作为第一步(在读取和写入之前),您必须确保您的 SPI 接口(硬件和软件)配置正确。要检查此步骤,您可以从 25LC1024 中读取“状态寄存器”。查看“RDSR”的数据表,发送到 eeprom 的指令应该是 0b00000101 所以(int)5。
这里有一些 18F* + 25LC* 的代码,写在一个非常古老的项目的 sdcc 中。该代码非常基本,没有使用外部库,您只需为您的图片替换寄存器变量名和初始化配置。
一些代码来自这里,感谢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
注意:由于 25LC1024 的地址是 3x8 位,请确保您的编译器“长”类型至少有 24 位
#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
主程序
根据数据表设置您的初始化
#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);
}
如果您想读/写缓冲区,请注意分页。例如这里:
// 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