I2C EEPROM : 可写但只读 0xFF

Question

我目前正在研究 i.MX6（Android BSP）和 24C08WP EEPROM 之间的 I2C 通信。

我运行在 i.MX6 上是一个二进制文件，之前是在 Linux 下的 NDK 下编译的。

借助 i2cdetect 工具，我检测到连接到 i.MX6 的 I2C 总线（地址 0x50）的 NTAG 5 组件。

使用以下代码，我可以执行写入操作，我可以使用 Arduino 板和 I2C 读取操作进行检查。

但是，当我在i.MX6下对用户space执行读取操作时，我只得到0xFF值。

这是我的代码：

#include <stdio.h>
#include <stdlib.h>

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include <linux/i2c-dev.h>

#include "board.h"
#include "debug_tools.h"
#include "boardselection.h"

int main(void) {
    int file;
    int adapter_nr = 1; /* probably dynamically determined */
    char filename[20];

    snprintf(filename, 19, "/dev/i2c-%d", adapter_nr);
    file = open(filename, O_RDWR);
    if (file < 0) {
        /* ERROR HANDLING; you can check errno to see what went wrong */
        exit(1);
    }

    int addr = 0x50; /* The I2C address */

    if (ioctl(file, I2C_SLAVE, addr) < 0) {
        /* ERROR HANDLING; you can check errno to see what went wrong */
        exit(1);
    }

    uint8_t reg = 0x00;

    uint8_t data_w[4] = {0x00, 0x00, 0x00, 0x00};

    data_w[0] = reg;
    data_w[1] = 0x01;
    data_w[2] = 0x02;
    data_w[3] = 0x03;
    
    /* Write the register */
    if (write(file, data_w, 4) != 4)
    {
        perror("Failed to write to the i2c bus");
        exit(1);
    }

    usleep(2000000);

    uint8_t data_r[4] = {0x00, 0x00, 0x00, 0x00};

    if (read(file, data_r, 3) != 3) {
        /* ERROR HANDLING: i2c transaction failed */
        perror("Failed to read register value");
        exit(1);
    }

    /* data_r[0] contains the read byte */
    printf("%X %X %X\n", data_r[0], data_r[1], data_r[2]);

    return 0;
}

你能帮帮我吗？

描述了关于接收 0xFF 值的几乎相同的问题。

Answer 1

正如@Andrew Cottrell 在中所说：“要从您的 I2C 设备读取，假设它使用一个字节的寄存器，写入一个字节的缓冲区（寄存器地址）然后读取一个或多个字节的缓冲区（该寄存器和后续寄存器中的值）。

所以正确的代码如下：

#include <stdio.h>
#include <stdlib.h>

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include <linux/i2c-dev.h>

#include "board.h"
#include "debug_tools.h"
#include "boardselection.h"

int main(void) {
    int file;
    int adapter_nr = 1; /* probably dynamically determined */
    char filename[20];

    snprintf(filename, 19, "/dev/i2c-%d", adapter_nr);
    file = open(filename, O_RDWR);
    if (file < 0) {
        /* ERROR HANDLING; you can check errno to see what went wrong */
        exit(1);
    }

    int addr = 0x50; /* The I2C address */

    if (ioctl(file, I2C_SLAVE, addr) < 0) {
        /* ERROR HANDLING; you can check errno to see what went wrong */
        exit(1);
    }

    uint8_t reg = 0x00;

    uint8_t data_w[4] = {0x00, 0x00, 0x00, 0x00};

    data_w[0] = reg;
    data_w[1] = 0x44;

    /* Write the register */
    if (write(file, data_w, 2) != 2)
    {
        perror("Failed to write to the i2c bus");
        exit(1);
    }

    usleep(1000000);

    uint8_t data_r[4] = {0x00, 0x00, 0x00, 0x00};

    if (write(file, &reg, 1) != 1)
    {
        perror("Failed to write to the i2c bus");
        exit(1);
    }

    if (read(file, data_r, 1) != 1) {
        /* ERROR HANDLING: i2c transaction failed */
        perror("Failed to read register value");
        exit(1);
    }

    /* data_r[0] contains the read byte: 0x44 */
    printf("%02X\n", data_r[0]);

    return 0;
}

N.B.: 如果在两次写操作之间不使用usleep()等待，第二次写操作可能会失败。

I2C EEPROM : 可写但只读 0xFF

I2C EEPROM : can write but read only 0xFF

linux

i2c

eeprom