first upload

README

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+Beepy: sync BPC-enabled watches and clocks from Python 3
+--------------------------------------------------------
+This is a Python emulator of the Chinese BPC time broadcasting station signal
+for syncing longwave-enabled watches and clocks that support this station.
+With the help of any sort of loop antenna (or even headphones or speakers), it
+allows you to adjust your watch without having to be close to the Chinese
+signal. This program follows the BPC timecode specification and modulation
+methods used by the oldest desktop applications for this very purpose, and
+transmits on 13700 Hz, whose 5th harmonic is the reference signal frequency,
+68.5 KHz, but the base frequency here is within the spectrum supported by any
+consumer-grade audio hardware.
+
+== Dependencies ==
+
+Beepy depends on PyAudio (>=0.2.14) and ntplib (>=0.4.0). Just install them
+by running pip install -r requirements.txt from the project directory. Note
+that installing PyAudio will also pull its PortAudio (>=v19) dependency.
+
+The program has been primarily tested on Python 3.10.
+
+== Usage ==
+
+Beepy can be run like this:
+
+python bee.py [-t duration] [-d delta] [-s ntp_server] [-n ntp_version] \
+              [-o tz_offset] [-r sample_rate]
+
+All parameters are optional here:
+
+* -h: display help screen
+* -t: transmission duration in minutes (default 30)
+* -d: manual delta correction in milliseconds (default 0, see below)
+* -o: timezone offset from UTC (in hours, default 9, see below)
+* -r: transmission sampling rate (in Hz, default 48000, only change if this
+      fails to work)
+* -s: specify NTP server to fetch time from (if no server is specified, then
+      local system time is used)
+* -n: specify NTP protocol version to use, default is 4, good for most cases
+
+After running the command, you must enter the synchronization mode on your
+watch/clock (making sure that BPC is selected if it's multiband) and put it
+close enough to your (improvised) loop antenna, headphones or speakers. The
+script will fetch the UTC time according to your source, apply the TZ offset,
+then the manual delta offset and then will attempt to start the transmission
+from the closest second. The TZ offset is set to +8 hours by default because
+most BPS-enabled watches/clocks expect the BST time to be sent in order to
+then apply their own timezone correction according to your settings. If your
+watch/clock doesn't have such correction, you can always use this -o flag to
+zero out this offset (with -o 0) and transmit the local time directly onto it.
+In case your equipment, software or time source server introduce any delay to
+the synchronization process, you can add a constant delta (in milliseconds)
+with the -d flag.
+
+After the synchronization is successful, you can press the
+Ctrl+C combination or wait until the entire sequence (which is 30 minutes long
+by default, adjustable with -t flag) gets transmitted.
+
+== FAQ ==
+
+- How is this even possible?
+
+To put it simply, to emit any audio signal, electricity has to travel through
+many wires and coils. This inevitably creates electromagnetic interference. If
+we send the signal of a particular constant frequency with enough intensity
+through audio circuits, this interference will turn into radio emission in the
+longwave spectrum, which is exactly what we need for syncing radio-controlled
+clocks and watches. This emission is too weak to cause any harm outside but
+enough to be received by the watch or clock several centimeters apart.
+
+- Which watches/clocks has this been tested on?
+
+Some Casio models, including Casio GW-B5600BC, GMW-B5000D and GW-5000U.
+
+- Is my particular watch/clock model supported?
+
+As long as it can receive BPC signal and you know how to make it do this, it
+is automatically supported by Beepy. At this point, I can surely say that if 
+anything goes wrong, it's not the fault of your watch or your emulator, but 
+something in between: audio setup, antenna setup or the placement of the watch
+relative to the antenna. It might take some trial and error and a great deal
+of patience to make sure everything works as expected.
+
+For most digital Casio models, you can force BPC reception by entering one
+of the test menus: press and hold first Light, then Receive/Set and then Mode
+button. Scroll through with the Receive button to ensure that "B 01" is on the
+screen, then start the reception process with the Light button. You should get
+a "BOK" message if the process is successful, or "BNG" if unsuccessful.
+
+- Why create an alternative to JJY.py?
+
+In some conditions, multiband Casio watches are proven to sync faster with BPC 
+than with JJY40. Beepy doesn't replace JJY.py as the JJY40 signal is supported
+by much more models. But you can try out Beepy if the JJY reception takes too
+long.
+
+At some time in the future, JJY.py and Beepy might get united into a single
+time synchronization utility.
+
+- Are there still any plans for implementing other longwave time protocols?
+
+Maybe. DCF77 and WWVB are of the primary interest.
+
+== Credits ==
+
+Created by Luxferre in 2024. Released into public domain with no warranties.

bee.py

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+#!/usr/bin/env python3
+# Beepy: a Python standalone script
+# to synchronize time on BPC-enabled wristwatches via headphones
+# Depends on pyaudio and ntplib
+# Created by Luxferre in 2024, released into public domain
+
+import pyaudio, ntplib, math, array, time, datetime
+
+OP_FREQ = 68500/5 # emitted frequency, Hz
+
+# parity calculation helper
+def calc_parity(vals):
+  i = 0
+  for val in vals:
+    i ^= (val & 1) ^ ((val >> 1) & 1)
+  return i
+
+# internal time representation from unix time
+# only fetches the fields necessary for BPC implementation
+def intreptime(unixtm):
+  res = {}
+  tm = time.gmtime(unixtm)
+  res['year'] = tm.tm_year % 100
+  res['month'] = tm.tm_mon
+  res['mday'] = tm.tm_mday
+  res['hour'] = tm.tm_hour - 1
+  if res['hour'] < 0:
+    res['hour'] = 23
+  res['minute'] = tm.tm_min
+  res['second'] = tm.tm_sec
+  # in Python, Monday is 0; in BPC, Sunday is 7 and Monday is 1
+  res['wday'] = tm.tm_wday + 1
+  res['unix'] = int(unixtm) # save the unix time representation
+  return res
+
+# time fetching part (returns China standard time)
+def fetchtime(params = {}):
+  delta = 0.0
+  offset = 28800 # BPC time is UTC+8
+  if 'delta' in params:
+    delta = float(params['delta']) / 1000
+  if 'offset' in params: # base offset from UTC in seconds
+    offset = int(params['offset'])
+  if 'server' in params and params['server'] is not None: # NTP server set
+    ntpver = 3
+    if 'version' in params:
+      ntpver = params['version']
+    c = ntplib.NTPClient()
+    resp = c.request(params['server'], version=ntpver)
+    unixtm = resp.tx_time
+  else: # use current system time by default
+    unixtm = time.time()
+  unixtm += offset + delta # account for delta
+  return intreptime(unixtm)
+
+# timecode generation part
+# accepts the result of fetchtime function
+def gentimecode(ts):
+  # convert ts['hour'] to am/pm (BPC variant)
+  pmflag = 0
+  ampmhr = ts['hour'] % 12
+  if ts['hour'] >= 12:
+    pmflag = 1
+  # init the timecode for the whole minute
+  timecode = [4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+              4,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+              4,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+  # populate hour
+  timecode[3] = timecode[23] = timecode[43] = ampmhr >> 2
+  timecode[4] = timecode[24] = timecode[44] = ampmhr & 3
+  # populate minute
+  timecode[5] = timecode[25] = timecode[45] = (ts['minute'] >> 4) & 3
+  timecode[6] = timecode[26] = timecode[46] = (ts['minute'] >> 2) & 3
+  timecode[7] = timecode[27] = timecode[47] = ts['minute'] & 3
+  # populate weekday
+  timecode[8] = timecode[28] = timecode[48] = (ts['wday'] >> 2) & 1
+  timecode[9] = timecode[29] = timecode[49] = ts['wday'] & 3
+  # populate am/pm flag and first part parity
+  timecode[10] = (pmflag << 1) | calc_parity(timecode[1:10])
+  timecode[30] = (pmflag << 1) | calc_parity(timecode[21:30])
+  timecode[50] = (pmflag << 1) | calc_parity(timecode[41:50])
+  # populate day of month
+  timecode[11] = timecode[31] = timecode[51] = ts['mday'] >> 4
+  timecode[12] = timecode[32] = timecode[52] = (ts['mday'] >> 2) & 3
+  timecode[13] = timecode[33] = timecode[53] = ts['mday'] & 3
+  # populate month
+  timecode[14] = timecode[34] = timecode[54] = ts['month'] >> 2
+  timecode[15] = timecode[35] = timecode[55] = ts['month'] & 3
+  # populate year 
+  yhbit = ts['year'] >> 6
+  timecode[16] = timecode[36] = timecode[56] = (ts['year'] >> 4) & 3
+  timecode[17] = timecode[37] = timecode[57] = (ts['year'] >> 2) & 3
+  timecode[18] = timecode[38] = timecode[58] = ts['year'] & 3
+  # populate the high year bit and the second part parity
+  timecode[19] = (yhbit << 1) | calc_parity(timecode[11:20])
+  timecode[39] = (yhbit << 1) | calc_parity(timecode[31:40])
+  timecode[59] = (yhbit << 1) | calc_parity(timecode[51:60])
+  return timecode
+
+# generate an audio data chunk of specified duration
+def gen_audio(duration, freq=OP_FREQ, sr=48000):
+  smps = int(sr * duration)
+  # create the sine wave array for the whole second
+  rawdata = []
+  for k in range(0, sr):
+    v = math.sin(2 * math.pi * k * freq / sr)
+    if k <= smps: # reduced power mode in the beginning
+      v *= 0.1
+    rawdata.append(int(v * 32767)) # max gain
+  return array.array('h', rawdata).tobytes()
+
+# global buffers for audio data and current position
+curstream = b''
+streampos = 0
+
+# bitcode transmission callback
+def bitcode_transmit(in_data, frame_count, time_info, status):
+  global curstream, streampos
+  framelen = frame_count << 1 # 2 bytes per frame as we're using int16
+  framedata = curstream[streampos:streampos+framelen]
+  streampos += framelen
+  return (framedata, pyaudio.paContinue)
+
+# main logic is here
+def start_transmission(timeparams):
+  global curstream
+  p = pyaudio.PyAudio()
+  sr = timeparams['sr']
+  mins = timeparams['duration']
+  bpc_bit_chunks = [ # pregenerate the chunks
+    gen_audio(0.1, OP_FREQ, sr), # data bits 00
+    gen_audio(0.2, OP_FREQ, sr), # data bits 01
+    gen_audio(0.3, OP_FREQ, sr), # data bits 10
+    gen_audio(0.4, OP_FREQ, sr), # data bits 11
+    gen_audio(0, OP_FREQ, sr)    # transmission start chunk 
+  ]
+  ts = fetchtime(timeparams) # get the current timestamp
+  print('Time fetched (Unix):', ts['unix'])
+  bitcode = gentimecode(ts)[ts['second']+1:] # slice the rest of current minute
+  nextmin = ts['unix'] - ts['second'] # rewind to start of the minute
+  for i in range(0, mins): # generate bitcode for the next N minutes
+    nextmin += 60 # calc the next minute
+    bitcode += gentimecode(intreptime(nextmin))
+  print("Transmitting... Press Ctrl+C to exit")
+  # wait for the next second to start (roughly, with all the call overhead)
+  time.sleep((1 - datetime.datetime.now().microsecond/1000000)/2)
+  # open a PyAudio stream with callback
+  stream = p.open(format=pyaudio.paInt16, channels=1, frames_per_buffer=16384,
+            rate=sr, output=True, stream_callback=bitcode_transmit)
+  curstream = bpc_bit_chunks[bitcode.pop(0)] # preload the first second
+  while stream.is_active(): # wait for the stream to finish
+    if len(bitcode) > 0: # feed the stream in parallel
+      curstream += bpc_bit_chunks[bitcode.pop(0)]
+    time.sleep(0.75) # feeding the stream should be faster than realtime
+  # close audio
+  stream.stop_stream()
+  stream.close()
+  p.terminate()
+  print("Transmission ended")
+
+if __name__ == '__main__':
+  from argparse import ArgumentParser
+  parser = ArgumentParser(description='Beepy: an opensource longwave time synchronizer for BPC-enabled watches and clocks', epilog='(c) Luxferre 2024 --- No rights reserved <https://unlicense.org>')
+  parser.add_argument('-t', '--duration', type=int, default=30, help='Transmission duration (in minutes, default 30)')
+  parser.add_argument('-d', '--delta', type=int, default=0, help='Manual delta correction (in ms, must be determined individually, 0 by default)')
+  parser.add_argument('-o', '--tz-offset', type=float, default=9, help='Timezone offset from UTC to transmit (in hours, default 9 - corresponds to JST)')
+  parser.add_argument('-r', '--sample-rate', type=int, default=48000, help='Transmission sampling rate (in Hz, default 48000)')
+  parser.add_argument('-s', '--ntp-server', type=str, default=None, help='NTP server to sync from (if not specified then will sync from the local system time)')
+  parser.add_argument('-n', '--ntp-version', type=int, default=4, help='NTP protocol version to use (default 4)')
+  args = parser.parse_args()
+  params = { # populate parameters from the command line
+    'server': args.ntp_server, 'version': args.ntp_version,
+    'delta': args.delta, 'offset': int(args.tz_offset * 3600),
+    'sr': args.sample_rate, 'duration': args.duration
+  }
+  start_transmission(params)

requirements.txt

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+pyaudio>=0.2.14
+ntplib>=0.4.0