How to add driver to Nuttx

1. add configure variables for MPU6050

MPU6050 uses I2C interface to commniucate to with MCU, so we need define two variables for MPU6050 in the configure process.

CONFIG_I2C: using for MPU6050 I2C interface

CONFIG_MPU6050: using for compile

2.add borad support

nuttx-configs\/stm32f429discovery\/src\/stm32_mpu6050.c

/************************************************************************************
 * Name: stm32_mpu6050_initialize
 * Description:
 * Initialize and register the MPU6050 Pressure Sensor driver.
 ************************************************************************************/
int stm32_mpu6050_initialize(FAR const char *devpath)
{
 FAR struct i2c_master_s *i2c;
 int ret;
 i2c = stm32_i2cbus_initialize(MPU6050_I2C_PORTNO); /* Initialize I2C */
 if (!i2c)
 {
  return -ENODEV;
 }
 ret = mpu605_register(devpath, i2c); /* register the mpu6050 sensor */
 if(ret < 0)
 {
  snerr("ERROR: Error registering MPU6050\n");
 }  
 return ret;
}

3.define mpu6050 device's private data

struct mpu6050_dev_s
{
 FAR struct i2c_master_s *i2c;
 uint8_t addr; /* MPU6050 I2C address */
 int freq; /* MPU6050 Frequency <= 4KHz */
 float acc_x; /* accelerometer x axis */
 float acc_y; /* accelerometer y axis */
 float acc_z; /* accelerometer z axis */
 float gy_x; /* gyroscope x axis */
 float gy_y; /* gyroscope y axis */
 float gy_z; /* gyroscope z axis */
};

4.mpu6050 private function

/**************************************************************************** 
* Private Function Prototypes 
****************************************************************************/
static uint8_t mpu6050_getreg8 (FAR struct mpu6050_dev_s *priv, uint8_t regaddr);
static uint16_t mpu6050_getreg16(FAR struct mpu6050_dev_s *priv, uint8_t regaddr);
static void mpu6050_putreg8 (FAR struct mpu6050_dev_s *priv, uint8_t regaddr, uint8_t regval);
static void mpu6050_set_clock_source(FAR struct mpu6050_dev_s *priv, uint8_t source);
static void mpu6050_set_full_scale_gyro_range(FAR struct mpu6050_dev_s *priv, uint8_t range);
static void mpu6050_set_full_scale_accel_range(FAR struct mpu6050_dev_s *priv, uint8_t range);
static void mpu6050_set_sleep_enabled(FAR struct mpu6050_dev_s *priv, uint8_t enabled);
static uint8_t mpu6050_get_device_id(FAR struct mpu6050_dev_s *priv);
static void mpu6050_set_i2c_master_mode_enabled(FAR struct mpu6050_dev_s *priv, uint8_t enabled);
static void mpu6050_set_i2c_bypass_enabled(FAR struct mpu6050_dev_s *priv, uint8_t enabled);
static void mpu6050_initialize(FAR struct mpu6050_dev_s *priv);
static uint8_t mpu6050_is_rdy(void);
static void mpu6050_get_motion(FAR struct mpu6050_dev_s *priv);
static void mpu6050_init_gyro_Offset(void);
static void mpu6050_interrupt_config(FAR struct mpu6050_dev_s *priv);
static void mpu6050_write_bits(FAR struct mpu6050_dev_s *priv, uint8_t regaddr, uint8_t bit_start, uint8_t len, uint8_t data);
static void mpu6050_write_bit(FAR struct mpu6050_dev_s *priv, uint8_t regaddr, uint8_t bit_num, uint8_t data);

5.character driver methods for file system

/* Character driver methods */
static int mpu6050_open (FAR struct file *filep);
static int mpu6050_close(FAR struct file *filep);
static ssize_t mpu6050_read (FAR struct file *filep, FAR char *buffer, size_t buflen);
static ssize_t mpu6050_write(FAR struct file *filep, FAR const char *buffer, size_t buflen);

/**************************************************************************** 
* Private Data 
****************************************************************************/
static const struct file_operations g_mpu6050fops ={ 
mpu6050_open, /* open */ 
mpu6050_close, /* close */ 
mpu6050_read, /* read */ 
mpu6050_write, /* write */
 0, /* seek */
 0, /* ioctl */
#ifndef CONFIG_DISABLE_POLL 0, /* poll */
#endif 
0 /* unlink */
};