一、介绍
MPU9250和MPU9255内部都是集成MPU6515+AK8963两个传感器，接口也是一样兼容都含有I2C和SPI接口。真没看出有什么硬件有什么区别，只有内部固件有一点区别，后者dmp库多了几个功能接口函数，支持如骑行等运动模式检测等。**
MPU9150是只支持I2C的，MPU9250是支持SPI/I2C两种方式。里面的传感器也是不同的，MPU9150里面是MPU6050+AK8975C，而MPU9250里面是MPU6515+AK8963，这两个传感器组合不同，前者性能上要高一些，后者主打低功耗方面的，各种参数要略低一些，比如唤醒速度等。具体请对照数据手册。
使用MPU6050 Yaw轴会不可避免的飘动，MPU9250自带磁力计，可以减少飘动。
二、代码
参考 https://github.com/micropython-IMU/micropython-mpu9x50
# mpu9250.py MicroPython driver for the InvenSense MPU9250 inertial measurement unit
# Authors Peter Hinch, Sebastian Plamauer
# V0.5 17th June 2015
'''
mpu9250 is a micropython module for the InvenSense MPU9250 sensor.
It measures acceleration, turn rate and the magnetic field in three axis.
The MIT License (MIT)
Copyright (c) 2014 Sebastian Plamauer, oeplse@gmail.com, Peter Hinch
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.
'''
from imu import InvenSenseMPU, bytes_toint, MPUException
from imu import Vector3d
class MPU9250(InvenSenseMPU):
'''
MPU9250 constructor arguments
1. side_str 'X' or 'Y' depending on the Pyboard I2C interface being used
2. optional device_addr 0, 1 depending on the voltage applied to pin AD0 (Drotek default is 1)
if None driver will scan for a device (if one device only is on bus)
3, 4. transposition, scaling optional 3-tuples allowing for outputs to be based on vehicle
coordinates rather than those of the sensor itself. See readme.
'''
_mpu_addr = (104, 105) # addresses of MPU9250 determined by voltage on pin AD0
_mag_addr = 12 # Magnetometer address
_chip_id = 113
def __init__(self, side_str, device_addr=None, transposition=(0, 1, 2), scaling=(1, 1, 1)):
super().__init__(side_str, device_addr, transposition, scaling)
self._mag = Vector3d(transposition, scaling, self._mag_callback)
self.accel_filter_range = 0 # fast filtered response
self.gyro_filter_range = 0
self._mag_stale_count = 0 # MPU9250 count of consecutive reads where old data was returned
self.mag_correction = self._magsetup() # 16 bit, 100Hz update.Return correction factors.
self._mag_callback() # Seems neccessary to kick the mag off else 1st reading is zero (?)
@property
def sensors(self):
'''
returns sensor objects accel, gyro and mag
'''
return self._accel, self._gyro, self._mag
# get temperature
@property
def temperature(self):
'''
Returns the temperature in degree C.
'''
try:
self._read(self.buf2, 0x41, self.mpu_addr)
except OSError:
raise MPUException(self._I2Cerror)
return bytes_toint(self.buf2[0], self.buf2[1])/333.87 + 21 # I think
# Low pass filters
@property
def gyro_filter_range(self):
'''
Returns the gyro and temperature sensor low pass filter cutoff frequency
Pass: 0 1 2 3 4 5 6 7
Cutoff (Hz): 250 184 92 41 20 10 5 3600
Sample rate (KHz): 8 1 1 1 1 1 1 8
'''
try:
self._read(self.buf1, 0x1A, self.mpu_addr)
res = self.buf1[0] & 7
except OSError:
raise MPUException(self._I2Cerror)
return res
@gyro_filter_range.setter
def gyro_filter_range(self, filt):
'''
Sets the gyro and temperature sensor low pass filter cutoff frequency
Pass: 0 1 2 3 4 5 6 7
Cutoff (Hz): 250 184 92 41 20 10 5 3600
Sample rate (KHz): 8 1 1 1 1 1 1 8
'''
if filt in range(8):
try:
self._write(filt, 0x1A, self.mpu_addr)
except OSError:
raise MPUException(self._I2Cerror)
else:
raise ValueError('Filter coefficient must be between 0 and 7')
@property
def accel_filter_range(self):
'''
Returns the accel low pass filter cutoff frequency
Pass: 0 1 2 3 4 5 6 7 BEWARE 7 doesn't work on device I tried.
