Saving data to External EEPROM with PIC18 - c

Question

I have PIC18F87J11 with 25LC1024 external EEPROM, and I would like to store some data on it and be able to read it later on. I have done some research, but unfortunately I could not find a tutorial that uses similar board as mine. I am using MPLAB IDE with C18 compiler.
PIC18F87J11
Note: two more links are written as comment below.
This is where my problem is ...
In order to write to the 25LC1024 external EEPROM I followed the tutorial from microchip. The first problem is that this tut is written for PIC18F1220 and I'm using PIC18F87J11. So upon opening the project I get two files not found error, but I simply ignored them.
PICTURE
I copied the file AN1018.h and AN1018_SPI.c to the project I am working on, and I copied some piece of code from AN1018.c file.
Code from AN1018.c file
void main(void)
{
#define PAGESIZE 16
static unsigned char data[PAGESIZE]; // One-page data array
static unsigned char i;
init(); // Initialize PIC
data[0] = 0xCC; // Initialize first data byte
/* Low-density byte function calls */
LowDensByteWrite(data[0], 0x133); // Write 1 byte of data at 0x133
data[0] = 0xFF;
LowDensByteRead(data, 0x133);
printf("%x",data);
while(1){};
}
void init(void)
{
ADCON1 = 0x7F; // Configure digital I/O
PORTA = 0x08; // Set CS high (inactive)
TRISA = 0b11110111; // Configure PORTA I/O
PORTB = 0; // Clear all PORTB pins
TRISB = 0b11111100; // Configure PORTB I/O
}
My second problem is that the output message is always 1e0. In other words, I do not know if the write was successfully made or not. Also I am not sure about what I might be missing.
If I can receive some kind of help, I would appreciate it. To sum up everything, I want to store data to my external EEPROM and retain it when needed. Please know I am a beginner with Microcontroller programming.

Answer 1

As a first step (before reading & writing) you have to be sure that your SPI interface (hardware and software) is correctly configured. To check this step you can read the "Status Register" from the 25LC1024. Look the datasheet for "RDSR", the instruction to send to the eeprom should be 0b00000101 so (int)5.
Here some code for 18F* + 25LC* wirtten in sdcc of a really old project. The code is very basic, no external library used, you just have to replace register variable names and init config for your pic.
Some code comes from here, thanks to bitberzerkir!
spi.c
#ifndef SPI_HH
#define SPI_HH
#define SpiWrite(x) spiRW(x)
#define SpiRead() spiRW(0)
unsigned char spiRW(unsigned char data_){
SSPBUF = data_;
while(!PIR1bits.SSPIF);
PIR1bits.SSPIF = 0;
return SSPBUF;
}
void SpiInit() {
SSPSTAT = 0x40; // 01000000
SSPCON1 = 0x20; // 00100000
PIR1bits.SSPIF = 0;
}
#endif
eeprom.c
Note: Since the addr of 25LC1024 are 3x8bits make sure your compiler 'long' type has at least 24bit
#ifndef EEPROM_HH
#define EEPROM_HH
#include "spi.c"
#define CS PORTCbits.RC2
void EepromInit() {
SpiInit();
CS = 1;
}
unsigned char EReadStatus () {
unsigned char c;
CS = 0;
SpiWrite(0x05);
c = SpiRead();
CS = 1;
return c;
}
unsigned char EWriting() {
unsigned char c;
CS = 0;
SpiWrite(0x05);
c = SpiRead();
CS = 1;
return c & 1;
}
unsigned char EReadCh (unsigned long addr) {
unsigned char c;
// Send READ command and addr, then read data
CS = 0;
SpiWrite(0x03);
// Address in 3x8 bit mode for 25lc1024
SpiWrite(addr>>16);
SpiWrite(addr>>8);
SpiWrite((unsigned char) addr);
c = SpiRead();
CS = 1;
return c;
}
void EWriteCh (unsigned char c, unsigned long addr) {
// Enable Write Latch
CS = 0;
SpiWrite(0x06);
CS = 1;
// Send WRITE command, addr and data
CS = 0;
SpiWrite(0x02);
SpiWrite(addr>>16);
SpiWrite(addr>>8);
SpiWrite((unsigned char) addr);
SpiWrite(c);
CS = 1;
}
#endif
main.c
Set your init according to the datasheet
#include <pic18fregs.h>
#include "eeprom.c"
void main(void) {
char out;
TRISB = 0x01;
TRISC = 0x00;
PORTB = 0x00;
PORTC = 0x00;
EepromInit();
EWriteCh('a', 0x00);
out = EReadCh(0x00);
while(1);
}
If you want to read/write a buffer take care of pagination. Eg here:
// Page byte size, 64 for 25lc256 and 256 for 25lc1024
#define PSIZE 256
// Addr mem limit 7FFF for 25lc256, 1FFFF for 25lc1024
#define MLIMIT 0x1FFFF
void EReadBuff (unsigned char c[], unsigned long dim, unsigned long addr) {
unsigned int i;
// Send READ command and addr, then read data
CS = 0;
SpiWrite(0x03);
SpiWrite(addr>>16);
SpiWrite(addr>>8);
SpiWrite((unsigned char) addr);
for(i = 0; i < dim; ++i)
c[i] = SpiRead();
CS = 1;
}
void EWriteBuff (unsigned char c[], unsigned long dim, unsigned long addr) {
unsigned char i;
unsigned int begin = 0;
unsigned int end = dim > PSIZE ? PSIZE : dim;
while (end > begin && addr + end <= MLIMIT) { // check if addr is a siutable address [0, MLIMIT]
// Enable Write Latch
CS = 0;
SpiWrite(0x06);
CS = 1;
// Send WRITE command, addr and data
CS = 0;
SpiWrite(0x02);
SpiWrite(addr>>8);
SpiWrite((unsigned char) addr);
for(i = begin; i < end; ++i)
SpiWrite(c[i]);
CS = 1;
while(EWriting());
dim -= PSIZE;
begin += PSIZE;
addr += PSIZE;
end = begin + (dim > PSIZE ? PSIZE : dim);
}
}
#endif

Answer 2

I think before directly using the AN1018.h/AN1018_spi.c you will need to verify that it is compatible with your micro-controller. I recommend to check the datasheet of both micro-controllers and see the difference specifically for SPI module as the external EEPROM which you are using will be connected to SPI bus. If these two micro-controller has same register configuration/module for SPI then you can use it else you will have to write the driver on your own. You can use AN1018_spi.c for reference I guess you will just need to change some registers if required.
Then in you init function, you are not initializing SPI module, you will need to specify correct SPI clock, SPI mode based on your external device. Once you have properly initialize SPI module. You will need to write EEPROM_Read/EEPROM_Write function. In which you will have to following protocol given in datasheet of your external device for sending/receiving data from device using.

Answer 3

hi i googled and get a very good website Where i found post on Interfacing external EEPROM with PIC Microcontroller via i2c protocol with FM24C64 and the code which they given in post which i tested and working fine. i give that link may it help you. http://www.nbcafe.in/interfacing-external-eeprom-with-pic-microcontroller/