Create README.md

README.md

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+## General 
+
+Simulates the [DCF77](https://en.wikipedia.org/wiki/DCF77) time code signal on a GPIO pin. It uses PWM with carrier frequency set to 25.833 kHz (third harmonic) as Tasmota limits the max PWM frequency to 50kHz (look for `PWM_MAX` in the source code).
+
+## Installation
+Upload the Tasmota appication `DCF77Transmitter.tapp` to the file system and reboot. The application run in the background and the transmitted data is written in the logs:
+
+```
+DCF77: Sun 04.02.24 16:02 CET: 0-00000000000000-000101-00100001-0110101-001000-111-01000-001001001
+```
+
+To build manually, execute following in the repo directory
+```
+rm -f DCF77Transmitter.tapp; zip -j -0 DCF77Transmitter.tapp src/*.be
+```
+## Configuration
+The signal is submitted to the first configured PWM pin, check with: `gpio.pin(gpio.PWM1)` 
+
+Following parameter could be configured in the `persist` module:
+
+`dcf77_time_offset` - boolean (default: 0): Specify the time offset of the transmitted time (by default next minute)
+
+`dcf77_dst` - integer (default: false): By default the local time is submitted as CET. Set to `true` to submit it as CEST.
+
+## Antenna
+Best results are achieved if you connect a ferrite antenna over 330 ohm resistor and a capactior to ground.
+
+It also works with analog beeper or even with a led connected to the GPIO pin. 
+
+Normally the clock gets syncrhonized in about two minutes depending on the distance and signal strength.