how to specifically initialize the I2C pin on NRF52832?

[vishal]

when trying to initialize the nrf52...little bit confused how to specifically address a pin for i2c....can anyone help me with a piece of code. Thank you in advance.

[Jørgen Holmefjord]

TWI sensor example should work fine, but you need to modify it to read and write the correct registers.

[asmita_patil]

yes..m just trying to read revision id register (0x81)...it is supposed to return 21..i am new to twi

Fullscreen vcnl4020_main.c Download

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/** @file
 * @defgroup tw_sensor_example main.c
 * @{
 * @ingroup nrf_twi_example
 * @brief TWI Sensor Example main file.
 *
 * This file contains the source code for a sample application using TWI.
 *
 */

#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. */
#define vcnl4020_ADDR          (0x13U>>1) 

#define vcnl4020_REG_command                           0x80U
#define vcnl4020_REG_PRODUCT_ID_REVISION_REGISTER      0x81U
#define LM75B_REG_THYST     0x02U
#define LM75B_REG_TOS       0x03U

/* 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;

    

/**
 * @brief Function for setting active mode on MMA7660 accelerometer.
 */
ret_code_t vcnl4020_set_mode()
{
    ret_code_t err_code;

    /* Writing to LM75B_REG_CONF "0" set temperature sensor in NORMAL mode. */
    uint8_t reg[1] = {0x80};                                  
    err_code = nrf_drv_twi_tx(&m_twi, vcnl4020_ADDR, reg, sizeof(reg), false);
    APP_ERROR_CHECK(err_code);
    while (NRF_DRV_TWI_EVT_DONE == false);
     return (err_code);

    /* Writing to pointer byte. */
   reg[0] = vcnl4020_REG_PRODUCT_ID_REVISION_REGISTER;
    m_xfer_done = false;
    err_code = nrf_drv_twi_tx(&m_twi, vcnl4020_ADDR, reg, 1, false);
    APP_ERROR_CHECK(err_code);
    while (m_xfer_done == false);
}

/**
 * @brief Function for handling data from temperature sensor.
 *
 * @param[in] temp          Temperature in Celsius degrees read from sensor.
 */
__STATIC_INLINE void data_handler(uint8_t temp)
{
    NRF_LOG_INFO("Temperature: %d Celsius degrees.", temp);
}

/**
 * @brief TWI events handler.
 */
void twi_handler(nrf_drv_twi_evt_t const * p_event, void * p_context)
{
    switch (p_event->type)
    {
        case NRF_DRV_TWI_EVT_DONE:
            if (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_RX)
            {
                data_handler(m_sample);
            }
            m_xfer_done = true;
            break;
        default:
            break;
    }
}

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

    const nrf_drv_twi_config_t twi_lm75b_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_lm75b_config, twi_handler, NULL);              //non-blocking mode...in blocking mode no twi_handler in provided and doen not uses interrupt
    APP_ERROR_CHECK(err_code);

    nrf_drv_twi_enable(&m_twi);
}

/**
 * @brief Function for reading data from temperature sensor.
 */
static int read_sensor_data()
{
    m_xfer_done = false;
    bool t;
    uint32_t event;
    ret_code_t err_code,err;
    uint8_t reg[1] = {0x81U};
  err_code = nrf_drv_twi_tx(&m_twi, vcnl4020_ADDR, &reg[0], 1, false);
  APP_ERROR_CHECK(err_code);


//  if(err_code != NRF_SUCCESS) {
//    return err_code;
//  }

    /* Read 1 byte from the specified address - skip 3 bits dedicated for fractional part of temperature. */
//   err_code=(0x13U>>1);

   err = nrf_drv_twi_rx(&m_twi, vcnl4020_ADDR, &m_sample, sizeof(m_sample));
   event = nrf_drv_twi_stopped_event_get(&m_twi);
   t = nrf_drv_twi_is_busy(&m_twi);            // true  If the TWI driver is currently busy performing a transfer
    while(m_xfer_done==false);
    APP_ERROR_CHECK(err);
    return (err_code);
    return (m_sample);
}

/**
 * @brief Function for main application entry.
 */
int main(void)
{
    ret_code_t rslt;
   uint8_t out_t;
    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();
//  vcnl4020_set_mode();

    while (true)
    {
//        nrf_delay_ms(500);
//
//        do
//        {
//            __WFE();
//        }while (m_xfer_done == false);
//
    rslt =  read_sensor_data();
        NRF_LOG_FLUSH();
    }

}
/** @} */

this is what i am doing...the code is getting stuch at " while(m_xfer_done==false);"

t = nrf_drv_twi_is_busy(&m_twi);   function returns true indicating that it is busy..why is nrf52832 is busy reading register... i am not understanding...will you help..

thank you for your reply