#!/usr/bin/python3
import re
import smbus


# ===========================================================================
# I2C Class
# ===========================================================================

class MotorI2C(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 MotorI2C.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 MotorI2C.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 IOErro 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:
                

            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 = MotorI2C(address=0)
        print("Default I2C bus is accessible")
    except:
        print("Error accessing default I2C bus")

print("I2C: Device 0x%02X returned 0x%02X from reg 0x%02X" % (self.address, result & 0xFF, reg))