ed@448: import serial
ed@448: from threading import Lock
ed@448: 
ed@448: LPC_CMDS=dict(IDLE = 0x00,
ed@448:               START = 0x01,
ed@448:               STOP = 0x02,
ed@448:               SET_TRACE_VARIABLE = 0x04,
ed@448:               GET_TRACE_VARIABLES = 0x05,
ed@448:               SET_FORCED_VARIABLE = 0x06,
ed@448:               GET_PLCID = 0x07)
ed@448: 
ed@448: WAIT_DATA = 0x04
ed@448: 
ed@448: LPC_STATUS=dict(STARTED = 0x01,
ed@448:                 STOPPED = 0x02,
ed@448:                 DEBUG = 0x03)
ed@448: 
ed@448: class LPCError(exceptions.Exception):
ed@448:         """Exception class"""
ed@448:         def __init__(self, msg):
ed@448:                 self.msg = msg
ed@448:                 return
ed@448: 
ed@448:         def __str__(self):
ed@448:                 return "LPC communication error ! " + str(self.msg)
ed@448: 
ed@448: class LPCProto:
ed@448:     def __init__(self, port, rate, timeout):
ed@448:         # open serial port
ed@448:         self.serialPort = serial.Serial( port, rate, timeout = timeout )
ed@448:         self.serialPort.flush()
ed@448:         # handshake
ed@448:         self.HandleTransaction(LPCTransaction("IDLE"))
ed@448:         # serialize access lock
ed@448:         self.TransactionLock = Lock()
ed@448:     
ed@448:     def HandleTransaction(self, transaction):
ed@448:         self.TransactionLock.acquire()
ed@448:         try:
ed@448:             transaction.SetPseudoFile(self.serialPort)
ed@448:             # send command, wait ack (timeout)
ed@448:             transaction.SendCommand()
ed@448:             current_plc_status = transaction.GetCommandAck()
ed@448:             if current_plc_status is not None:
ed@448:                 res = transaction.ExchangeData()
ed@448:             else:
ed@448:                 raise LPCError("LPC transaction error - controller did not answer as expected")
ed@448:         finally:
ed@448:             self.TransactionLock.release()
ed@448:         return current_plc_status, res
ed@448:     
ed@448: class LPCTransaction:
ed@448:     def __init__(self, command, optdata):
ed@448:         self.Command =  LPC_CMDS[command]
ed@448:         self.OptData = optdata[:]
ed@448:         self.serialPort = None
ed@448:         
ed@448:     def SetPseudoFile(pseudofile):
ed@448:         self.pseudofile = pseudofile
ed@448:         
ed@448:     def SendCommand(self):
ed@448:         # send command thread
ed@448:         self.pseudofile.write(chr(self.Command))
ed@448:         
ed@448:     def GetCommandAck(self):
ed@448:         comm_status, current_plc_status = map(ord, self.pseudofile.read(2))
ed@448:         # LPC returns command itself as an ack for command
ed@448:         if(comm_status == self.Command):
ed@448:             return current_plc_status
ed@448:         return None 
ed@448:         
ed@448:     def ExchangeData(self):
ed@448:         if self.Command & WAIT_DATA :
ed@448:             length = len(self.OptData)
ed@448:             # transform length into a byte string
ed@448:             # we presuppose endianess of LPC same as PC
ed@448:             lengthstr = ctypes.string_at(ctypes.pointer(ctypes.c_int(length)),4) 
ed@448:             self.pseudofile.write(lengthstr + self.OptData)
ed@448:             
ed@448:             lengthstr = self.pseudofile.read(4)
ed@448:             # transform a byte string into length 
ed@448:             length = ctypes.cast(ctypes.c_char_p(lengthstr), ctypes.POINTER(ctypes.c_int)).contents.value
ed@448:             return self.pseudofile.read(length)
ed@448:         return None
ed@448:         
ed@448: if __name__ == "__main__":
ed@448:     TestConnection = LPCProto()
ed@448: