Does Zephyr I2C APIs support 16bit register address on ncs v2.4.2?

[snowuyl]

From https://docs.zephyrproject.org/latest/hardware/peripherals/i2c.html link, I didn't find any APIs for 16bit register address. Does Zephyr I2C APIs support 16bit register address on ncs v2.4.2?

[Vidar Berg]

The I2C standard does not support 16-bit device addresses, and the datasheet you referred to shows a 7-bit address (+1 write bit). The second address byte is for the internal register address in the I2C slave and, from the I2C protocol's perspective, it's treated just like any other data byte.

[snowuyl]

Thanks for your reply! I can read/write registers now.

static int _lp5861ReadReg(uint16_t regAddr, uint8_t *regVal) {
    printk("tca6424aReadReg(regAddr=0x%x)\n", regAddr);
    const uint16_t devAddr   = LP5861_CHIP_ADDRESS | _lp5861GetRegAddrHigh(regAddr);
    const uint8_t  startAddr = _lp5861GetRegAddrLow(regAddr);
    printk("devAddr=0x%x, startAddr=0x%x\n", devAddr, startAddr);
    uint8_t rbuf[2];
    const int ret = i2c_burst_read(_gI2cDev, devAddr, startAddr, rbuf, sizeof(rbuf));
    if (ret < 0) {
        printk("i2c_burst_read(0x%x) failed, ret=%d\n", regAddr, ret);
        return ERROR_I2C_READ_FAIL;
    }

    printk("rbuf[0]=0x%x, rbuf[1]=0x%x\n", rbuf[0], rbuf[1]);
    *regVal = rbuf[0];
    return 0;
}

static int _lp5861WriteReg(uint16_t regAddr, uint8_t regVal) {
    printk("tca6424aWriteReg(regAddr=0x%x, regVal0x%x)\n", regAddr, regVal);
    const uint16_t devAddr   = LP5861_CHIP_ADDRESS | _lp5861GetRegAddrHigh(regAddr);
    const uint8_t  startAddr = _lp5861GetRegAddrLow(regAddr);
    printk("_lp5861GetRegAddrHigh(regAddr)=0x%x\n", _lp5861GetRegAddrHigh(regAddr));
    printk("devAddr=0x%x, startAddr=0x%x\n", devAddr, startAddr);
    const uint8_t wbuf[2] = { regVal,  0x00};
    const int ret =  i2c_burst_write(_gI2cDev, devAddr, startAddr, wbuf, sizeof(wbuf));
    if (ret < 0) {
        printk("i2c_burst_write(0x%x) failed, ret=%d\n", regAddr, ret);
        return ERROR_I2C_WRITE_FAIL;
    }

    return 0;
}