mpu6050.py

'''
mpu6050 is a micropython module for the InvenSense MPU6050 sensor.
It measures acceleration, turn rate, in three axis.

modified from turbinenreiter/mpu9150

The MIT License (MIT)
Copyright (c) 2014 Sebastian Plamauer, oeplse@gmail.com
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

'''

import pyb
import os
from struct import unpack as unp
from math import atan2,degrees,pi


class MPU6050():
    '''
    Module for the MPY6050 6DOF IMU. 
    By default interrupts are disabled while reading or writing to the device. This
    prevents occasional bus lockups in the presence of pin interrupts, at the cost
    of disabling interrupts for about 250uS.
    '''

    mpu_addr = 0x68  # address of MPU6050
    _I2Cerror = "I2C communication failure"
    
    def __init__(self, side=1, disable_interrupts=False):

        # create i2c object
        self._timeout = 10
        self.disable_interrupts = False
        self._mpu_i2c = pyb.I2C(side, pyb.I2C.MASTER)
        self.chip_id = int(unp('>h', self._read(1, 0x75, self.mpu_addr))[0])

        # now apply user setting for interrupts
        self.disable_interrupts = disable_interrupts

        # wake it up
        self.wake()
        self.accel_range(1)
        self._ar = self.accel_range()
        self.gyro_range(0)
        self._gr = self.gyro_range()

    # read from device
    def _read(self, count, memaddr, devaddr):
        '''
        Perform a memory read. Caller should trap OSError. Possible values of
        error args[0]: errorno.ETIMEDOUT errno.EBUSY or errno.EIO
        '''
        irq_state = True
        if self.disable_interrupts:
            irq_state = pyb.disable_irq()
        result = self._mpu_i2c.mem_read(count,
                                        devaddr,
                                        memaddr,
                                        timeout=self._timeout)
        pyb.enable_irq(irq_state)
        return result

    # write to device
    def _write(self, data, memaddr, devaddr):
        '''
        Perform a memory write. Caller should trap OSError.
        '''
        irq_state = True
        if self.disable_interrupts:
            irq_state = pyb.disable_irq()
        result = self._mpu_i2c.mem_write(data,
                                         devaddr,
                                         memaddr,
                                         timeout=self._timeout)
        pyb.enable_irq(irq_state)
        return result

    # wake
    def wake(self):
        '''
        Wakes the device.
        '''
        try:
            self._write(0x01, 0x6B, self.mpu_addr)
        except OSError:
            print(MPU6050._I2Cerror)
        return 'awake'

    # mode
    def sleep(self):
        '''
        Sets the device to sleep mode.
        '''
        try:
            self._write(0x40, 0x6B, self.mpu_addr)
        except OSError:
            print(MPU6050._I2Cerror)
        return 'asleep'

 
    # sample rate
    def sample_rate(self, rate=None):
        '''
        Returns the sample rate or sets it to the passed arg in Hz. Note that
        not all sample rates are possible. Check the return value to see which
        rate was actually set.
        '''

        gyro_rate = 8000 # Hz

        # set rate
        try:
            if rate is not None:
                rate_div = int( gyro_rate/rate - 1 )
                if rate_div > 255:
                    rate_div = 255
                self._write(rate_div, 0x19, self.mpu_addr)

            # get rate
            rate = gyro_rate/(unp('<H', self._read(1, 0x19, self.mpu_addr))[0]+1)
        except OSError:
            rate = None
        return rate

    # accelerometer range
    def accel_range(self, accel_range=None):
        '''
        Returns the accelerometer range or sets it to the passed arg.
        Pass:               0   1   2   3
        for range +/-:      2   4   8   16  g 
        '''
        # set range
        try:
            if accel_range is None:
                pass
            else:
                ar = (0x00, 0x08, 0x10, 0x18)
                try:
                    self._write(ar[accel_range], 0x1C, self.mpu_addr)
                except IndexError:
                    print('accel_range can only be 0, 1, 2 or 3')
            # get range
            ari = int(unp('<H', self._read(1, 0x1C, self.mpu_addr))[0]/8)
        except OSError:
            ari = None
        if ari is not None:
            self._ar = ari
        return ari

