Initial check in

Adafruit_I2C.py

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+#!/usr/bin/python
+import re
+import smbus
+
+# ===========================================================================
+# Adafruit_I2C Class
+# ===========================================================================
+
+class Adafruit_I2C(object):
+
+  @staticmethod
+  def getPiRevision():
+    "Gets the version number of the Raspberry Pi board"
+    # Revision list available at: http://elinux.org/RPi_HardwareHistory#Board_Revision_History
+    try:
+      with open('/proc/cpuinfo', 'r') as infile:
+        for line in infile:
+          # Match a line of the form "Revision : 0002" while ignoring extra
+          # info in front of the revsion (like 1000 when the Pi was over-volted).
+          match = re.match('Revision\s+:\s+.*(\w{4})$', line)
+          if match and match.group(1) in ['0000', '0002', '0003']:
+            # Return revision 1 if revision ends with 0000, 0002 or 0003.
+            return 1
+          elif match:
+            # Assume revision 2 if revision ends with any other 4 chars.
+            return 2
+        # Couldn't find the revision, assume revision 0 like older code for compatibility.
+        return 0
+    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, busnum=-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(busnum if busnum >= 0 else Adafruit_I2C.getPiI2CBusNumber())
+    self.debug = debug
+
+  def reverseByteOrder(self, data):
+    "Reverses the byte order of an int (16-bit) or long (32-bit) value"
+    # Courtesy Vishal Sapre
+    byteCount = len(hex(data)[2:].replace('L','')[::2])
+    val       = 0
+    for i in range(byteCount):
+      val    = (val << 8) | (data & 0xff)
+      data >>= 8
+    return val
+
+  def errMsg(self):
+    print "Error accessing 0x%02X: Check your I2C address" % self.address
+    return -1
+
+  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:
+      return self.errMsg()
+
+  def write16(self, reg, value):
+    "Writes a 16-bit value to the specified register/address pair"
+    try:
+      self.bus.write_word_data(self.address, reg, value)
+      if self.debug:
+        print ("I2C: Wrote 0x%02X to register pair 0x%02X,0x%02X" %
+         (value, reg, reg+1))
+    except IOError, err:
+      return self.errMsg()
+
+  def writeRaw8(self, value):
+    "Writes an 8-bit value on the bus"
+    try:
+      self.bus.write_byte(self.address, value)
+      if self.debug:
+        print "I2C: Wrote 0x%02X" % value
+    except IOError, err:
+      return self.errMsg()
+
+  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:
+      return self.errMsg()
+
+  def readList(self, reg, length):
+    "Read a list of bytes from the I2C device"
+    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:
+      return self.errMsg()
+
+  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:
+      return self.errMsg()
+
+  def readS8(self, reg):
+    "Reads a signed byte from the I2C device"
+    try:
+      result = self.bus.read_byte_data(self.address, reg)
+      if result > 127: result -= 256
+      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:
+      return self.errMsg()
+
+  def readU16(self, reg, little_endian=True):
+    "Reads an unsigned 16-bit value from the I2C device"
+    try:
+      result = self.bus.read_word_data(self.address,reg)
+      # Swap bytes if using big endian because read_word_data assumes little 
+      # endian on ARM (little endian) systems.
+      if not little_endian:
+        result = ((result << 8) & 0xFF00) + (result >> 8)
+      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:
+      return self.errMsg()
+
+  def readS16(self, reg, little_endian=True):
+    "Reads a signed 16-bit value from the I2C device"
+    try:
+      result = self.readU16(reg,little_endian)
+      if result > 32767: result -= 65536
+      return result
+    except IOError, err:
+      return self.errMsg()
+
+if __name__ == '__main__':
+  try:
+    bus = Adafruit_I2C(address=0)
+    print "Default I2C bus is accessible"
+  except:
+    print "Error accessing default I2C bus"