Adafruit_I2C.py
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#!/usr/bin/python
import smbus
# ===========================================================================
# Adafruit_I2C Class
# ===========================================================================
class Adafruit_I2C(object):
@staticmethod
def getPiRevision():
"Gets the version number of the Raspberry Pi board"
# Courtesy quick2wire-python-api
# https://github.com/quick2wire/quick2wire-python-api
# Updated revision info from: http://elinux.org/RPi_HardwareHistory#Board_Revision_History
try:
with open('/proc/cpuinfo','r') as f:
for line in f:
if line.startswith('Revision'):
return 1 if line.rstrip()[-1] in ['2','3'] 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, 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 as 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 as 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 as 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 as 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 as 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 as 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 as 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 as 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 as err:
return self.errMsg()
if __name__ == '__main__':
try:
bus = Adafruit_I2C(address=0x60)
print("Default I2C bus is accessible")
except:
print("Error accessing default I2C bus")