    # gyroscope range
    def gyro_range(self, gyro_range=None):
        '''
        Returns the gyroscope range or sets it to the passed arg.
        Pass:               0   1   2    3
        for range +/-:      250 500 1000 2000  degrees/second
        '''
        # set range
        try:
            if gyro_range is None:
                pass
            else:
                gr = (0x00, 0x08, 0x10, 0x18)
                try:
                    self._write(gr[gyro_range], 0x1B, self.mpu_addr)
                except IndexError:
                    print('gyro_range can only be 0, 1, 2 or 3')
            # get range
            gri = int(unp('<H', self._read(1, 0x1B, self.mpu_addr))[0]/8)
        except OSError:
            gri = None

        if gri is not None:
            self._gr = gri
        return gri

    # get raw acceleration
    def get_accel_raw(self):
        '''
        Returns the accelerations on xyz in bytes.
        '''
        try:
            axyz = self._read(6, 0x3B, self.mpu_addr)
        except OSError:
            axyz = b'\x00\x00\x00\x00\x00\x00'
        return axyz


    # get acceleration
    def get_acc(self, xyz=None):
        '''
        Returns the accelerations on axis passed in arg. Pass xyz or every 
        subset of this string. None defaults to xyz.
        '''
        if xyz is None:
            xyz = 'xyz'
        scale = (16384, 8192, 4096, 2048)
        raw = self.get_accel_raw()
        axyz = {'x': unp('>h', raw[0:2])[0]/scale[self._ar],
                'y': unp('>h', raw[2:4])[0]/scale[self._ar],
                'z': unp('>h', raw[4:6])[0]/scale[self._ar]}

        aout = []
        for char in xyz:
            aout.append(axyz[char])
        return aout

    # get pitch  
    def pitch(self):
        '''
        Returns pitch angle in degrees based on x and c accelerations.
        
        '''
        scale = (16384, 8192, 4096, 2048)
        raw = self.get_accel_raw()
        x = unp('>h', raw[0:2])[0]/scale[self._ar]
        z = unp('>h', raw[4:6])[0]/scale[self._ar]
        pitch = degrees(pi+atan2(-x,-z))
        if (pitch>=180) and (pitch<=360):
            pitch-=360
        return -pitch

    # get raw gyro
    def get_gyro_raw(self):
        '''
        Returns the turn rate on xyz in bytes.
        '''
        try:
            gxyz = self._read(6, 0x43, self.mpu_addr)
        except OSError:
            gxyz = b'\x00\x00\x00\x00\x00\x00'
        return gxyz

    # get gyro
    def get_gyro(self, xyz=None, use_radians=False):
        '''
        Returns the turn rate on axis passed in arg in deg/s or rad/s,
        defaulting to degrees. Pass xyz or every 
        subset of this string. None defaults to xyz.
        '''
        if xyz is None:
            xyz = 'xyz'
        if use_radians:
            scale = (7150, 3755, 1877.5, 938.75)
        else:
            scale = (131.0, 65.5, 32.8, 16.4)
        raw = self.get_gyro_raw()
        gxyz = {'x': unp('>h', raw[0:2])[0]/scale[self._gr],
                'y': unp('>h', raw[2:4])[0]/scale[self._gr],
                'z': unp('>h', raw[4:6])[0]/scale[self._gr]}

        gout = []
        for char in xyz:
            gout.append(gxyz[char])
        return gout

    # get gyro pitch - y - axis in degrees
    def get_gy(self):
        scale = (131.0, 65.5, 32.8, 16.4)
        raw = self.get_gyro_raw()
        gy =  unp('>h', raw[2:4])[0]/scale[self._gr]
        return gy