DCF-77 Decoder for Long Wave Time Signal Receiver for P1 Tachyon Forth
Christof Eb.
Posts: 1,195
Hi,
perhaps this is of interest for others.
This is a nice and cheap way to automatically set the built-in software clock of Tachyon Forth.
DCF-77 is a long wave time signal sender in Frankfurt, Germany that can be used in a range of about 2000km, they say. It sends the precise time and date.
https://en.wikipedia.org/wiki/DCF77
I use a module from Pollin. https://www.pollin.de/productdownloads/D810054B.PDF
This has positive pulses. Some other modules provide negative pulses.
The code starts the receiver und decodes the signal (minutes and hours). After 2 consecutive minutes, the new result will be compared with the previous one ( + 1 Minute ) to see, if the reception was good. If yes, the software clock will be updated.
The code tries to deal with false pulses due to disturbance of reception. There are lots of additional short positive pulses and less often an intended positive pulse is disrupted with a false negative one. At this moment it will update the builtin software clock of Tachyon within a few minutes at my place in southern Germany.
In the code there is an output for a clock face consisting of a neopixel WS2812 ring of 12 positions with 3 colors each. It will show the last full hour in Red, the last 5 Minutes in Green and the last 5 Seconds in Blue.
As the code can use a lot of builtin functions of Tachyon, it does only occupy about 700 bytes of RAM.
Many thanks for Tachyon, Peter. It is a joy to work with! (I love your implementation of CASE and CASES!)
And also many thanks to the people, who put work into the documentation of Tachyon and Taquoz!
Have fun, Christof
Updated, it did stall at midnight
Comments
see my PM
That is a very useful module, Christof. I did one on a zx spectrum years ago. A very low cost source of precision time.
Yes, that is true. The downside, and sometimes that may be even a show stopper, is the size of the LW ferrite antenna. However, the RF controlled clocks are not so big, after all
The obvious alternative is GPS module or, if the super long term accuracy is not that critical, a precise RTC such as the RV-3028 for example, which happens to be an ultra low power one as well.
Antennas - The GPS antenna needs to see the sky, so window or external mount required. The DCF-77 antenna just needs orienting for best signal local to the equipment (providing the building isn't shielded)
Our kitchen clock is locked to DCF-77 and all we did was hang it on the wall.