Added LSM303 library (adapted from Arduino version)

Author: PaintYourDragon

Adafruit_LSM303/Adafruit_I2C.py

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+../Adafruit_I2C/Adafruit_I2C.py

Adafruit_LSM303/Adafruit_LSM303.py

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+#!/usr/bin/python
+
+# Python library for Adafruit Flora Accelerometer/Compass Sensor (LSM303).
+# This is pretty much a direct port of the current Arduino library and is
+# similarly incomplete (e.g. no orientation value returned from read()
+# method).  This does add optional high resolution mode to accelerometer
+# though.
+
+# Copyright 2013 Adafruit Industries
+
+# 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 Adafruit_I2C import Adafruit_I2C
+
+
+class Adafruit_LSM303(Adafruit_I2C):
+
+    # Minimal constants carried over from Arduino library
+    LSM303_ADDRESS_ACCEL = (0x32 >> 1)  # 0011001x
+    LSM303_ADDRESS_MAG   = (0x3C >> 1)  # 0011110x
+                                             # Default    Type
+    LSM303_REGISTER_ACCEL_CTRL_REG1_A = 0x20 # 00000111   rw
+    LSM303_REGISTER_ACCEL_CTRL_REG4_A = 0x23 # 00000000   rw
+    LSM303_REGISTER_ACCEL_OUT_X_L_A   = 0x28
+    LSM303_REGISTER_MAG_CRB_REG_M     = 0x01
+    LSM303_REGISTER_MAG_MR_REG_M      = 0x02
+    LSM303_REGISTER_MAG_OUT_X_H_M     = 0x03
+
+    # Gain settings for setMagGain()
+    LSM303_MAGGAIN_1_3 = 0x20 # +/- 1.3
+    LSM303_MAGGAIN_1_9 = 0x40 # +/- 1.9
+    LSM303_MAGGAIN_2_5 = 0x60 # +/- 2.5
+    LSM303_MAGGAIN_4_0 = 0x80 # +/- 4.0
+    LSM303_MAGGAIN_4_7 = 0xA0 # +/- 4.7
+    LSM303_MAGGAIN_5_6 = 0xC0 # +/- 5.6
+    LSM303_MAGGAIN_8_1 = 0xE0 # +/- 8.1
+
+
+    def __init__(self, busnum=-1, debug=False, hires=False):
+
+        # Accelerometer and magnetometer are at different I2C
+        # addresses, so invoke a separate I2C instance for each
+        self.accel = Adafruit_I2C(self.LSM303_ADDRESS_ACCEL, busnum, debug)
+        self.mag   = Adafruit_I2C(self.LSM303_ADDRESS_MAG  , busnum, debug)
+
+        # Enable the accelerometer
+        self.accel.write8(self.LSM303_REGISTER_ACCEL_CTRL_REG1_A, 0x27)
+        # Select hi-res (12-bit) or low-res (10-bit) output mode.
+        # Low-res mode uses less power and sustains a higher update rate,
+        # output is padded to compatible 12-bit units.
+        if hires:
+            self.accel.write8(self.LSM303_REGISTER_ACCEL_CTRL_REG4_A,
+              0b00001000)
+        else:
+            self.accel.write8(self.LSM303_REGISTER_ACCEL_CTRL_REG4_A, 0)
+  
+        # Enable the magnetometer
+        self.mag.write8(self.LSM303_REGISTER_MAG_MR_REG_M, 0x00)
+
+
+    # Interpret signed 12-bit acceleration component from list
+    def accel12(self, list, idx):
+        n = list[idx] | (list[idx+1] << 8) # Low, high bytes
+        if n > 32767: n -= 65536           # 2's complement signed
+        return n >> 4                      # 12-bit resolution
+
+
+    # Interpret signed 16-bit magnetometer component from list
+    def mag16(self, list, idx):
+        n = (list[idx] << 8) | list[idx+1]   # High, low bytes
+        return n if n < 32768 else n - 65536 # 2's complement signed
+
+
+    def read(self):
+        # Read the accelerometer
+        list = self.accel.readList(
+          self.LSM303_REGISTER_ACCEL_OUT_X_L_A | 0x80, 6)
+        res = [( self.accel12(list, 0),
+                 self.accel12(list, 2),
+                 self.accel12(list, 4) )]
+
+        # Read the magnetometer
+        list = self.mag.readList(self.LSM303_REGISTER_MAG_OUT_X_H_M, 6)
+        res.append((self.mag16(list, 0),
+                    self.mag16(list, 2),
+                    self.mag16(list, 4),
+                    0.0 )) # ToDo: Calculate orientation
+
+        return res
+
+
+    def setMagGain(gain=LSM303_MAGGAIN_1_3):
+        self.mag.write8( LSM303_REGISTER_MAG_CRB_REG_M, gain)
+
+
+# Simple example prints accel/mag data once per second:
+if __name__ == '__main__':
+
+    from time import sleep
+
+    lsm = Adafruit_LSM303()
+
+    print '[(Accelerometer X, Y, Z), (Magnetometer X, Y, Z, orientation)]'
+    while True:
+        print lsm.read()
+        sleep(1) # Output is fun to watch if this is commented out