I2C DMA

/* Private variables ---------------------------------------------------------*/
I2C_HandleTypeDef hi2c1;
DMA_HandleTypeDef hdma_i2c1_rx;

/* Private function prototypes -----------------------------------------------*/
static void MX_I2C1_Init(void);

/* I2C1 init function */
static void MX_I2C1_Init(void)
{

  hi2c1.Instance = I2C1;
  hi2c1.Init.ClockSpeed = 400000;
  hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c1.Init.OwnAddress1 = 0;
  hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c1.Init.OwnAddress2 = 0;
  hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

static void MX_DMA_Init(void)
{
  /* DMA controller clock enable */
  __HAL_RCC_DMA1_CLK_ENABLE();

  /* DMA interrupt init */
  /* DMA1_Channel3_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA1_Channel3_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Channel3_IRQn);
  /* DMA1_Channel4_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA1_Channel4_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Channel4_IRQn);
  /* DMA1_Channel7_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA1_Channel7_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Channel7_IRQn);

}


/* Function to read I2C bus */
void readAccelRegisters(void) {
    buffer[0] = 0x3B; // Access register 3B - Accelerometer start of data
    HAL_I2C_Master_Transmit_DMA(&hi2c1, 0x68<<1, buffer, 1);
    HAL_I2C_Master_Receive_DMA(&hi2c1, 0x68<<1, buffer, 6);

    // Bit shift and store each returned byte into variables
    accelX = buffer[0] << 8 | buffer[1]; // Accelerometer X raw
    accelY = buffer[2] << 8 | buffer[3]; // Accelerometer Y raw
    accelZ = buffer[4] << 8 | buffer[5]; // Accelerometer Z raw
}