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mpu9250_i2c.py
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mpu9250_i2c.py
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#########################################
# Copyright (c) 2020 Maker Portal LLC
# Author: Joshua Hrisko
#########################################
#
# This code handles the smbus
# communications between the RPi and the
# MPU9250 IMU. For testing the MPU9250
# see: imu_test.py
#
#########################################
#
import smbus,time
def MPU6050_start():
# reset all sensors
bus.write_byte_data(MPU6050_ADDR,PWR_MGMT_1,0x80)
time.sleep(0.1)
bus.write_byte_data(MPU6050_ADDR,PWR_MGMT_1,0x00)
time.sleep(0.1)
# power management and crystal settings
bus.write_byte_data(MPU6050_ADDR, PWR_MGMT_1, 0x01)
time.sleep(0.1)
# alter sample rate (stability)
samp_rate_div = 0 # sample rate = 8 kHz/(1+samp_rate_div)
bus.write_byte_data(MPU6050_ADDR, SMPLRT_DIV, samp_rate_div)
time.sleep(0.1)
#Write to Configuration register
bus.write_byte_data(MPU6050_ADDR, CONFIG, 0)
time.sleep(0.1)
#Write to Gyro configuration register
gyro_config_sel = [0b00000,0b01000,0b10000,0b11000] # byte registers
gyro_config_vals = [250.0,500.0,1000.0,2000.0] # degrees/sec
gyro_indx = 0
bus.write_byte_data(MPU6050_ADDR, GYRO_CONFIG, int(gyro_config_sel[gyro_indx]))
time.sleep(0.1)
#Write to Accel configuration register
accel_config_sel = [0b00000,0b01000,0b10000,0b11000] # byte registers
accel_config_vals = [2.0,4.0,8.0,16.0] # g (g = 9.81 m/s^2)
accel_indx = 0
bus.write_byte_data(MPU6050_ADDR, ACCEL_CONFIG, int(accel_config_sel[accel_indx]))
time.sleep(0.1)
# interrupt register (related to overflow of data [FIFO])
bus.write_byte_data(MPU6050_ADDR,INT_PIN_CFG,0x22)
time.sleep(0.1)
# enable the AK8963 magnetometer in pass-through mode
bus.write_byte_data(MPU6050_ADDR, INT_ENABLE, 1)
time.sleep(0.1)
return gyro_config_vals[gyro_indx],accel_config_vals[accel_indx]
def read_raw_bits(register):
# read accel and gyro values
high = bus.read_byte_data(MPU6050_ADDR, register)
low = bus.read_byte_data(MPU6050_ADDR, register+1)
# combine higha and low for unsigned bit value
value = ((high << 8) | low)
# convert to +- value
if(value > 32768):
value -= 65536
return value
def mpu6050_conv():
# raw acceleration bits
acc_x = read_raw_bits(ACCEL_XOUT_H)
acc_y = read_raw_bits(ACCEL_YOUT_H)
acc_z = read_raw_bits(ACCEL_ZOUT_H)
# raw gyroscope bits
gyro_x = read_raw_bits(GYRO_XOUT_H)
gyro_y = read_raw_bits(GYRO_YOUT_H)
gyro_z = read_raw_bits(GYRO_ZOUT_H)
#convert to acceleration in g and gyro dps
a_x = (acc_x/(2.0**15.0))*accel_sens
a_y = (acc_y/(2.0**15.0))*accel_sens
