Read and Write TWI Sensor Registers

[CMan1]

Hi there,

I'm developing with the nRF52840 right now.

I'm trying to read some sensordata with TWI. The sensors are BMM150, BMI270 and BMP388.

Unfortunately, I already have problems with the my first sensor (BMM150), reading the Chip ID.

To read it, I have to set the Power Control Bit of the sensor. That seems to be working.

But when I want to read registers again, I only get zeros. Even for reading the Power Control Bit.


This is the function to write Registers:

bool writeRegister(uint8_t regNumber, uint8_t value){
  ret_code_t err_code;

  uint8_t valueBuffer[2];
  valueBuffer[0] = regNumber;
  valueBuffer[1] = value;
  err_code = nrf_drv_twi_tx(&m_twi, 0x10, valueBuffer, sizeof(valueBuffer), false);
  APP_ERROR_CHECK(err_code);
  return 1;
}

Read Registers:

uint8_t readRegister(uint8_t regNumber){
  ret_code_t err_code;

  uint8_t resultsWhoAmI;
  uint8_t whoAmIPointer = regNumber;
  err_code = nrf_drv_twi_tx(&m_twi, 0x10, &whoAmIPointer, 1, true);
  err_code = nrf_drv_twi_rx(&m_twi, 0x10, &resultsWhoAmI, 1);
  APP_ERROR_CHECK(err_code);

  return resultsWhoAmI;
}



Main to test reading the Chip ID. Later on I want to use the Bosch Sensortec API. But first I want this one to work:
int main(void)
{
    ret_code_t err_code;
    uint8_t address = 0x10;
    uint8_t read_data;
    uint8_t write_data;

 
    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_LOG_INFO("Read Chip ID started");

    NRF_LOG_FLUSH();
    twi_init();

    // Read Power Control Bit
    read_data = readRegister(0x4B);
    uint8_t pwr_bit = read_data & 0b1;
    NRF_LOG_INFO("Read Power Control = %x", pwr_bit);
    NRF_LOG_FLUSH();

    write_data = read_data | 1;
    writeRegister(0x4B, write_data);
    NRF_LOG_INFO("Set Power Control Register to %x", write_data & 0b1);
    NRF_LOG_FLUSH();

    read_data = readRegister(0x4B);
    pwr_bit = read_data & 0b1;
    NRF_LOG_INFO("Read Power Control = %x", pwr_bit);
    NRF_LOG_FLUSH();


    read_data = readRegister(0x4C);
    uint8_t opMode = (read_data | 0b110) >> 1;
    NRF_LOG_INFO("Read MODE = %x", opMode);
    NRF_LOG_FLUSH();

    write_data = read_data | 0b00000110;
    writeRegister(0x4b, write_data);
    NRF_LOG_INFO("Set Mode Register to: %x", (write_data & 0b110)>>1);
    NRF_LOG_FLUSH();

    read_data = readRegister(0x4C);
    opMode = (read_data | 0b110) >> 1;
    NRF_LOG_INFO("Read MODE = %x", opMode);
    NRF_LOG_FLUSH();

    nrf_delay_ms(5000);

    read_data = readRegister(0x4B);
    pwr_bit = read_data & 0b1;
    NRF_LOG_INFO("Read Power Control = %x", pwr_bit);
    NRF_LOG_FLUSH();

    read_data = readRegister(0x40);
    NRF_LOG_INFO("Chip ID = %x", read_data);
    NRF_LOG_FLUSH();

}



This is the Output: 

I've already read a couple of posts where others also had trouble reading on the bus after something was written. However, I couldn't find a solution.

Maybe somethings wrong with my code. I hope you could help me.


Thank you.

[CMan1]

I just created a minimal example to reproduce the issue.

I used the bmm150.

In the first write operation I set the power control bit to 1 (has to be done to read the chip id). 

When I just do this WRITE Operation the reading of the chip ID works fine.

But if I write the mode register beforehand (without changing anything), the reading of the Chip ID doesn't work anymore.

I hope this helps to reproduce the issue

#include <stdio.h>
#include "boards.h"
#include "app_util_platform.h"
#include "app_error.h"
#include "nrf_delay.h"

// include I2C Lib
#include "nrf_drv_twi.h"

// include LOG Libs
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"


/* TWI instance ID. */
#define TWI_INSTANCE_ID     0

/* TWI instance. */
static const nrf_drv_twi_t m_twi = NRF_DRV_TWI_INSTANCE(TWI_INSTANCE_ID);


/**
 * @brief TWI initialization.
 */
void twi_init (void)
{
    ret_code_t err_code;

    const nrf_drv_twi_config_t twi_config = {
       .scl                = SCL0_PIN,
       .sda                = SDA0_PIN,
       .frequency          = NRF_DRV_TWI_FREQ_100K,
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = true
    };

    err_code = nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
    APP_ERROR_CHECK(err_code);

    nrf_drv_twi_enable(&m_twi);
}

bool writeRegister(uint8_t regNumber, uint8_t value){
  ret_code_t err_code;

  uint8_t valueBuffer[2];
  valueBuffer[0] = regNumber;
  valueBuffer[1] = value;
  err_code = nrf_drv_twi_tx(&m_twi, 0x10, valueBuffer, sizeof(valueBuffer), false);
  APP_ERROR_CHECK(err_code);
  return 1;
}

uint8_t readRegister(uint8_t regNumber){
  ret_code_t err_code;

  uint8_t resultsWhoAmI;
  uint8_t whoAmIPointer = regNumber;
  err_code = nrf_drv_twi_tx(&m_twi, 0x10, &whoAmIPointer, 1, false);
  err_code = nrf_drv_twi_rx(&m_twi, 0x10, &resultsWhoAmI, 1);
  APP_ERROR_CHECK(err_code);

  return resultsWhoAmI;
}


/**
 * @brief Function for main application entry.
 */
int main(void)
{
    ret_code_t err_code;
    uint8_t address = 0x10;
    uint8_t read_data;
    uint8_t write_data;
    
    nrf_delay_ms(00);
 
    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_LOG_INFO("Read Chip ID started");

    NRF_LOG_FLUSH();
    twi_init();

    nrf_delay_ms(500);

    // Read Power Control Bit
    read_data = readRegister(0x4B);
    uint8_t pwr_bit = read_data & 0b1;
    NRF_LOG_INFO("Read Power Control = %x", read_data);
    NRF_LOG_FLUSH();

    write_data = read_data | 1;
    writeRegister(0x4B, write_data);
    NRF_LOG_INFO("Set Power Control Register to %x", write_data & 0b1);
    NRF_LOG_FLUSH();

    read_data = readRegister(0x4B);
    pwr_bit = read_data & 0b1;
    NRF_LOG_INFO("Read Power Control = %x", pwr_bit);
    NRF_LOG_FLUSH();


    read_data = readRegister(0x4C);
    uint8_t opMode = (read_data | 0b110) >> 1;
    NRF_LOG_INFO("Read MODE = %x", opMode);
    NRF_LOG_FLUSH();

    write_data = read_data | 0b00000110;
    writeRegister(0x4b, write_data);
    NRF_LOG_INFO("Set Mode Register to: %x", (write_data & 0b110)>>1);
    NRF_LOG_FLUSH();


    while(1){
      nrf_delay_ms(500);
      read_data = readRegister(0x4B);
      pwr_bit = read_data & 0b1;
      NRF_LOG_INFO("Read Power Control = %x", pwr_bit);
      NRF_LOG_FLUSH();

      read_data = readRegister(0x40);
      NRF_LOG_INFO("Chip ID = %x", read_data);
      NRF_LOG_FLUSH();
   }
}