Cutoff (Hz): 460 184 92 41 20 10 5 460
Sample rate (KHz): 1 1 1 1 1 1 1 1
'''
try:
self._read(self.buf1, 0x1D, self.mpu_addr)
res = self.buf1[0] & 7
except OSError:
raise MPUException(self._I2Cerror)
return res
@accel_filter_range.setter
def accel_filter_range(self, filt):
'''
Sets the accel low pass filter cutoff frequency
Pass: 0 1 2 3 4 5 6 7 BEWARE 7 doesn't work on device I tried.
Cutoff (Hz): 460 184 92 41 20 10 5 460
Sample rate (KHz): 1 1 1 1 1 1 1 1
'''
if filt in range(8):
try:
self._write(filt, 0x1D, self.mpu_addr)
except OSError:
raise MPUException(self._I2Cerror)
else:
raise ValueError('Filter coefficient must be between 0 and 7')
def _magsetup(self): # mode 2 100Hz continuous reads, 16 bit
'''
Magnetometer initialisation: use 16 bit continuous mode.
Mode 1 is 8Hz mode 2 is 100Hz repetition
returns correction values
'''
try:
self._write(0x0F, 0x0A, self._mag_addr) # fuse ROM access mode
self._read(self.buf3, 0x10, self._mag_addr) # Correction values
self._write(0, 0x0A, self._mag_addr) # Power down mode (AK8963 manual 6.4.6)
self._write(0x16, 0x0A, self._mag_addr) # 16 bit (0.15uT/LSB not 0.015), mode 2
except OSError:
raise MPUException(self._I2Cerror)
mag_x = (0.5*(self.buf3[0] - 128))/128 + 1
mag_y = (0.5*(self.buf3[1] - 128))/128 + 1
mag_z = (0.5*(self.buf3[2] - 128))/128 + 1
return (mag_x, mag_y, mag_z)
@property
def mag(self):
'''
Magnetomerte object
'''
return self._mag
def _mag_callback(self):
'''
Update magnetometer Vector3d object (if data available)
'''
try: # If read fails, returns last valid data and
self._read(self.buf1, 0x02, self._mag_addr) # increments mag_stale_count
if self.buf1[0] & 1 == 0:
return self._mag # Data not ready: return last value
self._read(self.buf6, 0x03, self._mag_addr)
self._read(self.buf1, 0x09, self._mag_addr)
except OSError:
raise MPUException(self._I2Cerror)
if self.buf1[0] & 0x08 > 0: # An overflow has occurred
self._mag_stale_count += 1 # Error conditions retain last good value
return # user should check for ever increasing stale_counts
self._mag._ivector[1] = bytes_toint(self.buf6[1], self.buf6[0]) # Note axis twiddling and little endian
self._mag._ivector[0] = bytes_toint(self.buf6[3], self.buf6[2])
self._mag._ivector[2] = -bytes_toint(self.buf6[5], self.buf6[4])
scale = 0.15 # scale is 0.15uT/LSB
self._mag._vector[0] = self._mag._ivector[0]*self.mag_correction[0]*scale
self._mag._vector[1] = self._mag._ivector[1]*self.mag_correction[1]*scale
self._mag._vector[2] = self._mag._ivector[2]*self.mag_correction[2]*scale
self._mag_stale_count = 0
@property
def mag_stale_count(self):
'''
Number of consecutive times where old data was returned
'''
return self._mag_stale_count
def get_mag_irq(self):
'''
Uncorrected values because floating point uses heap
'''
self._read(self.buf1, 0x02, self._mag_addr)
if self.buf1[0] == 1: # Data is ready
self._read(self.buf6, 0x03, self._mag_addr)
self._read(self.buf1, 0x09, self._mag_addr) # Mandatory status2 read
self._mag._ivector[1] = 0
if self.buf1[0] & 0x08 == 0: # No overflow has occurred
self._mag._ivector[1] = bytes_toint(self.buf6[1], self.buf6[0])
self._mag._ivector[0] = bytes_toint(self.buf6[3], self.buf6[2])
self._mag._ivector[2] = -bytes_toint(self.buf6[5], self.buf6[4])
