使用RaspberryPi的DCF77、WWVB、JJY和MSF时钟LF波段信号发射器_C++_CMake_下载.zip

Radio time station transmitter using the Raspberry Pi and Nvidia Jetson ===================================================== I am living in a country where there is no [DCF77] sender nearby for my European radio controlled wristwatch to get its time. This vintage Junghans Mega doesn't have any buttons to set the time, so to bring it back to life, I built my own 'transmitter', taking the [NTP] time of a Raspberry Pi and generating a modulated signal via GPIO pins to then magnetically couple it into the watch ferrite. Since many other long-wave time stations around the world use similar concepts of sending amplitude modulated time, other time services have been added. This program is useful if you have a clock that otherwise does not get any reception. This magnetical coupling is very low power and only works over a few centimeters, but **_before running this program, make sure you follow your local laws with regard to restrictions on radio transmissions._** ### Platform txtempus supports Raspberry Pi series and Nvidia Jetson Series (experimental). #### Raspberry Pi So far, it has been tested on a Pi3 and a Pi Zero W. There has been a report of different frequencies generated with an older Pi (Bug #1), so until we have a definitive list of available clock sources inside these, check out that bug for a workaround. #### Nvidia Jetson Series (experimental) So far, it has been tested only on a Jetson Nano, but all Jetson devices except for TX1 and TX2 (there is no available pwm pin) are supported. ### Supported Time Services #### DCF77 The [DCF77] (Germany) signal is a 77.5kHz carrier, that is amplitude modulated with attenuations every second of the minute except the 59th to synchronize. The length of the attenuation (100ms and 200ms) denotes bit values 0 and 1 respectively so in each minute, 59 bits can be transferred, containing date and time information. The Raspberry Pi has ways to create frequencies by integer division and fractional jitter around that, which allows us to generate a frequency of 77500.003Hz, which is close enough. Can be chosen with `-s DCF77` option. #### WWVB The [WWVB] (USA) is on a 60kHz carrier, and also transmits one bit per second with different attenuation times (200ms zero, 500ms one; 800ms sync) and multiple synchronization bits. Use `-s WWVB` option for this one. #### MSF The [MSF] (United Kingdom) has yet another encoding, transferring two bits per second. Carrier is 60kHz. Option is `-s MSF`. #### JJY The [JJY] (Japan) is similar to WWVB, with same timings of carrier switches, but reversed power levels. Some bits are different. Two senders exist in Japan with 40kHz and 60kHz carrier; their simulations can be chosen with command line options `-s JJY40` and `-s JJY60`. If you're in/or want to display a different time-zone, issue [#17](https://github.com/hzeller/txtempus/issues/17) might be of interest to you. ### Minimal External Hardware #### Raspberry Pi The external hardware is simple: we use the frequency output on one pin and another pin to pull the signal to a lower level for the regular attenuation. To operate, you need three resistors: 2x4.7kΩ and one 560Ω (precision not critical), wired to GPIO4 and GPIO17 like so: Schematic | Real world -------------------------------|------------------------------  | GPIO4 and 17 are on the inner row of the Header pin, three pins inwards on the [Raspberry Pi GPIO]-Header. You don't need GPIO17 and the 560Ω resistor for `MSF`, as that works with switching the signal (on-off keying) instead of attenuating. In that case, you can replace the sequence of two 4.7kΩ resistors with a single 10kΩ. Now, wire a loop of wire between the open end of the one 4.7kΩ and ground - this loop acts as coupling coil to the watch ferrite antenna. The signal is very weak, so bring this wire-loop close to your radio watch/clock. In the following image, which was the first experiment, it is wrapped around the antenna, but it is not strictly needed: anything within a few centimeters should work.  Being too close to the clock can confuse a sensitive receiver, so you might need to experiment with the distance. If your clock/watch is not receiving, add more turns to your transmission coil. In the picture at the bottom of the page you see that I am using about 10-20 turns on the coil (reddish oval lying on the Pi). This set-up should work for most watches if you have them in close vicinity. The antenna set-up is intentionally not optimal to just be good enough for a local watch but hopefully not causing interference. Further improvements of course can be done to the antenna for increased transmission distance, such as using a ferrite, making it an LC circuit or adding an amplifier. *Only go in this direction after familiarizing yourself with allowances of radio transmissions in your area on your frequency of interest.* #### Nvidia Jetson Series (experimental) (*Please read the external hardware for the Raspberry Pi above first.) On Jetson, the external hardware setup is slightly different from the Raspberry Pi. We need one "PWM Pin" for a frequency output, and one "Attenuation Pin" for modulating the signal. These pins vary by the Jetson model. Please check the following table. |Devices|PWM pin (Board numbering)|Attenuation pin (Board numbering)| |-------|-------------------------|---------------------------------| |Jetson TX1, Jetson TX2|Not supported|Not supported| |Jetson Xavier, Clara AGX Xavier, Jetson Orin|18|16| |Other devices|33|35| To operate, you need three resistors: 2x4.7kΩ and one 560Ω (precision not critical) and one NPN transistor (nearly any NPN transistor should work. I'm using KTC3198). Here's the full schematic of the external hardware for the Jetson Series: Schematic | Real world (Jetson Nano) -------------------------------|------------------------------  | Like the Raspberry Pi, you don't need the Attenuation Pin and the 560Ω resistor for `MSF`, and a wire-loop between the 4.7kΩ register and the ground acts as coupling coil. Bring this wire-loop close to your radio watch/clock.  ### Build ``` sudo apt-get install git build-essential cmake -y git clone https://github.com/hzeller/txtempus.git cd txtempus mkdir build && cd build ``` #### Rapberry Pi ``` cmake ../ # or cmake ../ -DPLATFORM=rpi make ``` #### Nvidia Jetson Series (experimental) Before you build txtempus on your Jetson: - You should install [JetsonGPIO](https://github.com/pjueon/JetsonGPIO) which is a library that enables the use of Jetson's GPIOs. - The system pinmux must be configured to connect the hardware PWM controlller(s) to the relevant pins. Read the L4T documentation for details on how to configure the pinmux. ``` cmake ../ -DPLATFORM=jetson make ``` ### Transmit! ``` sudo ./txtempus -v -s DCF77 ``` With `-s`, you set the type of time signal you want to transmit. There are a few options you can set. The `-r` option is useful to have the program run only for the few minutes it might take for a clock to synchronize. By default, the current system time is transmitted. The `-t` option allows different times for testing. ``` usage: ./txtempus [options] Options: -s <service> : Service; one of 'DCF77', 'WWVB', 'JJY40', 'JJY60', 'MSF' -r <minutes> : Run for limited number of minutes. (default: no limit) -t 'YYYY-MM-DD HH:MM' : Transmit the given local time (default: now) -z <minutes> : Transmit the time offset from local (default: 0 minutes) -v : Verbose. -n : Dryrun, only showing modulation envelope. -h : This help. ``` #### Don't connect monitor (Raspberry Pi) Don't connect a monitor to the Pi, just operate it headless. Th