Control a DG-4 filter wheel over a serial port

dg4.py

from serial import Serial
from time import sleep

class DG4(object):
    """Control a Sutter Lambda DG-4 over serial interface"""
    SWITCH_TO_SERIAL = 238 # switch the DG4 to serial mode, DG4 hangs until it receives the next serial command
    FREEZE_DISPLAY = 218
    TURN_DISPLAY_ON = 219
    OPEN_SHUTTER = 170
    ND_ADJ_MARKER = 171 # DATANUM = 171 MARKER BETWEEN 235 OR 236 IN N.D. ADJUST
    CLOSE_SHUTTER = 172
    ENABLE_TURBO_BLANKING =186
    DISABLE_TURBO_BLANKING = 188
    TRIGGERED_BY_STROBE = 202
    DISABLE_TRIGGERED_BY_STROBE = 203
    SELECT_VIDEO_SYNC = 204
    DISABLE_VIDEO_SYNC = 205
    SELECT_VIDEO_SYNC_GATED_BY_STROBE_LOW = 206
    DISABLE_VIDEO_SYNC_GATED_BY_STROBE_LOW = 207
    START_LOADING_RING_BUFFER = 223 #START LOADING RING BUFFER (UP TO 256 VALUES)
    START_REMOTE_CHANGE_OF_ND_FILTER_SETTING = 234 #START REMOTE CHANGE OF N.D. FILTER SETTING
    INCREASE_THE_DAC_GALVO_VALUE = 235 #-SEND 171 AS SPACE
    DECREASE_THE_DAC_GALVO_VALUE  = 236 # -SEND 171 AS SPACE
    END_CHANGE_OF_ND_FILTER_SETTING_AND_SAVE = 237
    FORCE_ONLINE_FOR_CHANNEL_THAT_RECEIVED_IT = 238
    END_LOADING_RING_BUFFER_FILTERS = 240
    RUN_RING_BUFFER = 241 # (FIRST SELECT TRIGGER SOURCE)
    END_RING_BUFFER_RUN = 242

    def __init__(self, com=0, latency=0.1):
        self.latency = latency
        self.ser = Serial(com)
        self.sendrecv(DG4.SWITCH_TO_SERIAL)

    def __enter__(self):
        self.sendrecv(DG4.SWITCH_TO_SERIAL)
        return self

    def __exit__(self, type, value, traceback):
        self.ser.close()

    def setup_ring_buffer(self, sequence):
        """Sets up the DG-4's ring buffer with the given integer sequence"""
        self.sendrecv(DG4.START_LOADING_RING_BUFFER)
        for i in sequence:
            self.sendrecv(i)
        self.sendrecv(DG4.END_LOADING_RING_BUFFER_FILTERS)

    def send(self, msg):
        """Send an integer command, handles the conversion to bytes"""
        self.ser.write(chr(msg))

    def sendrecv(self, msg):
        """Send an integer command and print any reply"""
        self.send(msg)
        sleep(self.latency)
        while self.ser.inWaiting():
            reply = ord(self.ser.read(1))
            print "dg-4: %d" % reply
        return True

# A table of custom command aliases for our application
command_table = {
    'strobe':       DG4.TRIGGERED_BY_STROBE,
    'white':        1,
    'red':          2,
    'yfp':          1,
    'nearbeads':    2,
    'farbeads':     1,
    '380':          3,
    '340':          4,
    'fura':         DG4.RUN_RING_BUFFER,
    '':             DG4.END_RING_BUFFER_RUN
}
        

if __name__ == '__main__':
    with DG4() as dg:
        dg.sendrecv(DG4.TRIGGERED_BY_STROBE)
        dg.setup_ring_buffer([3, 4])
        cmd = 'start'
        while True:
            cmd = raw_input("Enter command...")
            try:             
                dg.sendrecv(command_table[cmd])
            except KeyError as e:
                if cmd != 'quit' and cmd != 'q':
                    print "'%s' not a valid command to DG4" % cmd
                    print "Valid commands are: " + ", ".join([k  if k != '' else '<Enter>' for k in sorted(command_table)])
                else:
                    break