Read data from 16bit register TWI on NRF52833.

Question

Hi All, 
 I am trying to communicate with IC MAX17201 using I2C interface. I am able to detect the IC and communicate with it. 
 When I read 8bit registers from the IC I don't have any issue. But when I am trying to read 16bit register from the IC, I am getting errors.The existing code from NRF SDK includes data to read and write 8 bit registers. 
 I have modified the code a bit in order to read 2bytes from register. I am not able to read 16bit registers. I tried to read NPACKCFG_REG but not able to read it properly. As well as while compiling I am getting warnings like this:-unsigned conversion from 'int' to 'uint8_t' {aka 'unsigned char'} changes value from '437' to '181' [- 
 #define NPACKCFG_REG 0x1B5

#define MAX17201_ADDRESS_LEN 1 
#define MAX17201_ADDR (0xD8>>1) 
#define MAX17201_WHO_AM_I 0x6BU 

bool i2c_register_write_max17211(uint16_t register_address, uint16_t value)
{

 ret_code_t err_code;
 uint8_t tx_data[4];

 tx_data[0] = ( (register_address >> 8)& 0xFF );
 tx_data[1] = register_address & 0xFF;
 tx_data[2] = ((value>>8)& 0xff);
 tx_data[3] = value & 0xFF;

 m_xfer_done = false;
 
 err_code = nrf_drv_twi_tx(&m_twi, MAX17201_WHO_AM_I, tx_data, sizeof(tx_data), false);
 //Wait until the transmission of the data is finished
 while (m_xfer_done == false)
 {
 }

 // if there is no error then return true else return false
 if (NRF_SUCCESS != err_code)
 {
 NRF_LOG_INFO("FAILED");
 return false;
 }

 NRF_LOG_INFO("SUCCESS");

 return true;	

}

bool i2c_register_read_max17211(uint8_t register_address, uint8_t destination[2], uint8_t number_of_bytes)
{
 ret_code_t err_code;
 //uint8_t rx_buffer[2];

 //Set the flag to false to show the receiving is not yet completed
 m_xfer_done = false;
 
 // Send the Register address where we want to write the data
 err_code = nrf_drv_twi_tx(&m_twi, MAX17201_WHO_AM_I, &register_address, 1, true);
 
 //Wait for the transmission to get completed
 while (m_xfer_done == false){}
 //vTaskDelay(1000);

 // If transmission was not successful, exit the function with false as return value
 if (NRF_SUCCESS != err_code)
 {
 return false;
 }

 //set the flag again so that we can read data from the MPU6050's internal register
 m_xfer_done = false;
 
 // Receive the data from the MPU6050
 //err_code = nrf_drv_twi_rx(&m_twi, MAX17201_WHO_AM_I, destination, number_of_bytes);
 err_code = nrf_drv_twi_rx(&m_twi, MAX17201_WHO_AM_I, &destination[0], sizeof(destination));
 
 //wait until the transmission is completed
 while (m_xfer_done == false){}
 //vTaskDelay(1000);


 // if data was successfully read, return true else return false
 if (NRF_SUCCESS != err_code)
 {
 return false;
 }
 
 //NRF_LOG_INFO("DATA IS %x",destination);
 return true;

} 
 
 Please help me on how to read multiple bytes from 16bit registers and how to write data into 16 bit registers.

Jørgen Holmefjord · Accepted Answer

It should be very similar to your write function. Something like this will probably work (not tested):

bool i2c_register_read_max17211(uint16_t register_address, uint16_t *value)
{
    ret_code_t err_code;
    uint8_t tx_buffer[2];
	uint8_t rx_buffer[2];
	
	tx_buffer[0] = ( (register_address >> 8) & 0xFF);
    tx_buffer[1] = register_address & 0xFF;

    //Set the flag to false to show the receiving is not yet completed
    m_xfer_done = false;
    
    // Send the Register address where we want to write the data
    err_code = nrf_drv_twi_tx(&m_twi, MAX17201_WHO_AM_I, tx_buffer, sizeof(tx_buffer), true);
	  
    //Wait for the transmission to get completed
    while (m_xfer_done == false){}
    //vTaskDelay(1000);

    // If transmission was not successful, exit the function with false as return value
    if (NRF_SUCCESS != err_code)
    {
        return false;
    }

    //set the flag again so that we can read data from the MPU6050's internal register
    m_xfer_done = false;
	  
    // Receive the data from the MPU6050
    //err_code = nrf_drv_twi_rx(&m_twi, MAX17201_WHO_AM_I, destination, number_of_bytes);
    err_code = nrf_drv_twi_rx(&m_twi, MAX17201_WHO_AM_I, rx_buffer, sizeof(rx_buffer));
		
    //wait until the transmission is completed
    while (m_xfer_done == false){}
    //vTaskDelay(1000);


    // if data was successfully read, return true else return false
    if (NRF_SUCCESS != err_code)
    {
        return false;
    }
	*value = (rx_buffer[0] << 8);
    *value |= rx_buffer[1];
    
    //NRF_LOG_INFO("DATA IS %x",destination);
    return true;

}

Read data from 16bit register TWI on NRF52833.

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