LSM303D.py

#Driver for the LSM303D accelerometer and magnetometer/compass
#First follow the procedure to enable I2C on R-Pi.
#1. Add the lines "ic2-bcm2708" and "i2c-dev" to the file /etc/modules
#2. Comment out the line "blacklist ic2-bcm2708" (with a #) in the file /etc/modprobe.d/raspi-blacklist.conf
#3. Install I2C utility (including smbus) with the command "apt-get install python-smbus i2c-tools"
#4. Connect the I2C device and detect it using the command "i2cdetect -y 1".  It should show up as 1D or 1E (here the variable LSM is set to 1D).
#Driver by Fayetteville Free Library Robotics Group
from smbus import SMBus
busNum = 1
b = SMBus(busNum)
LSM = 0x1d
LSM_WHOAMI = 0b1001001 #Device self-id
def twos_comp_combine(msb, lsb):
    twos_comp = 256*msb + lsb
    if twos_comp >= 32768:
        return twos_comp - 65536
    else:
        return twos_comp
#Control register addresses -- from LSM303D datasheet
CTRL_0 = 0x1F #General settings
CTRL_1 = 0x20 #Turns on accelerometer and configures data rate
CTRL_2 = 0x21 #Self test accelerometer, anti-aliasing accel filter
CTRL_3 = 0x22 #Interrupts
CTRL_4 = 0x23 #Interrupts
CTRL_5 = 0x24 #Turns on temperature sensor
CTRL_6 = 0x25 #Magnetic resolution selection, data rate config
CTRL_7 = 0x26 #Turns on magnetometer and adjusts mode
#Registers holding twos-complemented MSB and LSB of magnetometer readings -- from LSM303D datasheet
MAG_X_LSB = 0x08 # x
MAG_X_MSB = 0x09
MAG_Y_LSB = 0x0A # y
MAG_Y_MSB = 0x0B
MAG_Z_LSB = 0x0C # z
MAG_Z_MSB = 0x0D
#Registers holding twos-complemented MSB and LSB of magnetometer readings -- from LSM303D datasheet
ACC_X_LSB = 0x28 # x
ACC_X_MSB = 0x29
ACC_Y_LSB = 0x2A # y
ACC_Y_MSB = 0x2B
ACC_Z_LSB = 0x2C # z
ACC_Z_MSB = 0x2D
#Registers holding 12-bit right justified, twos-complemented temperature data -- from LSM303D datasheet
TEMP_MSB = 0x05
TEMP_LSB = 0x06
if b.read_byte_data(LSM, 0x0f) == LSM_WHOAMI:
    print 'LSM303D detected successfully.'
else:
    print 'No LSM303D detected on bus '+str(busNum)+'.'
b.write_byte_data(LSM, CTRL_1, 0b1010111) # enable accelerometer, 50 hz sampling
b.write_byte_data(LSM, CTRL_2, 0x00) #set +/- 2g full scale
b.write_byte_data(LSM, CTRL_5, 0b01100100) #high resolution mode, thermometer off, 6.25hz ODR
b.write_byte_data(LSM, CTRL_6, 0b00100000) # set +/- 4 gauss full scale
b.write_byte_data(LSM, CTRL_7, 0x00) #get magnetometer out of low power mode
magx = twos_comp_combine(b.read_byte_data(LSM, MAG_X_MSB), b.read_byte_data(LSM, MAG_X_LSB))
magy = twos_comp_combine(b.read_byte_data(LSM, MAG_Y_MSB), b.read_byte_data(LSM, MAG_Y_LSB))
magz = twos_comp_combine(b.read_byte_data(LSM, MAG_Z_MSB), b.read_byte_data(LSM, MAG_Z_LSB))
print "Magnetic field (x, y, z):", magx, magy, magz
accx = twos_comp_combine(b.read_byte_data(LSM, ACC_X_MSB), b.read_byte_data(LSM, ACC_X_LSB))
accy = twos_comp_combine(b.read_byte_data(LSM, ACC_Y_MSB), b.read_byte_data(LSM, ACC_Y_LSB))
accz = twos_comp_combine(b.read_byte_data(LSM, ACC_Z_MSB), b.read_byte_data(LSM, ACC_Z_LSB))
print "Acceleration (x, y, z):", accx, accy, accz