a_z = (acc_z/(2.0**15.0))*accel_sens
w_x = (gyro_x/(2.0**15.0))*gyro_sens
w_y = (gyro_y/(2.0**15.0))*gyro_sens
w_z = (gyro_z/(2.0**15.0))*gyro_sens
return a_x,a_y,a_z,w_x,w_y,w_z
def AK8963_start():
bus.write_byte_data(AK8963_ADDR,AK8963_CNTL,0x00)
time.sleep(0.1)
bus.write_byte_data(AK8963_ADDR,AK8963_CNTL,0x0F)
time.sleep(0.1)
coeff_data = bus.read_i2c_block_data(AK8963_ADDR,AK8963_ASAX,3)
AK8963_coeffx = (0.5*(coeff_data[0]-128)) / 256.0 + 1.0
AK8963_coeffy = (0.5*(coeff_data[1]-128)) / 256.0 + 1.0
AK8963_coeffz = (0.5*(coeff_data[2]-128)) / 256.0 + 1.0
time.sleep(0.1)
bus.write_byte_data(AK8963_ADDR,AK8963_CNTL,0x00)
time.sleep(0.1)
AK8963_bit_res = 0b0001 # 0b0001 = 16-bit
AK8963_samp_rate = 0b0110 # 0b0010 = 8 Hz, 0b0110 = 100 Hz
AK8963_mode = (AK8963_bit_res <<4)+AK8963_samp_rate # bit conversion
bus.write_byte_data(AK8963_ADDR,AK8963_CNTL,AK8963_mode)
time.sleep(0.1)
return [AK8963_coeffx,AK8963_coeffy,AK8963_coeffz]
def AK8963_reader(register):
# read magnetometer values
low = bus.read_byte_data(AK8963_ADDR, register-1)
high = bus.read_byte_data(AK8963_ADDR, register)
# combine higha and low for unsigned bit value
value = ((high << 8) | low)
# convert to +- value
if(value > 32768):
value -= 65536
return value
def AK8963_conv():
# raw magnetometer bits
while 1:
## if ((bus.read_byte_data(AK8963_ADDR,AK8963_ST1) & 0x01))!=1:
## return 0,0,0
mag_x = AK8963_reader(HXH)
mag_y = AK8963_reader(HYH)
mag_z = AK8963_reader(HZH)
# the next line is needed for AK8963
if (bus.read_byte_data(AK8963_ADDR,AK8963_ST2)) & 0x08!=0x08:
break
#convert to acceleration in g and gyro dps
## m_x = AK8963_coeffs[0]*(mag_x/(2.0**15.0))*mag_sens
## m_y = AK8963_coeffs[1]*(mag_y/(2.0**15.0))*mag_sens
## m_z = AK8963_coeffs[2]*(mag_z/(2.0**15.0))*mag_sens
m_x = (mag_x/(2.0**15.0))*mag_sens
m_y = (mag_y/(2.0**15.0))*mag_sens
m_z = (mag_z/(2.0**15.0))*mag_sens
return m_x,m_y,m_z
# MPU6050 Registers
MPU6050_ADDR = 0x68
PWR_MGMT_1 = 0x6B
SMPLRT_DIV = 0x19
CONFIG = 0x1A
GYRO_CONFIG = 0x1B
ACCEL_CONFIG = 0x1C
INT_PIN_CFG = 0x37
INT_ENABLE = 0x38
ACCEL_XOUT_H = 0x3B
ACCEL_YOUT_H = 0x3D
ACCEL_ZOUT_H = 0x3F
TEMP_OUT_H = 0x41
GYRO_XOUT_H = 0x43
GYRO_YOUT_H = 0x45
GYRO_ZOUT_H = 0x47
#AK8963 registers
AK8963_ADDR = 0x0C
AK8963_ST1 = 0x02
HXH = 0x04
HYH = 0x06
HZH = 0x08
AK8963_ST1 = 0x02
AK8963_ST2 = 0x09
AK8963_CNTL = 0x0A
AK8963_ASAX = 0x10
mag_sens = 4800.0 # magnetometer sensitivity: 4800 uT
# start I2C driver
bus = smbus.SMBus(1) # start comm with i2c bus
time.sleep(0.1)
gyro_sens,accel_sens = MPU6050_start() # instantiate gyro/accel
time.sleep(0.1)
AK8963_coeffs = AK8963_start() # instantiate magnetometer
time.sleep(0.1)