src/savemysugar/CallDistanceTransceiver.py

   1 #!/usr/bin/env python3
   2 #
   3 # CallDistanceTransceiver - send and receive Morse using phone calls distance
   4 #
   5 # Copyright (C) 2015  Antonio Ospite <ao2@ao2.it>
   6 #
   7 # This program is free software: you can redistribute it and/or modify
   8 # it under the terms of the GNU General Public License as published by
   9 # the Free Software Foundation, either version 3 of the License, or
  10 # (at your option) any later version.
  11 #
  12 # This program is distributed in the hope that it will be useful,
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 # GNU General Public License for more details.
  16 #
  17 # You should have received a copy of the GNU General Public License
  18 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19
  20
  21 # This hack allows importing local modules also when
  22 # __name__ == "__main__"
  23 try:
  24     from .MorseDistanceModulator import MorseDistanceModulator
  25     from .MorseTranslator import MorseTranslator
  26 except SystemError:
  27     from MorseDistanceModulator import MorseDistanceModulator
  28     from MorseTranslator import MorseTranslator
  29
  30 import logging
  31 import time
  32
  33
  34 def log_symbol(distance, symbol, extra_info=""):
  35     logging.info("distance: %.2f Received \"%s\"%s", distance, symbol,
  36                  extra_info)
  37
  38
  39 class CallDistanceTransceiver(object):
  40     """Transmit Morse messages using the distance between calls.
  41
  42     This is basically a pulse-distance modulation (PDM).
  43
  44     A RING is a pulse and the Morse symbols are encoded in the pause between
  45     the first ring of the previous call and the first ring of a new call.
  46
  47     This strategy is very slow but it can even be used with ancient analog
  48     modems which don't have call progress notifications for outgoing calls, and
  49     make it also hard to count multiple rings in the same call on the receiving
  50     side because there is no explicit notification on the receiving side of
  51     when the caller ends a calls.
  52
  53     For GSM modems, which have a more sophisticate call report signalling,
  54     a more efficient encoding can be used (for example using ring counts to
  55     encode Morse symbols, i.e. a pulse-length modulation), but for
  56     a proof-of-concept, a slow encoding covering the most general setup is
  57     fine.
  58
  59     Plus, supporting communications between analog modems is cool :)
  60     """
  61
  62     def __init__(self, modem,
  63                  call_setup_time_min=7, call_setup_time_max=15,
  64                  ring_time_min=4.8, ring_time_max=5.2,
  65                  add_inter_call_distance=True):
  66         """Encode the Morse symbols using the distance between calls.
  67
  68         Args:
  69
  70             call_setup_time_min: the minimum time between  when the transmitter
  71                 dials the number and the receiver reports RING notifications.
  72             call_setup_time_max: the maximum time between when the transmitter
  73                 dials the number and the receiver reports RING notifications.
  74                 Waiting this time after dialing ensures that the receiver has
  75                 received _at_least_ one ring. The default chosen here have been
  76                 tested to work fine with old analog modems, provided that there
  77                 is some more distance between two calls, and with Android
  78                 receivers.
  79             ring_time_min: the minimum time between two consecutive RINGs
  80                 in the same call.
  81             ring_time_max: the maximum time between two consecutive RINGs
  82                 in the same call, the standard interval is about 5 seconds, but
  83                 line and/or software delays can make it vary.  This is needed
  84                 in order to ignore multiple ring in the same call when multiple
  85                 RING in the same call are notified, and then be able to
  86                 discriminate between two different calls.
  87             add_inter_call_distance: specify if it is needed to wait an extra
  88                 fixed time between calls.
  89             """
  90
  91         self.modem = modem
  92         self.translator = MorseTranslator()
  93
  94         self.call_setup_time_max = call_setup_time_max
  95
  96         if add_inter_call_distance:
  97             # Analog modems don't like to dial a new call immediately after
  98             # they hung up the previous one; an extra delay of about one
  99             # ring time makes them happy.
