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import serial

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import exceptions

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import ctypes

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import time

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from threading import Lock

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MAX_PACKET_SIZE=64

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    11

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class LPCError(exceptions.Exception):

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        """Exception class"""

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        def __init__(self, msg):

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                self.msg = msg

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                return

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        def __str__(self):

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                return "LPC communication error ! " + str(self.msg)

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class LPCProto:

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    def __init__(self, port, rate, timeout):

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        # serialize access lock

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        self.TransactionLock = Lock()

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        # open serial port

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#        self.serialPort = serial.Serial( port, rate, timeout = timeout )

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        # Debugging serial stuff

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        self._serialPort = serial.Serial( port, rate, timeout = timeout )

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        class myser:

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            def read(self_,cnt):

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                res = self._serialPort.read(cnt)

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                print "Recv :", map(hex,map(ord,res))

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                return res

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            def write(self_, str):

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                print "Send :", map(hex,map(ord,str))

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                self._serialPort.write(str)

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            def flush(self_):

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                self._serialPort.flush()

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        self.serialPort = myser()

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        # start with empty

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        self.serialPort.flush()

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    def HandleTransaction(self, transaction):

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        self.TransactionLock.acquire()

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        try:

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            transaction.SetPseudoFile(self.serialPort)

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            # send command, wait ack (timeout)

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            transaction.SendCommand()

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            current_plc_status = transaction.GetCommandAck()

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            if current_plc_status is not None:

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                res = transaction.ExchangeData()

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            else:

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                raise LPCError("LPC transaction error - controller did not answer as expected")

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        finally:

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            self.TransactionLock.release()

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class LPCTransaction:

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    def __init__(self, command, optdata = ""):

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        self.Command = command

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        self.OptData = optdata

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        self.pseudofile = None

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    def SetPseudoFile(self, pseudofile):

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        self.pseudofile = pseudofile

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    def SendCommand(self):

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        # send command thread

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        self.pseudofile.write(chr(self.Command))

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    def GetCommandAck(self):

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        res = self.pseudofile.read(2)

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        if len(res) == 2:

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            comm_status, current_plc_status = map(ord, res)

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        else:

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            raise LPCError("LPC transaction error - controller did not ack order")

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        # LPC returns command itself as an ack for command

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        if(comm_status == self.Command):

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            return current_plc_status

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        return None 

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    def SendData(self):

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        length = len(self.OptData)

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        # transform length into a byte string

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        # we presuppose endianess of LPC same as PC

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        lengthstr = ctypes.string_at(ctypes.pointer(ctypes.c_int(length)),4)

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        buffer = lengthstr + self.OptData

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        ###################################################################

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        # TO BE REMOVED AS SOON AS USB IS FIXED IN CONTROLLER

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        ###################################################################

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        length += 4

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        cursor = 0

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        while cursor < length:

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            next_cursor = cursor + MAX_PACKET_SIZE

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            # sent just enough bytes to not crash controller

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            self.pseudofile.write(buffer[cursor:next_cursor])

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            # if sent quantity was 128

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            if next_cursor <= length:

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                self.GetCommandAck()

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            cursor = next_cursor

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    def GetData(self):

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        lengthstr = self.pseudofile.read(4)

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        # transform a byte string into length 

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        length = ctypes.cast(ctypes.c_char_p(lengthstr), ctypes.POINTER(ctypes.c_int)).contents.value

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        return self.pseudofile.read(length)

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    def ExchangeData(self): 

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        pass

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class IDLETransaction(LPCTransaction):

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    def __init__(self):

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        LPCTransaction.__init__(self, 0x00)

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class STARTTransaction(LPCTransaction):

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    def __init__(self):

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        LPCTransaction.__init__(self, 0x01)

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class STOPTransaction(LPCTransaction):

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    def __init__(self):

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        LPCTransaction.__init__(self, 0x02)

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class SET_TRACE_VARIABLETransaction(LPCTransaction):

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    def __init__(self, data):

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        LPCTransaction.__init__(self, 0x04, data)

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    ExchangeData = LPCTransaction.SendData

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class GET_TRACE_VARIABLETransaction(LPCTransaction):

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    def __init__(self):

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        LPCTransaction.__init__(self, 0x05)

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    ExchangeData = LPCTransaction.GetData

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class GET_PLCIDTransaction(LPCTransaction):

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    def __init__(self):

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        LPCTransaction.__init__(self, 0x07)

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    ExchangeData = LPCTransaction.GetData

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if __name__ == "__main__":

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    TestConnection = LPCProto(6,115200,2)

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#    TestConnection.HandleTransaction(GET_PLCIDTransaction())

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    TestConnection.HandleTransaction(STARTTransaction())

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#    TestConnection.HandleTransaction(SET_TRACE_VARIABLETransaction(

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#           "\x03\x00\x00\x00"*200))

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#    TestConnection.HandleTransaction(STARTTransaction())

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    #status,res = TestConnection.HandleTransaction(GET_TRACE_VARIABLETransaction())

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    #print len(res)

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    #print "GOT : ", map(hex, map(ord, res))

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    #TestConnection.HandleTransaction(STOPTransaction())