File content as of revision 3:1b3329242491:

#!/usr/bin/python -tt                           # tt: detect mixed space/tab.
#---copyright-----------------------------------#-------------------------------
#   licensed for personal and academic use.
#   commercial use must be approved by the account-holder of
#   gated.clock@gmail.com
#-------imports---------------------------------#-------------------------------
import serial                                   # serial over USB.
#=======class===================================#===============================
if (1):
        class mmUSBserial():                    # USB class.
#-----------------------------------------------#-------------------------------
                                                # constructor.
          def __init__(self, idVendor, idProduct):      

            self.__idVendor  = idVendor         # promote to object scope.
            self.__idProduct = idProduct        # promote to object scope.

            openSuccess = 1
            self.__serialPort = serial.Serial()
            self.__serialPort.baudrate = 115200 # was 9600
            self.__serialPort.timeout  =    1   # one-second timeout.

            for portIndex in range(7, -1, -1):
              portString = "/dev/ttyACM" + "{}".format(portIndex)
              self.__serialPort.port = portString
              try:
                self.__serialPort.open()
              except:
                print("failed to open port {}.").format(portString)
                openSuccess = 0

              if (openSuccess): break
              openSuccess = 1

            if (openSuccess): print("successfully opened port {}.").format(portString)
            else:             print("could not open any port.")

            self.__SER_BYTES = 18               # same as mbed program's SER_BYTES.
#-----------------------------------------------#-------------------------------  
          def __del__(self):                    # destructor.
            self.__serialPort.close()
            print "object destroyed."
#-----------------------------------------------#-------------------------------
#         the number of bytes written and read must both be SER_BYTES.
#         the '$' must be in bit<7> of what's written.

          def write(self,toWrite):              # write a string.
            nowWrite = toWrite[:7]
            nowWrite = nowWrite + "$"           # in <7>.
            if (self.__SER_BYTES > 8):          # flush out with 0's.
              for loopIndex in range (0, self.__SER_BYTES - 8):
                nowWrite = nowWrite + "0"
#           print("nowWrite {}").format(nowWrite)
            self.__serialPort.write(nowWrite)
            return(nowWrite)
#-----------------------------------------------#-------------------------------
          def read(self):                       # read a string.
            gotRead = self.__serialPort.read(self.__SER_BYTES)
#           print("gotRead {}").format(gotRead)
            return(gotRead)
#-----------------------------------------------#-------------------------------
#===============================================#===============================