Two ways to send two or more bytes with nrf_drv_twi_tx

[neosarchizo]

Hi! I use ICM-20602 motion sensor that is similar to MPU6050. Its communication type is also I2C.

I made I2C wrapping module for ICM-20602. In the module, I added i2c_write_byte and i2c_write_bytes functions like following code.

ret_code_t i2c_write_byte(uint8_t dev_addr, uint8_t reg_addr, uint8_t data) 
{
    ret_code_t err_code;
    uint8_t tx_data[2] = { reg_addr, data };

    return nrf_drv_twi_tx(&m_twi_master, dev_addr, tx_data, 2, false);
}

But i2c_write_byte was not like this code. i2c_write_byte was like following code.

ret_code_t i2c_write_byte(uint8_t dev_addr, uint8_t reg_addr, uint8_t data) 
{
    ret_code_t err_code;

    err_code = nrf_drv_twi_tx(&m_twi_master, dev_addr, &reg_addr, 1, true);
    if (err_code != NRF_SUCCESS) return err_code;
    
    err_code = nrf_drv_twi_tx(&m_twi_master, dev_addr, &data, 1, false);
    
    return err_code;
}

But this old i2c_write_byte function did not work well. I think that operations of these i2c_write_byte functions must be an exact match. I read and read again API documents. But results of these i2c_write_byte functions are different. I don't know why. Please explain why results of these i2c_write_byte functions are different.

[RkNg]

Hi, First, i think uint8_t tx_data[2] (1st function) is different from uint8_t data (2nd function), while the nrf_drv_twi_rx require "uint8_t *p_data". It would result in an incompatilble argument error when compiling

And, for I2C, I would suggest that you could use a scope to capture I2C data and see if there is any difference between these 2 functions.

[neosarchizo]

@rknguyen No, no!! I made typos. I modified this post. (data -> &data). I know how to check I2C data as you said. But the reason why I think so is that because nrf_drv_twi_tx function has no_stop parameter. The API docments said like following.

no_stop : If set, the stop condition is not generated on the bus after the transfer has completed successfully (allowing for a repeated start in the next transfer).

So, if I set no_stop to false, and recall nrf_drv_twi_tx function then only one transmission will occur.

I understood like this.

[RkNg]

So,what you got when using these two methods? And what is on your scope ?

[neosarchizo]

@Rknguyen Now, I'm not able to debug two methods. But I will soon update about them! I will not use a scope, I will use a logic analyzer.

[MartinBL]

Can you also show us the code that you use for initializing the TWI driver?