can not get data from i2c_read()

[Van]

Hi,

After I wrote to EEPROM, I would like to read it back, but I can not. What I got back is just 0xFF, here is the code:

void init_ext_eeprom()
{
output_float(EEPROM_SCL);
output_float(EEPROM_SDA);

}
BOOLEAN ext_eeprom_ready()
{
int ack;
i2c_start(); //if the write command is acknowledged
ack = i2c_write(0xa0); //then the device is ready
i2c_stop();
return !ack;

}
void write_ext_eeprom(long int address, BYTE data)
{
while(! ext_eeprom_ready() );

i2c_start();
i2c_write(0xa0);
i2c_write(address);
i2c_write(data);
i2c_stop();
delay_ms(10);

}
int read_ext_eeprom(long int address)
{
int data, data1;
i2c_start();
i2c_write(0xa0);
i2c_write(hi(address) );
i2c_write(address);

i2c_start();
i2c_write(0xa1);
data = i2c_read(0);
data1 = i2c_read();
i2c_stop();
return data;

}

void main()
{
int i, j;
init_ext_eeprom();
for(i = 0; i < 3; i++)
{
write_ext_eeprom(i, 10+i);

}
for(i = 0; i < 3; i++)
{
j = ext_read_eeprom(i); // I can not get back the data at address 0

}

}

After I wrote from address 0 to address 3, then I would like to read it back from address 0 to address 3. But I could not, Could you please help me to solve this?

Thank you for your time and your help
Van

[PCM programmer]

int read_ext_eeprom(long int address)
{
int data, data1;
i2c_start();
i2c_write(0xa0);
i2c_write(hi(address) );
i2c_write(address);

i2c_start();
i2c_write(0xa1);
data = i2c_read(0);
data1 = i2c_read();
i2c_stop();
return data;

}
------------------------------------------------------------------


Your code above is incorrect. You should only use the "0" parameter
with i2c_read() only on the last read. It should be like this:

data = i2c_read();
data1 = i2c_read(0);

Also, are you aware that you're only returning the first byte
of the two that you're reading ?

[Van]

int read_ext_eeprom(long int address)
{
int data, data1;
i2c_start();
i2c_write(0xa0);
i2c_write(hi(address) );
i2c_write(address);

i2c_start();
i2c_write(0xa1);
data = i2c_read();

i2c_stop();
return data;

}
------------------------------------------------------------------
PCM programmer!

I still could not get back to data from the EEPROM? As I am debugging those, the line
data = i2c_read()
return the value 0xFF
Could you please tell me why I can not read back a value that I wrote to?
Thank for your help
Van

[PCM programmer]

For the last i2c read, you must use a "0" parameter. Example:

data = i2c_read(0);

[Van]

That is it, the problem has sovled

Thank you, PCM programmmer, for your time and knowledge

Van

[Chill]

Hi all,

I have the I2C issue something like the above post.

The PIC18f65j10 works as a master to read the eeprom data back,
The code as below,

[PCM programmer]

It's not a fix, it's part of the i2c specification. Look on page 10, at
the last paragraph on the right side of the page. It says this:

[Chill]

Got it. Thanks, PCM programmer.