reading external sensor using i2c

[ps_anu]

hi...

i want to read the  external accelerometer sensor using i2c in nRF52832 ..how to do ?

[Amanda Hsieh]

Hi, 

You could start from the TWI Sensor Example which use the I2C interface by communicating with the thermometer (LM75).

-Amanda H. 

[ps_anu]

i have connected externally  the accelerometer sensor in scl and sda pin of nrf52832 . but i am not getting any data 

[Amanda Hsieh]

What is the accelerometer sensor, based example project and SDK you are using?

What did you modify the project?

Have you tried debugging your application? Could you provide the debug log?

-Amanda H. 

[ps_anu]

i didn't modify anything . i am using MMA7760 accelerometer sensor ,15.2 v

[Amanda Hsieh]

Hi, 

If you google MMA7760, the first result points to the datasheet: https://www.nxp.com/docs/en/data-sheet/MMA7660FC.pdf

In the MODES OF OPERATION section in that datasheet the interfaces are described (I2C).

If you download the SDK we have the TWI Sensor Example to show how to use TWI. However, it does not suit for MMA7760. 

And the TWI driver is documented here: TWI 

You could modify the TWI_SENSOR example to configure the twi driver correctly to match the sensor and transmitting the correct commands. I would say that it does not matter what example you use as the template as long as the configuration for twi drvier does suit the sensor. And unfortunately, we do not have any example for that accelerometer. 

-Amanda H.

[ps_anu]

Hi... Amanda

i tried .. but i am getting constantly 0 as a value . see the code 

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


#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

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

/* Common addresses definition for temperature sensor. */


/* Mode for LM75B. */
#define NORMAL_MODE 0U

/* Indicates if operation on TWI has ended. */
static volatile bool m_xfer_done = false;

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

/* Buffer for samples read from temperature sensor. */
static uint8_t m_sample;








uint32_t device_addr    =0x4C ;

 uint32_t register_addr= 0x00;

 uint8_t *p_data;


void twi_init (void)
{
    ret_code_t err_code;

    const nrf_drv_twi_config_t twi_config  = {
       .scl                = ARDUINO_SCL_PIN,
       .sda                = ARDUINO_SDA_PIN,
      .frequency          = NRF_DRV_TWI_FREQ_100K,
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = false
    };

     err_code = nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
   
    APP_ERROR_CHECK(err_code);
    if (NRF_SUCCESS == err_code)
	{
		nrf_drv_twi_enable(&m_twi);
		NRF_LOG_INFO("TWI init success...");	
}
}


static void read_register()
{
  ret_code_t err_code;
  nrf_drv_twi_t twi_instance;
  uint32_t device_addr    =0x4C ;


 uint32_t register_addr=   0x00;
  uint8_t *p_data; uint8_t bytes;
  bool no_stop;

 err_code = nrf_drv_twi_tx(&twi_instance, device_addr, &register_addr, 1, no_stop);
  APP_ERROR_CHECK(err_code);

  if(err_code != NRF_SUCCESS) {
    return err_code;
  }
  err_code = nrf_drv_twi_rx(&twi_instance, device_addr, p_data, bytes);
return err_code;
}




int main(void)
{
    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_LOG_INFO("\r\nTWI sensor example started.");
    NRF_LOG_FLUSH();
    twi_init();
   read_register();

   
    while (1)
    {
        nrf_delay_ms(500);
           NRF_LOG_INFO("\r\nTWI .");
printf("p_data:%d",p_data);
NRF_LOG_INFO("P_data:%d",p_data);
NRF_LOG_FLUSH();
    
}
}