External EEPROM write and read

[Guest]

Hi

I´m trying to write and read an external EEPROM (24LC256), I´m entering information using a serial port, this information is added to a buffer variable until a press "Enter", Once I press enter the information is written in the external EEPROM Memory, When I read the memory addresses written I just see 0xFF, Here It´s the program:

#include <16f877.h> // PIC Selection
#fuses HS,NOWDT,NOPROTECT,NOLVP,PUT,BROWNOUT
#use delay(clock=20000000)
#use rs232(baud=1200,parity=N,xmit=PIN_B1,rcv=PIN_B0,bits=8,stream=PC)
#use rs232(baud=1200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,stream=PBX)
#define EEPROM_SDA PIN_A1
#define EEPROM_SCL PIN_A0 //pines for the EEPROM
#include <24256.c> //librery eeprom 24LC256

////////////////////////////////////////////////////////////////////////////////

// Constants
int const MAXLENBUFF=68;
int commandx=0;

// Globals Variables ///////////////////////////////////////////

char buffrec[MAXLENBUFF]; // Reception Buffer
int xbuffrec=0x00; // Buffer index
int xbuffrecw=0x00;

int1 new_command=0; // Flag for writting EEPROM

void Add_buffrec(char c); // add a character to reception buffer
void write_EEPROM(void); // sub for EEPROM writing


// INTERRUPTIONS ////////////////////////////////////////////////////////////////


/******************************************************************************/
/* varibles for handlign read and write

int row=0;
int pagact=0;
int t=0;
int conta=0;

/// Funtion Declaration/////////////////////////////////////////////////

void Ini_buffrec(void); // Reception buffer
void Add_buffrec(char c); // Add a character to buffer
void read_buffrec(char s); // read EEPROM
/************************************************************
/// Interruption from PBX serial port

#int_rda
rda_isr() {
char vari;
vari=fgetc(PBX); // save character coming from PBX in vari
Add_buffrec(vari); //call sub for add to buffer variable

}
/********* Interruption from serial port (RB0)************/

#int_EXT // RB0 Interruption
ext_isr() {
char varif;
varif=fgetc(PC);
read_buffrec(varif); //call read EEPROM sub-rutine
}

//****************Add character to buufer variable

void Add_buffrec(char c){

switch(c){
case 0x0D: // Check if enter was hit
buffrec[xbuffrec++]=c; //include "enter" in buffer variable
new_command=1; // Flag to indicate end of receive
conta=conta+1; //Counter for bytes receive
break;
default:
buffrec[xbuffrec++]=c; // add character Buffer variable

conta=conta+1; //Counter for bytes receive
}
}

//****************************************************************************************

///write information in EEPROM*********************

void Escribir_EEPROM(void){
int i;
if (row>=186){ //Check if EEPROM is full
fila=0;
t=0;
pagact=0;
fprintf(PC,"row=0\n\r");
}
for(i=0;i<conta;i++){ // write information receive in EEPROM
write_ext_eeprom(row,buffrec);
row=row+1;
}
conta=0;
}

//********************************************
//Read information from the EEPROM and send it to PC serial port
void Leer_buffrec(char s){
if(s=='I'){ //Wait for "I" Characrter
for(t=pagact; t<row; t++){
fputc(read_ext_eeprom(t),PC); // read EEPROM/
}
pagact=t; //Save last EEPROM adress read and write
}
}

// Buffer Variable clear ---------------------------------------

void Ini_buff_rec(void){

int i;
for(i=0;i<MAXLENBUFF;i++){ //
buffrec=0x00; // All buffer variable to 0
}
xbuffrec=0x00; //
conta=0x00; // counter to 0
}

/*************** Main Routing************************/

void main() {

ext_int_edge(H_TO_L); // Enable interruption H_to_L Pin RB0
enable_interrupts(INT_EXT); // Enable external interruption RB0
enable_interrupts(int_rda); // Enable RDA(received Data Available)
enable_interrupts(GLOBAL); // Enable global interruption

init_ext_eeprom();
Ini_buff_rec();

fprintf(PBX,"Trying PBX\n\r");
fprintf(PC,"Trying PC\n\r");



do {

if(new_command==1){
new_command=0; // Clear variable
Escribir_EEPROM(); // Call Write EEPROM
Ini_buff_rec(); // call clear buffer
}

} while(TRUE);// LOOP

I try this program for the internal EEPROM of the 16F877 and It works (Using write_eeprom and read_eeprom functions), I`m using 3.236 PCWH compiler. Appreciate any help

[PCM programmer]

Do you have pull-up resistors on the SDA and SCL lines ?
You need them.

Do you have address pins A0, A1, and A2 on the eeprom
connected to ground ? They should be.

The WP pin should be left unconnected. It has an internal pull-down
resistor.

[lexer]

Thanks PCM programmer, (I forgot to login when I started the post). Yes I have the SDA and the SCL lines resistors, But I dont have A0, A1 and A2 to ground let me try?

[PCM programmer]

Actually, if it's a Microchip 24LC256, the data sheet says those pins
also have internal pull-down resistors.

What brand of eeprom do you have ? Is it Microchip ?

[lexer]

Yes I`m using a Microchip memory, I was thinking If the format of the variable for addessing the the memory could be the problem, The manual tells that It has to be a 16 bit address. The data to write has to be a char o could any type?[/i]

[PCM programmer]

First you could do a simple test to see if the hardware is working.
See the test program that I've posted near the start of this thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=23824
It just writes 0x55 and 0xAA to the eeprom. Then it reads it back
and displays it on a terminal window. See if that program works.

Remember to change the #define statements for the pins,
near the top of the program, to the pins that you are using (A0 and A1).

[lexer]

Thanks, I simulate your program with Proteus, I display the read addresses (0 and 1) in VTERM, I dont see the values 0x55 and 0xAA in the VTERM but If I check the EEPROM debug I see that addresses 0 and 1 have 0x55 and 0xAA, The values in VTERM arent HEX neither decimal, Any Idea?