eeprom!

[gordon111]

I have been trying to program 'n EEPROM ( 24LC128 ) for the whole week, but i am not succeeding.

my code follows:

include <16F883.h>
//#fuses HS, NOWDT, PROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#use i2c(MASTER, sda=PIN_C3, scl=PIN_C4)
#case
unsigned int8 address;
unsigned char data;
unsigned char value;

// Writes to the slave board from the master.
void write_ext_eeprom(unsigned int8 address, unsigned char data)
{

i2c_start();
i2c_write(0xa0);
i2c_write(address>>8);
i2c_write(address);
i2c_write(data);
i2c_stop();

}

// Read from the slave board and display the data.
unsigned int16 read_ext_eeprom(unsigned int8 address )
{

i2c_start();
i2c_write(0xA0);
i2c_write(address>>8);
i2c_write(address);
i2c_start();
i2c_write(0xA1);
data = i2c_read(0);
i2c_stop();

return data;

}



//====================================
void main()
{

TRISA = 0x0A; // Port A Direction
// RA0 : Sensor Input (0)
// RA1 : Sensitivity Input (1)

// RA2 : Not used (0)
// RA3 : Not used (1)
// RA4 : Not used (0)
// RA5 : Not used (0)

TRISB = 0x00; // Port B Direction
// RB0 : Not used (0)
// RB1 : RS-485 Direction Output (0)
// RB2 : LED1 Output (0)
// RB3 : LED2 Output (0)
// RB4 : LED3 Output (0)
// RB5 : RUN LED Output (0)
// RB6 : Not used (0)
// RB7 : Not used (0)

TRISC = 0x80; // Port C Direction
// RC0 : Not used (0)
// RC1 : Not used (0)
// RC2 : Relay Output (0)
// RC3 : SCLK (0)
// RC4 : SDAT (0)
// RC5 : Not used (0)
// RC6 : Serial Transmit (0)
// RC7: Serial Recieve {1)

while(1)

{

write_ext_eeprom(1,100);
read_ext_eeprom(1);
value = data;
printf("\r\n\-----> Tempratuur_waarde = 0x%D", value );


}

}


my result is, 255 or 0xff.

please help!

[PCM programmer]

Your driver routines are not correct. The 24LC128 uses two bytes
for the address. Your functions only accept one byte (int8) as the
address.

Also, it takes time to complete the write operation. At then end of
the write routine, you need to either put in a fixed delay time of at
least 5 ms (this is in the data sheet) or do "ack polling" (this is also
in the data sheet).

Also, in your read routine, you don't declare the 'data' variable
as a local variable. You need to do that. Don't use a global.

Look at other CCS eeprom drivers for examples.

[gordon111]

thanx alot for the help,

must i state somewhere that i am using a 24LC128 in my code?Or is this not necessary?

[gordon111]

Hey,

I have made all the changes you said, and it still doesn't return the correct values. Please help!

[ckielstra]

[vanSittert]

After making all the changes you suggested, the only value that is returned is 0xFF!

i do not know, what i am doing wrong at all!

[Ttelmah]

Obvious comment, but I have not seen it made so far in the thread. You have got the pull up resistors on the SCL/SDA lines?...

Best Wishes

[gordon111]

Hey,

Obvious and well noted comment, thanx, but i checked i have 2k7 pull up to Vcc on both!

[ckielstra]

I don't know the difference, but have you checked the 24C128 driver in the CCS program directory?

One important difference is that in your code you have a 5ms delay in the write routine but at the wrong place, just before the i2c_stop while it should be after the i2c_stop instruction:

[gordon111]

Thank you again for the advice, this was an obvious error, unfortuanetly this didn't fixs the problem!

[Ttelmah]

Other obvious comment, how have you got the address lines wired?. Address A0, requires all the lines to be held low.

Best Wishes

[rnielsen]

For now, try placing actual values for the address into your functions, instead of trying to pass the address value. This might help to confirm if the communication is working between the master and the eeprom. Also, try to place an if() in there to see if the eeprom is talking properly. Something like:

[gordon111]

Hey,

Thanks for all the help, it finally work.I wrote the wrong control byte,
A2 = 0, A1 = 0 and A0= 0 was accually all pulled up high to VCC

Thanks again for all the help.

Gordon