnion.array[i], i);
  }
  Serial.println("Read back from EEPROM:");
  for (i - 0; i < sizeof(long); i++) {              // Change both for loops for an int
    myUnion.array[i] = EEPROM.read(i);
  }
  back = myUnion.bigNum;
  Serial.println(back);   
}

void loop() {
  // put your main code here, to run repeatedly:

}

You can easily adapt the code for an int if that's what you need.

5

Thanks for your help my friends

Forgive me, but give me an example of that possible if i want to add No. 123456 in eeprom

And how to read and write

6

Man, we did! Looking at the code it should not be that hard. If it is, look harder and learn :slight_smile:

7

Forgive me, but give me an example of that possible if i want to add No. 123456 in eeprom

log2123456 = 16.913, so you're going to need at least 17 bits to represent it, so at least three bytes of EEPROM.

8

septillion:
That's because a EEPROM memory location is just 8-bit. I think you try to store an int? An int is 16-bit on an Arduino. So you need 2 EEPROM memory locations. Something like:

void writeEepromInt(int value, int location){

EEPROM.write(location, value);
  EEPROM.write(location + 1, value >> 8);
}

int readEepromInt(int location){
  int val;

val = (EEPROM.read(location + 1) << 8);
  val |= EEPROM.read(location);

return val;
}




Keep in mind that if you store an int at address 0 with this function it's actually stored at address 0 and 0! So don't try to store something at 2 as well, use 2 for the next.

Newbie alert!

The shift (thingy?) << 8, that code writes the the first 8 bits of the Int, then shifts it to the last 8?

If we have the value of 12,568 (b11000100011000) that will write 00011000 to location, and 110001 (assuming 2 leading zeros, maybe leading 10 for positive? not sure how the sign is stored in an int) to location +1?

Any good resources/tutorials on this topic?

EDIT: Bah! On page two! http://forum.arduino.cc/index.php?topic=303786.0