 100             inter_symbol_distance = ring_time_max
 101         else:
 102             inter_symbol_distance = 0
 103
 104         self.modulator = MorseDistanceModulator(call_setup_time_min,
 105                                                 call_setup_time_max,
 106                                                 ring_time_min,
 107                                                 ring_time_max,
 108                                                 inter_symbol_distance)
 109
 110         logging.debug("call setup time between %.2f and %.2f "
 111                       "--------- dot transmit time: %.2f + %.2f "
 112                       "receive time: between %.2f and %.2f",
 113                       self.modulator.period_min,
 114                       self.modulator.period_max,
 115                       self.modulator.period_max,
 116                       self.modulator.dot_time.dist,
 117                       self.modulator.dot_time.min,
 118                       self.modulator.dot_time.max)
 119         logging.debug("call setup time between %.2f and %.2f "
 120                       "-------- dash transmit time: %.2f + %.2f "
 121                       "receive time: between %.2f and %.2f",
 122                       self.modulator.period_min,
 123                       self.modulator.period_max,
 124                       self.modulator.period_max,
 125                       self.modulator.dash_time.dist,
 126                       self.modulator.dash_time.min,
 127                       self.modulator.dash_time.max)
 128         logging.debug("call setup time between %.2f and %.2f "
 129                       "- signalspace transmit time: %.2f + %.2f "
 130                       "receive time: between %.2f and %.2f",
 131                       self.modulator.period_min,
 132                       self.modulator.period_max,
 133                       self.modulator.period_max,
 134                       self.modulator.signalspace_time.dist,
 135                       self.modulator.signalspace_time.min,
 136                       self.modulator.signalspace_time.max)
 137         logging.debug("call setup time between %.2f and %.2f "
 138                       "--- wordspace transmit time: %.2f + %.2f "
 139                       "receive time: between %.2f and %.2f",
 140                       self.modulator.period_min,
 141                       self.modulator.period_max,
 142                       self.modulator.period_max,
 143                       self.modulator.wordspace_time.dist,
 144                       self.modulator.wordspace_time.min,
 145                       self.modulator.wordspace_time.max)
 146         logging.debug("call setup time between %.2f and %.2f "
 147                       "--------- EOM transmit time: %.2f + %.2f "
 148                       "receive time: between %.2f and inf",
 149                       self.modulator.period_min,
 150                       self.modulator.period_max,
 151                       self.modulator.period_max,
 152                       self.modulator.eom_time.dist,
 153                       self.modulator.eom_time.min)
 154
 155         self.previous_ring_time = -1
 156         self.previous_call_time = -1
 157
 158         self.morse_message = ""
 159         self.text_message = ""
 160
 161         self.end_of_message = False
 162
 163     def receive_symbol(self):
 164         current_ring_time = time.time()
 165
 166         if self.previous_ring_time == -1:
 167             self.previous_ring_time = current_ring_time
 168             self.previous_call_time = current_ring_time
 169             log_symbol(0, "", "(The very first ring)")
 170             return
 171
 172         ring_distance = current_ring_time - self.previous_ring_time
 173         logging.debug("RINGs distance: %.2f", ring_distance)
 174         self.previous_ring_time = current_ring_time
 175
 176         # Ignore multiple rings in the same call
 177         if self.modulator.is_same_period(ring_distance):
 178             logging.debug("multiple rings in the same call, distance: %.2f",
 179                           ring_distance)
 180             return
 181
 182         call_distance = current_ring_time - self.previous_call_time
 183         self.previous_call_time = current_ring_time
 184
 185         try:
 186             symbol = self.modulator.distance_to_symbol(call_distance)
 187         except ValueError as err:
 188             logging.error("%s", err)
 189             logging.error("Check the transmitter and receiver parameters")
 190             return
 191
 192         extra_info = ""
 193         if symbol in [" ", "/", "EOM"]:
 194             signal = self.morse_message.strip().split(' ')[-1]
 195             character = self.translator.signal_to_character(signal)
 196             extra_info = " got \"%s\"" % character
 197
 198         log_symbol(call_distance, symbol, extra_info)
 199
 200         if symbol != "EOM":
 201             # Add spaces around the wordspace symbol to make it easier to split
 202             # the Morse message in symbols later on
 203             if symbol == "/":
 204                 symbol = " / "
 205             self.morse_message += symbol
 206         else:
 207             self.end_of_message = True
 208             self.previous_ring_time = -1
 209             self.previous_call_time = -1
 210
 211     def receive_loop(self):
 212         while not self.end_of_message:
 213             self.modem.get_response("RING")
 214             self.receive_symbol()
 215             logging.debug("Current message: %s", self.morse_message)
 216
 217         self.end_of_message = False
 218         self.text_message = self.translator.morse_to_text(self.morse_message)
 219         self.morse_message = ""
 220
 221     def get_text(self):
 222         return self.text_message
 223
 224     def transmit_symbol(self, destination_number, symbol, sleep_time):
 225         logging.info("Dial and wait %.2f = %.2f + %.2f seconds "
 226                      "(transmitting '%s')",
 227                      self.call_setup_time_max + sleep_time,
 228                      self.call_setup_time_max,
 229                      sleep_time,
 230                      symbol)
 231
 232         # Dial, then wait self.call_setup_time_max to make sure the receiver
 233         # gets at least one RING, and then hangup and sleep the time needed to
 234         # transmit a symbol.
