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// MPU-6050 Accelerometer + Gyro
// -----------------------------
//
// By arduino.cc user "Krodal".
// June 2012
// Open Source / Public Domain
//
// Using Arduino 1.0.1
// It will not work with an older version,
// since Wire.endTransmission() uses a parameter
// to hold or release the I2C bus.
//
// Documentation:
// - The InvenSense documents:
// - "MPU-6000 and MPU-6050 Product Specification",
// PS-MPU-6000A.pdf
// - "MPU-6000 and MPU-6050 Register Map and Descriptions",
// RM-MPU-6000A.pdf or RS-MPU-6000A.pdf
// - "MPU-6000/MPU-6050 9-Axis Evaluation Board User Guide"
// AN-MPU-6000EVB.pdf
//
// The accuracy is 16-bits.
//
// Temperature sensor from -40 to +85 degrees Celsius
// 340 per degrees, -512 at 35 degrees.
//
// At power-up, all registers are zero, except these two:
// Register 0x6B (PWR_MGMT_2) = 0x40 (I read zero).
// Register 0x75 (WHO_AM_I) = 0x68.
//
#include <Arduino.h>
#include "MPU6050.h"
// --------------------------------------------------------
// MPU6050_read
//
// This is a common function to read multiple bytes
// from an I2C device.
//
// It uses the boolean parameter for Wire.endTransMission()
// to be able to hold or release the I2C-bus.
// This is implemented in Arduino 1.0.1.
//
// Only this function is used to read.
// There is no function for a single byte.
//
int MPU6050_read(int start, uint8_t *buffer, int size)
{
int i, n;
Wire.beginTransmission(MPU6050_I2C_ADDRESS);
n = Wire.write(start);
if (n != 1)
return (-10);
n = Wire.endTransmission(false); // hold the I2C-bus
if (n != 0)
return (n);
// Third parameter is true: relase I2C-bus after data is read.
Wire.requestFrom(MPU6050_I2C_ADDRESS, size, true);
i = 0;
while(Wire.available() && i<size)
{
buffer[i++]=Wire.read();
}
if ( i != size)
return (-11);
return (0); // return : no error
}
// --------------------------------------------------------
// MPU6050_write
//
// This is a common function to write multiple bytes to an I2C device.
//
// If only a single register is written,
// use the function MPU_6050_write_reg().
//
// Parameters:
// start : Start address, use a define for the register
// pData : A pointer to the data to write.
// size : The number of bytes to write.
//
// If only a single register is written, a pointer
// to the data has to be used, and the size is
// a single byte:
// int data = 0; // the data to write
// MPU6050_write (MPU6050_PWR_MGMT_1, &c, 1);
//
int MPU6050_write(int start, const uint8_t *pData, int size)
{
int n, error;
Wire.beginTransmission(MPU6050_I2C_ADDRESS);
n = Wire.write(start); // write the start address
if (n != 1)
return (-20);
n = Wire.write(pData, size); // write data bytes
if (n != size)
return (-21);
error = Wire.endTransmission(true); // release the I2C-bus
if (error != 0)
return (error);
return (0); // return : no error
}
// --------------------------------------------------------
// MPU6050_write_reg
//
// An extra function to write a single register.
// It is just a wrapper around the MPU_6050_write()
// function, and it is only a convenient function
// to make it easier to write a single register.
//
int MPU6050_write_reg(int reg, uint8_t data)
{
int error;
error = MPU6050_write(reg, &data, 1);
return (error);
}
// --------------------------------------------------------
// MPU6050_init
//
// Initialization
//
int MPU6050_init()
{
// default at power-up:
// Gyro at 250 degrees second
// Acceleration at 2g
// Clock source at internal 8MHz
// The device is in sleep mode.
//
uint8_t c;
int error;
error = MPU6050_read (MPU6050_WHO_AM_I, &c, 1);
if (error) return error;
// According to the datasheet, the 'sleep' bit
// should read a '1'. But I read a '0'.
// That bit has to be cleared, since the sensor
// is in sleep mode at power-up. Even if the
// bit reads '0'.
error = MPU6050_read (MPU6050_PWR_MGMT_2, &c, 1);
if (error) return error;
// Clear the 'sleep' bit to start the sensor.
MPU6050_write_reg (MPU6050_PWR_MGMT_1, 0);
return 0;
}
// --------------------------------------------------------
// MPU6050_readout
//
// Perform an complete read-out
//
int MPU6050_readout(accel_t_gyro_union* accel_t_gyro)
{
int error;
// Read the raw values.
// Read 14 bytes at once,
// containing acceleration, temperature and gyro.
// With the default settings of the MPU-6050,
// there is no filter enabled, and the values
// are not very stable.
error = MPU6050_read (MPU6050_ACCEL_XOUT_H, (uint8_t *)accel_t_gyro, sizeof(accel_t_gyro_union));
if (error) return error;
// Swap all high and low bytes.
// After this, the registers values are swapped,
// so the structure name like x_accel_l does no
// longer contain the lower byte.
uint8_t swap;
#define SWAP(x,y) swap = x; x = y; y = swap
SWAP (accel_t_gyro->reg.x_accel_h, accel_t_gyro->reg.x_accel_l);
SWAP (accel_t_gyro->reg.y_accel_h, accel_t_gyro->reg.y_accel_l);
SWAP (accel_t_gyro->reg.z_accel_h, accel_t_gyro->reg.z_accel_l);
SWAP (accel_t_gyro->reg.t_h, accel_t_gyro->reg.t_l);
SWAP (accel_t_gyro->reg.x_gyro_h, accel_t_gyro->reg.x_gyro_l);
SWAP (accel_t_gyro->reg.y_gyro_h, accel_t_gyro->reg.y_gyro_l);
SWAP (accel_t_gyro->reg.z_gyro_h, accel_t_gyro->reg.z_gyro_l);
return 0;
}
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