ISL1208时钟芯片 Linux下 i2c 读写示例。

#include 
#include 
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#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#define DEVICE_NAME "/dev/i2c-1"
#define I2C_ADDR 0x6f // i2c设备地址

static int i2c_write_bytes(int fd, uint8_t slave_addr, uint8_t reg_addr, uint8_t *values, uint8_t len)
{
    uint8_t *outbuf = NULL;
    struct i2c_rdwr_ioctl_data packets;
    struct i2c_msg messages[1];
    outbuf = (uint8_t *)malloc(len + 1);
    if (!outbuf)
    {
        printf("Error: No memory for buffer\n");
        return -1;
    }

    outbuf[0] = reg_addr; // i2c设备要操作的reg地址
    memcpy(outbuf + 1, values, len);

    messages[0].addr = slave_addr; // i2c设备地址
    messages[0].flags = 0;         // write flag
    messages[0].len = len + 1;
    messages[0].buf = outbuf; // 向reg写入的值

    /* Transfer the i2c packets to the kernel and verify it worked */
    packets.msgs = messages;
    packets.nmsgs = 1;
    if (ioctl(fd, I2C_RDWR, &packets) < 0)
    {
        printf("Error: Unable to send data");
        free(outbuf);
        return -1;
    }

    free(outbuf);

    return 0;
}

static int i2c_read_bytes(int fd, uint8_t slave_addr, uint8_t reg_addr, uint8_t *values, uint8_t len)
{
    uint8_t outbuf[1];
    struct i2c_rdwr_ioctl_data packets;
    struct i2c_msg messages[2];

    outbuf[0] = reg_addr;          // i2c设备要操作的reg地址
    messages[0].addr = slave_addr; // i2c设备地址
    messages[0].flags = 0;         // write flag
    messages[0].len = sizeof(outbuf);
    messages[0].buf = outbuf;

    /* The data will get returned in this structure */
    messages[1].addr = slave_addr;                     // i2c设备地址
    messages[1].flags = I2C_M_RD /* | I2C_M_NOSTART*/; // write flag
    messages[1].len = len;
    messages[1].buf = values;

    /* Send the request to the kernel and get the result back */
    packets.msgs = messages;
    packets.nmsgs = 2;
    if (ioctl(fd, I2C_RDWR, &packets) < 0)
    {
        printf("Error: Unable to send data");
        return -1;
    }

    return 0;
}

int main()
{
    int fd;
    bool cmdIsRd = false;
    char *arg_ptr = NULL;
    unsigned long len;
    unsigned int slave_addr, reg_addr;
    uint8_t buffer[1024];

    /* 2.打开I2C总线 */
    fd = open(DEVICE_NAME, O_RDWR);
    if (fd < 0)
    {
        printf("can not open file %s\n", DEVICE_NAME);
        return -1;
    }
    len = 2;
    buffer[0] = 0x11;
    buffer[1] = 0x12;
    // Alarm
    i2c_write_bytes(fd, I2C_ADDR, 0x0c, buffer, len);
    // RTC
    len = 12;
    i2c_read_bytes(fd, I2C_ADDR, 0x00, buffer, len);

    printf("read data =");
    for (int i = 0; i < len; i++)
    {
        printf("0x%02X ", buffer[i]);
    }
    printf("\n");

    return 0;
}

一、设备地址是8bit
1、i2cdetect检测有几组i2c总线

               i2cdetect -l

2、i2cdetect检测挂载在i2c总线上器件

               i2cdetect-r -y 1（检测i2c-1上的挂载情况）

3、i2cdump查看器件所有寄存器的值

             i2cdump -f -y 1 0x50 （查看i2c-1总线上0x50设备的所有寄存器值）

4、i2cset设置单个寄存器值

              i2cset -f -y 1 0x50 0x01 0xaa （往i2c-1总线上0x50设备0x01寄存器写0xaa）

5、i2cget读取单个寄存器值

               i2cget -f -y 1 0x50 0x01     （读取i2c-1总线上0x50设备0x01寄存器的值）

二、设备地址是16bit
例子：i2c总线1上挂设备，设备地址是 0x3020 ，要读取16个字节
              i2ctransfer -y -f 1 w2@0x10 0x30 0x20 r16
#w是写，2是写入2个字节，@0x10是寄存器地址，030 0x20是寄存器要设置的地址的高低位，r是读取，16 是读取16个字节

例子：i2c总线1上挂设备，设备地址是 0x3020 ，要写16个字节数据，数据是0x55 0xaa
                i2ctransfer -y -f 1 w4@0x10 0x30 0x20 0x55 0xaa
#w是写，4是写入4个字节，@0x10是寄存器地址，0x30 0x20是寄存器要设置的地址的高低位，0x55 0xaa是要写入的值