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