linux 读写i2c设备,使用Linux通过I2C读写EEPROM

乐正雕漆

911人浏览 · 2021-05-06 16:21:12

乐正雕漆 · 2021-05-06 16:21:12 发布

我尝试通过I2C读取和写入带有Raspberry Pi B的Atmel 24C256 EEPROM,但是我无法正常工作.

这是我到目前为止的代码：

#include

#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;

}

写入设备,如行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时,我必须根据规格表写一个“虚拟”字节,然后尝试从设备读取但由于某种原因写入虚拟字节会导致错误“输入/输出错误”.我无法弄清楚它是如何工作的.我正在使用两个资源来指导我,Linux I2C-Dev documentation和similar EEPROM device.的一个例子我有点卡在这里,不知道该尝试什么.任何建议或指针都非常感谢！

解决方法:

或者,如果您能够为Raspberry Pi编译和安装不同的内核设备树,则可以通过内核at24.c驱动程序访问它.

内核设备树需要指定EEPROM的类型和地址,以及它连接的I²C总线.我不确定Raspberry Pi,但对于BeagleBone Black EEPROM,它是这样的：

&i2c0 {

eeprom: eeprom@50 {

compatible = "at,24c32";

reg = <0x50>;

};

对于您的设备,您需要指定compatible =“at,24c256”;

确保内核配置指定CONFIG_EEPROM_AT24 = y(或= m).

然后,您应该能够从/ sys / bus / i2c / devices / 0-0050 / eeprom或/ sys / bus / i2c / drivers / at24 / 0-0050 / eeprom等用户空间访问EEPROM存储器.

标签：c-3,linux,raspberry-pi,i2c,eeprom