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[Reply #15 on:]

I expect it wrap at 256 because you can't fit more than 255 into one byte, so it is wrapping.

Which device do you have? (How many K bits?)

[Reply #16 on:]

If you have the 2 K bit device (that is, 256 bytes) then you won't fit more than 256 bytes into it, so naturally it wraps.

[Reply #17 on:]

Yes Nick, you might be right.

But as I wanted to try to write and read, I have a new issue.

The sketch I'm using :

Code:

#include <Wire.h>     // for I2C
#define i2caddr 0x50    // device address for left-hand chip on our breadboard
byte d=0; // data to store in or read from the EEPROM

void setup()
{
  Serial.begin(9600); // Initialize the serial line
  Wire.begin();         // wake up the I2C
 
  Serial.println("Writing data...");
  for (int i=0; i<255; i++)
  {
    writeData(i,i);
  }
  Serial.println("DONE");
  Serial.println("Reading data...");
  for (int i=0; i<255; i++)
  {
    Serial.print(i);
    Serial.print(" : ");
    d=readData(i);
    Serial.println(d, DEC);
  }
  Serial.println("DONE");

}

// writes a byte of data in memory location addr
void writeData(unsigned int addr, byte data)
{
  Wire.beginTransmission(i2caddr);
  // set the pointer position
  //Wire.write((int)(addr >> 8));
  Wire.write((int)(addr & 0xFF));
  Wire.write(data);
  Wire.endTransmission(1);
  delay(10);
}

// reads a byte of data from memory location addr
byte readData(unsigned int addr)
{
  byte result;
  Wire.beginTransmission(i2caddr);
  // set the pointer position
  //Wire.write((int)(addr >> 8));
  Wire.write((int)(addr & 0xFF));
  Wire.endTransmission(1);
  Wire.requestFrom(i2caddr,1); // get the byte of data
  result = Wire.read();
  return result;
}

void loop()
{
}

The result I got in the Serial monitor that I put in a spread sheet.
You can notice, all the Bytes seems not to be written as they should be.

I modified the 10ms delay in the "writeData" subroutine but nothing change even with 20ms delay instead !

Any Idea ?

[Reply #18 on:]

Code:

#define i2caddr 0x50    // device address for left-hand chip on our breadboard

This comment implies that you also have another eeprom connected as well. You can't have two devices with the same address on the bus.

Pete

[Reply #19 on:]

Hi Pete (El Supremo).

As I said, I'm at the very beginning with I2C EEPROM devices, so I've just copied the code from the web without really understanding what is happening.

You're right about the comment, but I have only 1 EEPROM connected.
So I think it doesn't really matter for my present issue.

[Reply #20 on:]

In the writeData function you must not use Wire.endTransmission(1);
It must be either Wire.endTransmission();  or   Wire.endTransmission(0);

You only use (1) when doing a read - in between writing the address and then issuing the requestFrom.

Pete

[Reply #21 on:]

Hello Pete.

I've changed the (1) with the () ind the write, but it doesn't make any change. Still wrong data in the EEPROM.
The sketch in now as below :

Code:

#include <Wire.h>     // for I2C
#define i2caddr 0x50    // device address
byte d=0; // data to store in or read from the EEPROM

void setup()
{
  Serial.begin(9600); // Initialize the serial line
  Wire.begin();         // wake up the I2C
 
  Serial.println("Writing data...");
  for (int i=0; i<257; i++)
  {
    writeData(i,i);
  }
  Serial.println("DONE");
  Serial.println("Reading data...");
  for (int i=0; i<257; i++)
  {
    Serial.print(i);
    Serial.print(" : ");
    d=readData(i);
    Serial.println(d, DEC);
  }
  Serial.println("DONE");

}

// writes a byte of data in memory location addr
void writeData(unsigned int addr, byte data)
{
  Wire.beginTransmission(i2caddr);
  // set the pointer position
  //Wire.write((int)(addr >> 8));
  Wire.write((int)(addr & 0xFF));
  Wire.write(data);
  Wire.endTransmission();
  delay(10);
}

// reads a byte of data from memory location addr
byte readData(unsigned int addr)
{
  byte result;
  Wire.beginTransmission(i2caddr);
  // set the pointer position
  //Wire.write((int)(addr >> 8));
  Wire.write((int)(addr & 0xFF));
  Wire.endTransmission(1);
  Wire.requestFrom(i2caddr,1); // get the byte of data
  result = Wire.read();
  return result;
}

void loop()
{
}

By the way. I'm having so hard time with this I2C EEPROM, would you have any good link with some sketches very well explained. I haven't been able to find something that could help me properly yet !

At the end, my project is to reprogram a Laser printer chip.
So, read an EEPROM (brand new and already programmed), then, write the data to the old one, so I've got a spare one.

I'll need some advice to do this. I've already read the data of the new 24C04.
I'll now need to inject these data in the old one.

[Reply #22 on:]

At the end of writeData you have a delay. Try replacing it with this code:

Code:

    while(1) {
      Wire.beginTransmission(i2caddr);
      if(Wire.endTransmission() == 0)break;
    }

This code waits until the device has finished writing (it won't respond until it is done). But your delay of 20ms should be plenty of time to finish a write. It's worth a try.

I'm using larger EEPROMs (e.g. 24LC1026) but other than that your code is the same as mine.

Pete

[Reply #23 on:]

Here's my attempt to read/write to a 24LC256 EEPROM using I2C:

http://www.gammon.com.au/forum/?id=10896&reply=2#reply2

[Reply #24 on:]

Hi.

Sorry for the late response but I was on something else these time.

To make it working, I needed to power up the Arduino  through an external 12VDC power supply instead of the USB cable from the computer or even a 5vDC supply through Vin of the ARDUINO.

I also replace the delay by El Supremo's piece of code witch I thing is much more clever than wasting time with Delay and being not sure that the job is done !

But the problem was raelly the power supply of the ARDUINO. At least it now works fine.

Now I'm sure the writing and reading is ok, how can I write the proper number in each piece of memory ?

See, I've read the Eeprom I want to copy so I stored all the data in an open office format as .ods (OoCalc)or .odt (OoWriter) format)
1/   Read the data
2/   Copy from the SerialMonitor
3/   Paste in a calc or writer page to save the data in a safe place.

But I don't know how to program the new Eeprom with these data.
I'm not going to write each data at a time in the serial monitor. here must be a better way for sure.

Any advice.

How I can put these data in ?

[Reply #25 on:]

I recently intefaced with a similar EEPROM, 24LC01. I used the EEPROM24 library, which is really simple. Strongly reccomended, and support all kinds if 24xCxx EEPROMS