#!/usr/bin/python -u
 # The -u option turns off block buffering of python output. This assures
 # that output streams to stdout when output happens.
 #
 # Description:  This program passes commands from a command line prompt
 #               directly through to the FT991.  Also a few utility macro
 #               commands have been defined that can be typed on the 
 #               command line.
 #
 # This script has been tested with the following
 #
 #     Python 2.7.15rc1 (default, Nov 12 2018, 14:31:15) 
 #     [GCC 7.3.0] on linux2
 #2345678901234567890123456789012345678901234567890123456789012345678901234567890
 
 import sys, serial, time
 
 # Determine OS type and set device port accordingly.
 OS_type = sys.platform
 if 'WIN' in OS_type.upper():
     _SERIAL_PORT = 'COM5'
 else:
     _SERIAL_PORT = '/dev/ttyUSB0'
 
 # General constant defines
 _BAUD_RATE = 9600
 _INTERFACE_TIMEOUT = 0.1 # seconds
 _SERIAL_READ_TIMEOUT = 0.1 # seconds
 _SERIAL_READ_BUFFER_LENGTH = 1024 # characters
 
 # Define functions encapsulating serial communications to and from
 # a generic serial device object.
 
 def getAnswer(device, termchar):
     """
     Description: Reads output one character at a time from the device
                  until a terminating character is received.  Returns a     
                  string containing the characters read from the serial
                  port.
     Parameters:  device - a serial object connected to the device port
                  termchar - character terminating the answer string
     Returns:     string
     """
     answer = '' # initialize answer string to empty string
     charCount = 0  # reset read character count to zero
 
     while True:
         startTime = time.time() # Start read character timer
         c =''
         while True:
             # Check for a character available in the serial read buffer.
             if device.in_waiting:
                 c = device.read()
                 break
             # Timeout if a character does not become available.
             if time.time() - startTime > _SERIAL_READ_TIMEOUT:
                 break # Read character timer has timed out.
         # Return empty string if a character has not become available.
         if c == '':
             break;
         answer += c # Form a string from the read characters.
         charCount += 1 # Increment character count.
         # If a semicolon has arrived then the FT991 has completed
         # sending output to the serial port so stop reading characters.
         # Also stop if max characters received. 
         if c == termchar:
             break
         if charCount > _SERIAL_READ_BUFFER_LENGTH:
             raise Exception('serial read buffer overflow')
     device.flushInput() # Flush serial buffer to prevent overflows.
     return answer           
 ## end def
 
 def sendCommand(device, command):
     """
     Description: writes a string to the device.
     Parameters:  device - a serial object connected to the device port
                  command - string containing the FT991 command
     Returns:     nothing
     """
     device.write(command) # Send command string to FT991
     device.flushOutput() # Flush serial buffer to prevent overflows
 
 # Iterate through all menu items, getting each setting
 def readMenuSettings(device):
     """
     Description: prints out all menu settings.
     Parameters:  device - a serial object connected to the FT991
     Returns:     nothing
     """
     for inx in range(1,125):
         sCommand = 'EX%0.3d;' % inx
         sendCommand(device, sCommand)
         sAnswer = getAnswer(device, ';')
         print "%0.3d: %s" % (inx, sAnswer[5:])
 
 # Iterate through all memory channels, getting settings
 def readMemoryChannels(device):
     """
     Description: prints out all memory channels.
     Parameters:  device - a serial object connected to the FT991
     Returns:     nothing
     """
     for inx in range(1,118):
         sCommand = 'MT%0.3d;' % inx
         sendCommand(device, sCommand)
         sAnswer = getAnswer(device, ';')
         print "%0.3d: %s" % (inx, sAnswer)
 
 def main():
     """
     Description: main routine starts command line interpreter.
     Parameters:  none
     Returns:     nothing
     """
     
     # Present an introductory splash when the program first starts up.
     splash = \
 """
 Enter an FT991 command, e.g, "IF;";
 or enter one of the following commands
     exit - terminates this program
     rmem - prints out memory channels
     rmenu - prints out all menu settings
 """
     print splash
 
     # Create a FT991 object for serial communication
     ft991 = serial.Serial(_SERIAL_PORT, _BAUD_RATE, timeout=_INTERFACE_TIMEOUT)
     time.sleep(.1) # give the connection a moment to settle
 
     while(True):
         sCommand = raw_input('>')
         # Process command string
         if sCommand == '': # no command - do nothing
             continue
         elif sCommand.upper() == 'EXIT': # end program
             break
         elif sCommand.upper() == 'RMEM': # display channel memory
             readMemoryChannels(ft991)
         elif sCommand.upper() == 'RMENU': # display menu settings
             readMenuSettings(ft991)
         else: # run a user command
             sendCommand(ft991, sCommand)
             sAnswer = getAnswer(ft991, ';');
             if sAnswer != '':
                 print sAnswer
 ## end main
 
 if __name__ == '__main__':
     main()