Adafruit_I2C.py

#!/usr/bin/python

import smbus

# ===========================================================================
# Adafruit_I2C Base Class
# ===========================================================================

class Adafruit_I2C :

  @staticmethod
  def getPiRevision():
    "Gets the version number of the Raspberry Pi board"
    # Courtesy quick2wire-python-api
    # https://github.com/quick2wire/quick2wire-python-api
    try:
      with open('/proc/cpuinfo','r') as f:
        for line in f:
          if line.startswith('Revision'):
            return 1 if line.rstrip()[-1] in ['1','2'] else 2
    except:
      return 0
  
  @staticmethod
  def getPiI2CBusNumber():
    # Gets the I2C bus number /dev/i2c#
    return 1 if Adafruit_I2C.getPiRevision() > 1 else 0
 
  def __init__(self, address, bus=-1, debug=False):
    self.address = address
    # By default, the correct I2C bus is auto-detected using /proc/cpuinfo
    # Alternatively, you can hard-code the bus version below:
    # self.bus = smbus.SMBus(0); # Force I2C0 (early 256MB Pi's)
    # self.bus = smbus.SMBus(1); # Force I2C1 (512MB Pi's)
    self.bus = smbus.SMBus(Adafruit_I2C.getPiI2CBusNumber() if bus == -1 else bus)
    self.debug = debug

  def reverseByteOrder(self, data):
    "Reverses the byte order of an int (16-bit) or long (32-bit) value"
    # Courtesy Vishal Sapre
    dstr = hex(data)[2:].replace('L','')
    byteCount = len(dstr[::2])
    val = 0
    for i, n in enumerate(range(byteCount)):
      d = data & 0xFF
      val |= (d << (8 * (byteCount - i - 1)))
      data >>= 8
    return val

  def write8(self, reg, value):
    "Writes an 8-bit value to the specified register/address"
    try:
      self.bus.write_byte_data(self.address, reg, value)
      if (self.debug):
        print "I2C: Wrote 0x%02X to register 0x%02X" % (value, reg)
    except IOError, err:
      print "Error accessing 0x%02X: Check your I2C address" % self.address
      return -1

  def writeList(self, reg, list):
    "Writes an array of bytes using I2C format"
    try:
      if (self.debug):
        print "I2C: Writing list to register 0x%02X:" % reg
        print list
      self.bus.write_i2c_block_data(self.address, reg, list)
    except IOError, err:
      print "Error accessing 0x%02X: Check your I2C address" % self.address
      return -1

  def readList(self, reg, length):
    "Read a list of bytes from the I2C device"
    results = []
    try:
      results = self.bus.read_i2c_block_data(self.address, reg, length)
      if (self.debug):
        print "I2C: Device 0x%02X returned the following from reg 0x%02X" % (self.address, reg)
        print results
      return results
    except IOError, err:
      print "Error accessing 0x%02X: Check your I2C address" % self.address
      return -1

  def readU8(self, reg):
    "Read an unsigned byte from the I2C device"
    try:
      result = self.bus.read_byte_data(self.address, reg)
      if (self.debug):
        print "I2C: Device 0x%02X returned 0x%02X from reg 0x%02X" % (self.address, result & 0xFF, reg)
      return result
    except IOError, err:
      print "Error accessing 0x%02X: Check your I2C address" % self.address
      return -1

  def readS8(self, reg):
    "Reads a signed byte from the I2C device"
    try:
      result = self.bus.read_byte_data(self.address, reg)
      if (self.debug):
        print "I2C: Device 0x%02X returned 0x%02X from reg 0x%02X" % (self.address, result & 0xFF, reg)
      if (result > 127):
        return result - 256
      else:
        return result
    except IOError, err:
      print "Error accessing 0x%02X: Check your I2C address" % self.address
      return -1

  def readU16(self, reg):
    "Reads an unsigned 16-bit value from the I2C device"
    try:
      hibyte = self.bus.read_byte_data(self.address, reg)
      result = (hibyte << 8) + self.bus.read_byte_data(self.address, reg+1)
      if (self.debug):
        print "I2C: Device 0x%02X returned 0x%04X from reg 0x%02X" % (self.address, result & 0xFFFF, reg)
      return result
    except IOError, err:
      print "Error accessing 0x%02X: Check your I2C address" % self.address
      return -1

  def readS16(self, reg):
    "Reads a signed 16-bit value from the I2C device"
    try:
      hibyte = self.bus.read_byte_data(self.address, reg)
      if (hibyte > 127):
        hibyte -= 256
      result = (hibyte << 8) + self.bus.read_byte_data(self.address, reg+1)
      if (self.debug):
        print "I2C: Device 0x%02X returned 0x%04X from reg 0x%02X" % (self.address, result & 0xFFFF, reg)
      return result
    except IOError, err:
      print "Error accessing 0x%02X: Check your I2C address" % self.address
      return -1