MPU6050 with STM32 reading axes X,Y,Z values problems

Question

I have an STM32F303 Discovery and I want to use the I2C bus to receive the x,y,z data from an accelerometer MPU6050. Does anyone have source code for this? The problem is that the address of the buffers (i2cBuff) are 0, and the Xaccel, Yaccel, Zaccel too.

Here is my code:

#include "main.h"
#include "stm32f3xx_hal.h"

/* Private variables-----*/
I2C_HandleTypeDef hi2c1;
uint8_t i;
uint8_t i2cBuff[8];
uint16_t ax,ay,az;
float Xaccel,Yaccel,Zaccel;

#define mpu6050Address 0xD0


int main(void)
{
   HAL_Init();
   /* Configure the system clock */

   /* USER CODE BEGIN 2 */
   for(uint8_t i=0 ; i <255;i++)
   {
       if(HAL_I2C_IsDeviceReady(&hi2c1,i,1 ,10) == HAL_OK )
       {
          HAL_GPIO_TogglePin(GPIOD, GPIO_PIN_12);
          break;
       }
    }


    /* USER CODE END 2 */

    /* Infinite loop */
    /* USER CODE BEGIN WHILE */
    while (1)
    {

       HAL_I2C_Mem_Read(&hi2c1, mpu6050Address, 0x3B, I2C_MEMADD_SIZE_8BIT, &i2cBuff[1], 6, 10);



       ax = -(i2cBuff[1]<<8 | i2cBuff[2]);
       ay = -(i2cBuff[3]<<8 | i2cBuff[4]);
       az = -(i2cBuff[5]<<8 | i2cBuff[6]);

       Xaccel = ax/8192.0;
       Yaccel = ay/8192.0;
       Zaccel = az/8192.0;
      /* USER CODE END WHILE */

      /* USER CODE BEGIN 3 */

      }
      /* USER CODE END 3 */

   }

Answer 1

I had the same problem and I just fix it by increasing the timeout in Read() operations. Try with this:

HAL_I2C_Mem_Read(&hi2c1, mpu6050Address, 0x3B, I2C_MEMADD_SIZE_8BIT, &i2cBuff[1], 6, 100);

Answer 2

I struggled getting values out of my DMU5060's as well, the device is (or should be?) initialized by writing a zero to the wake up bit or more generally, most examples zero fill the whole power management register at address 0x6B. However, the device kept returning all zeroes on the output data registers, and reading back the power register came back as 0x40, the reset flag was still high.

The solution that ended up working for me was first writing all ones (0xFF) to the power management register, and then writing the all zeroes after. The device operated as expected after.

#define MPU6050_ADDR 0xD0
#define PWR_MGMT_1_REG 0x6B
const uint16_t i2c_timeout = 100;
uint8_t Data;
//---------
Data = 0xFF;
HAL_I2C_Mem_Write(I2Cx, MPU6050_ADDR, PWR_MGMT_1_REG, 1, &Data, 1, i2c_timeout);
Data = 0x00;
HAL_I2C_Mem_Write(I2Cx, MPU6050_ADDR, PWR_MGMT_1_REG, 1, &Data, 1, i2c_timeout);
//---------

I expect it'd work fine with other values too, anything from 0xC0 and up should set the right bit.

The rest of the code is as used in this library: https://github.com/leech001/MPU6050

There is some more to the initialization so might be worth having a look.

(And I'll put in a request to add the above line to the code there too.)

Answer 3

Reading examples elsewhere this program appears to be missing the initial "wake up" signal.

There's an example at https://playground.arduino.cc/Main/MPU-6050#short

This starts by setting register 0x6B to zero. Apparently this is the power management register, and since the device starts up in sleep mode it is required before the device will return results.