mdaskalov / dcf77transmitter

DCF77 Transmitter for Tasmota using PWM

General

Simulates the 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). Also draws a digital clock on the dislplay if LVGL is supported.

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:

DCF: 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_offset - integer (default: 60): Time offset of the transmitted time in seconds (by default next minute)

dcf77_dst - boolean (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.