60. Exploring the Pi B+'s Ports VI - Controlling Servos Using the MPU-6050

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Hopefully I'm getting a bit closer to a self-balancing platform.  The stage I'm at now effectively has the accelerometer signal being sent to the 2 servos, rotation of the MPU-6050 about its x-axis, rotating one servo, and rotation about the y-axis controlling the second servo.

Here's the code:

	#!/usr/bin/python
	# KC6050Servos.py Reads MPU6050 and also drives 2 servos
	# Initially written by Adafruit and developed by S&S Dec 2014
	import smbus
	import math
	import time
	from Adafruit_PWM_Servo_Driver import PWM
	# Initialise the PWM device using the default address
	pwm = PWM(0x40)
	# Note if you'd like more debug output you can instead run:
	#pwm = PWM(0x40, debug=True)
	servoMin = 150 # Min pulse length out of 4096
	servoMax = 600 # Max pulse length out of 4096
	# Power management registers
	power_mgmt_1 = 0x6b
	power_mgmt_2 = 0x6c
	def read_byte(adr):
	return bus.read_byte_data(address, adr)
	def read_word(adr):
	high = bus.read_byte_data(address, adr)
	low = bus.read_byte_data(address, adr+1)
	val = (high << 8) + low
	return val
	def read_word_2c(adr):
	val = read_word(adr)
	if (val >= 0x8000):
	return -((65535 - val) + 1)
	else:
	return val
	def dist(a,b):
	return math.sqrt((a*a)+(b*b))
	def get_y_rotation(x,y,z):
	radians = math.atan2(x, dist(y,z))
	return -math.degrees(radians)
	def get_x_rotation(x,y,z):
	radians = math.atan2(y, dist(x,z))
	return math.degrees(radians)
	def setServoPulse(channel, pulse):
	pulseLength = 1000000 # 1,000,000 us per second
	pulseLength /= 60 # 60 Hz
	print "%d us per period" % pulseLength
	pulseLength /= 4096 # 12 bits of resolution
	print "%d us per bit" % pulseLength
	pulse *= 1000
	pulse /= pulseLength
	pwm.setPWM(channel, 0, pulse)
	xrot = 0.0
	yrot = 0.0
	def read_data():
	global xrot
	global yrot
	gyro_xout = read_word_2c(0x43)
	gyro_yout = read_word_2c(0x45)
	gyro_zout = read_word_2c(0x47)
	accel_xout = read_word_2c(0x3b)
	accel_yout = read_word_2c(0x3d)
	accel_zout = read_word_2c(0x3f)
	accel_xout_scaled = accel_xout / 16384.0
	accel_yout_scaled = accel_yout / 16384.0
	accel_zout_scaled = accel_zout / 16384.0
	xrot = get_x_rotation(accel_xout_scaled, accel_yout_scaled, accel_zout_scaled)
	yrot = get_y_rotation(accel_xout_scaled, accel_yout_scaled, accel_zout_scaled)
	# print "x-rotation: %.1f" %xrot+" degrees. y-rotation: %.1f" %yrot+" degrees"
	pwm.setPWMFreq(60) # Set frequency to 60 Hz
	bus = smbus.SMBus(1) # or bus = smbus.SMBus(1) for Revision 2 boards
	address = 0x68 # This is the address value read via the i2cdetect command
	# Now wake the 6050 up as it starts in sleep mode
	bus.write_byte_data(address, power_mgmt_1, 0)
	# Map servo rotation to MPU6050 orientation
	slope = (servoMax-servoMin)/90
	middle = servoMin+(servoMax-servoMin)/2
	pwm.setPWM(11, 0, middle)
	pwm.setPWM(15, 0, middle)
	while (True):
	servoPosx = middle+int(slope*xrot)
	servoPosy = middle+int(slope*yrot)
	read_data()
	pwm.setPWM(15, 0, servoPosx)
	pwm.setPWM(11, 0, servoPosy)

view raw KC6050ServoB.py hosted with ❤ by GitHub

Here's the video:

The sensitivity can be changed by adjusting the code