我试图通过 I2C 使用 Raspberry Pi B+ 读取和写入Atmel 24C256 EEPROM，但我无法让它全部正常工作。
这是我到目前为止的代码：
#include <stdio.h>
#include <stdlib.h>
#include <linux/i2c-dev.h>
#include <fcntl.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <linux/i2c.h>
#define DEVICE_PATH "/dev/i2c-1"
#define PAGE_SIZE 64
#define DEVICE_ADDR 0x50 // 0b1010xxxx
int file_desc;
char buffer[PAGE_SIZE + 2]; // 64 bytes + 2 for the address
void teardownI2C()
{
int result = close(file_desc);
}
void setupI2C()
{
file_desc = open(DEVICE_PATH, O_RDWR);
if(file_desc < 0)
{
printf("%s\n", strerror(errno));
exit(1);
}
if(ioctl(file_desc, I2C_SLAVE, DEVICE_ADDR) < 0)
{
printf("%s\n", strerror(errno));
teardownI2C();
exit(1);
}
}
int write_to_device(char addr_hi, char addr_lo, char * buf, int len)
{
struct i2c_rdwr_ioctl_data msg_rdwr;
struct i2c_msg i2cmsg;
char my_buf[PAGE_SIZE + 2];
if(len > PAGE_SIZE + 2)
{
printf("Can't write more than %d bytes at a time.\n", PAGE_SIZE);
return -1;
}
int i;
my_buf[0] = addr_hi;
my_buf[1] = addr_lo;
for(i= 0; i < len; i++)
{
my_buf[2+i] = buf[i];
}
msg_rdwr.msgs = &i2cmsg;
msg_rdwr.nmsgs = 1;
i2cmsg.addr = DEVICE_ADDR;
i2cmsg.flags = 0;
i2cmsg.len = 2+len;
i2cmsg.buf = my_buf;
if(ioctl(file_desc,I2C_RDWR,&msg_rdwr)<0)
{
printf("write_to_device(): %s\n", strerror(errno));
return -1;
}
return 0;
}
int read_from_device(char addr_hi, char addr_lo, char * buf, int len)
{
struct i2c_rdwr_ioctl_data msg_rdwr;
struct i2c_msg i2cmsg;
if(write_to_device(addr_hi, addr_lo ,NULL,0)<0)
{
printf("read_from_device(): address reset did not work\n");
return -1;
}
msg_rdwr.msgs = &i2cmsg;
msg_rdwr.nmsgs = 1;
i2cmsg.addr = DEVICE_ADDR;
i2cmsg.flags = I2C_M_RD;
i2cmsg.len = len;
i2cmsg.buf = buf;
if(ioctl(file_desc,I2C_RDWR,&msg_rdwr)<0)
{
printf("read_from_device(): %s\n", strerror(errno));
return -1;
}
return 0;
}
void fill_buffer(char *buf)
{
int i = 0;
while(i < PAGE_SIZE && *buf)
{
buffer[i+2] = *buf++;
}
while(i++ < PAGE_SIZE-1)
{
buffer[i+2] = '*'; // fill the buffer with something
}
}
int main()
{
setupI2C(); //setup
fill_buffer("Here are some words.");
write_to_device(0x01, 0x00, buffer, PAGE_SIZE);
char newbuf[PAGE_SIZE];
if(read_from_device(0x01, 0x00, newbuf, PAGE_SIZE)>0)
{
printf("%s\n", newbuf);
}
teardownI2C(); //cleanup
return EXIT_SUCCESS;
}
像行中那样写入设备write_to_device(0x01, 0x00, buffer, PAGE_SIZE);不会产生任何错误，但是当我尝试从设备读取数据时，我必须根据规格表写入一个“虚拟”字节，然后尝试从设备读取，但出于某种原因写入虚拟字节会导致错误“输入/输出错误”。我无法弄清楚这是如何工作的。我使用两个资源来指导我，Linux I2C-Dev 文档和来自类似 EEPROM 设备的示例。我有点卡在这里，不知道该尝试什么。非常感谢任何建议或指示！