 235         self.modem.send_command("ATDT" + destination_number + ";")
 236         time.sleep(self.call_setup_time_max)
 237         self.modem.send_command("ATH")
 238         self.modem.get_response()
 239         time.sleep(sleep_time)
 240
 241     def transmit(self, message, destination_number):
 242         morse_message = self.translator.text_to_morse(message)
 243         distances = self.modulator.modulate(morse_message)
 244
 245         logging.debug("Starting the transmission")
 246         for i, distance in enumerate(distances):
 247             # Use 'None' for the last call
 248             if i == len(distances) - 1:
 249                 symbol = None
 250             else:
 251                 total_sleep_time = self.call_setup_time_max + distance
 252                 symbol = self.modulator.distance_to_symbol(total_sleep_time)
 253
 254             self.transmit_symbol(destination_number, symbol, distance)
 255
 256     def estimate_transmit_duration(self, message):
 257         morsemessage = self.translator.text_to_morse(message)
 258         logging.debug(morsemessage)
 259
 260         distances = self.modulator.modulate(morsemessage)
 261
 262         transmitting_time = 0
 263         for distance in distances:
 264             transmitting_time += self.call_setup_time_max
 265             transmitting_time += distance
 266
 267         logging.debug("Estimated transmitting time: %.2f seconds",
 268                       transmitting_time)
 269
 270
 271 def test_transmit_receive():
 272     logging.basicConfig(level=logging.DEBUG)
 273     call_setup_time_min = 0
 274     call_setup_time_max = 0.01
 275     ring_time_min = 0
 276     ring_time_max = 0
 277
 278     import random
 279
 280     class DummyModem(object):
 281         """Always receive a '.', a '/' and then EOM, which results in 'E '."""
 282
 283         def __init__(self):
 284             self.ring_count = 0
 285
 286             # Take trasmission times from a transceiver
 287             self.transceiver = None
 288
 289             random.seed(None)
 290
 291         def send_command(self, command):
 292             pass
 293
 294         def get_response(self, response=None):
 295             # pylint: disable=unused-argument
 296
 297             setup_time = random.uniform(self.transceiver.modulator.period_min,
 298                                         self.transceiver.modulator.period_max)
 299
 300             if self.ring_count == 0:
 301                 # dummy ring
 302                 pass
 303             elif self.ring_count == 1:
 304                 # received a '.'
 305                 dot_time = self.transceiver.modulator.dot_time.dist
 306                 time.sleep(setup_time + dot_time)
 307             elif self.ring_count == 2:
 308                 # received a '/'
 309                 wordspace_time = self.transceiver.modulator.wordspace_time.dist
 310                 time.sleep(setup_time + wordspace_time)
 311             else:
 312                 # received an 'EOM'
 313                 eom_time = self.transceiver.modulator.eom_time.dist
 314                 time.sleep(setup_time + eom_time)
 315
 316             self.ring_count += 1
 317             self.ring_count %= 4
 318
 319     modem = DummyModem()
 320
 321     xcv = CallDistanceTransceiver(modem,
 322                                   call_setup_time_min, call_setup_time_max,
 323                                   ring_time_min, ring_time_max, True)
 324
 325     modem.transceiver = xcv
 326
 327     xcv.transmit("CODEX PARIS", "0")
 328
 329     while True:
 330         modem.ring_count = 0
 331         xcv.receive_loop()
 332         print()
 333         print("Message received!")
 334         print("\"%s\"" % xcv.get_text(), flush=True)
 335
 336
 337 if __name__ == "__main__":
 338     test_transmit_receive()