twi, mpu650 + hmc5883l

[omar]

HI, i m beginner in TWI with nrf52832. i want to write a bit in a registre of hmc5883l but i didnt succeed. what i want to do is :

writeByte(devAddr, regAddr, b) ==> ( 0x1E,0x37,1)

tgis my own code that i tried but i didn't understand why is not working! help if u can

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

#define NRF_LOG_MODULE_NAME "APP"

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

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

 /* Number of possible TWI addresses. */
 #define TWI_ADDRESSES      127

/* 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                = ARDUINO_SCL_PIN,
       .sda                = ARDUINO_SDA_PIN,
       .frequency          = NRF_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);

    nrf_drv_twi_enable(&m_twi);
}


/**
 * @brief Function for main application entry.
 */
bool writeBit()
{
		
		uint8_t packet[1] = {0x37};
		ret_code_t err_code;
		err_code = nrf_drv_twi_tx(&m_twi,(0x1E),packet,sizeof(packet),false);
		APP_ERROR_CHECK(err_code);


   return err_code;
}

int main(void)
{
    ret_code_t err_code;
    uint8_t address;
    uint8_t sample_data;
		uint8_t data;
    bool detected_device = false;

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_INFO("TWI scanner.\r\n");
    NRF_LOG_FLUSH();
    twi_init();
	if(writeBit()==true)
			{
				NRF_LOG_INFO("No hmc5883l device was found.\r\n");
        NRF_LOG_FLUSH();
			}
    for (address = 1; address <= TWI_ADDRESSES; address++)
    {
        err_code = nrf_drv_twi_rx(&m_twi, address, &sample_data, sizeof(sample_data));
        if (err_code == NRF_SUCCESS)
        {
            detected_device = true;
            NRF_LOG_INFO("TWI device detected at address 0x%x.\r\n", address);
        }
        NRF_LOG_FLUSH();
    }

    if (!detected_device)
    {
        NRF_LOG_INFO("No device was found.\r\n");
        NRF_LOG_FLUSH();
    }

    while (true)
    {
        /* Empty loop. */
    }
}

[FormerMember]

The second parameter of nrf_drv_twi_tx() is address, could you try to replace 0x1E with 0x68 or 0x77?

[omar]

I have tested these adress and they work well but i want to activate in this program the bypass of mpu6050 to detect adress of magnetometer which is 0x1E, the activation of this bypass made by writting one byte into the register 0x37 and then i can detect magnetometer device and we can get magnetic component but i didn't to activate it and I think the problem is in the TWI connection or the TWI command. The major problem is that function worked very well with other device mpu6050 (0x68 0x77)

[MartinBL]

Hi @omar,

I think you are setting the bypass bit wrong. You need to write a '1' to the I2C_BYPASS_EN bit in the INT_PIN_CFG register in the MPU6050, not in the magnetometer. In other words, try something like this:

bool writeBit()
{
        uint8_t packet[2] = {0x37, 2}; // <- WRITE THE VALUE 2 TO REGISTER 0x37
        ret_code_t err_code;
        err_code = nrf_drv_twi_tx(&m_twi,0x68,packet,sizeof(packet),false); // <- USE THE ADDRESS OF THE MPU
        APP_ERROR_CHECK(err_code);

   return err_code;
}

After doing this you should be able to get a response from the magnetometer by using the twi_scanner example in our SDK.

[omar]

I don't now why you put 2 to register 0x37 because in the datasheet, there are just 0 or 1. I tried with 2 but it doesn't work.

[MartinBL]

To set the I2C_BYPASS_EN bit in the register you will need to write the value 2 to the register: Anyway, I think I may have misunderstood you. Is it so that you have three slave devices, one MPU6050, one BME280, and one HMC5883L? But only the first two are responding? How have you connected everything? Why do you need to enable the I2C bypass features in the MPU6050?