Very wrong frequency generated (1.6kHz instead of 60kHz)

[TheGuv]

Hello H,

Many thanks for this project. I was looking for exactly this for my Casio watch since I moved countries.
It built fine and appears to run but generates very low frequencies on my RPi model B+ v1.2. I'm not 100% sure what Pi you are using so it could well be you have a different model.

Using './txtempus -s MSF' insead of 60kHz, my 'scope shows only 1.611kHz and of course no devices work. Same with WWVB option. Trying the DCF77 produces 2.081kHz instead of 77.5kHz.

Would you have any ideas?

'guv.

[hzeller]

Interesting, maybe Rasbperry Pi changed the frequency of various internal oscillators between versions ?

You find the base assumptions of the various osciallator frequencies here:
https://github.com/hzeller/txtempus/blob/master/gpio.cc#L117

This chooses from various oscillators that would be best, I think it uses the 216Mhz HDMI frequency for 77.5kHz. If it is only a few kHz, this sounds like the oscillator is on a frequency in the few Mhz range. Is HDMI enabled on the Pi ? If not, maybe they have a different oscillator in place ? You probably find that setting in /boot/config.txt.

I have only tested this with a Rapsberry Pi 3 and a Raspberry Pi Zero W so far.

Do you have a picture of the scope-trace on GPIO4 output ?

[hzeller]

You can also try to comment out the { 7, 216.0e6 } by adding // in front and see if that fixes it.

[TheGuv]

Thanks!
HDMI is indeed enabled at whatever the default resolution is.
I can provide a picture if needed, but it's a sensible looking square-wave at 1.611 KHz.
I commented out { 7, 216.0e6 } to see and now it's generating 54KHz so your hunch about the HDMI clock may be close :)

[TheGuv]

I took a guess based on the rounded ratio of 1.611kHz and 60kHz and changed line 120 to { 7, 5.8e6 } and bingo 60kHz generated and my clocks set. rapidly.

[hzeller]

Wonderful, glad you got your watch setting.

I leave this bug open for now as we need to find a definitive source somewhere that describes the clock-sources for the older Pi you have, so that things can be automatically switched in this code. For now, I added a reference to this bug in the README.

[TheGuv]

Sounds OK to me. If I come across the information needed I'll report the details here.
Thanks again!

[gerardpalk]

Hi Henner and Steve
I had exactly the same issue as Steve using the Raspberry Zero W. Fixed as suggested. I live in Australia where we don't have a Radio Time Signal. So I now have a MSF clock running on perfect time. I will never have an excuse to be late for work. Thanks so much for your contribution Henner; and Steve for helping to come up with a solution. Gerard

[hzeller]

I still try to understand in which case this happens. Did you have connected a monitor by any chance? I suspect that might influence the hdmi oscillator.

[gerardpalk]

Yes, the monitor was connected at the time.

[JohnCGibbons]

I am running a RaspberryPi 3B+ with the latest Raspbian (ver 4.19.66-v7+) and using the -s wwvb option (I'm in the U.S.A.) the square waves generated on the GPIO pins 4 and 17 are exactly 1.6114 KHz or 1611.4 Hz. Hmmmm....

I was using an external HDMI display so I removed the display and tried re-booting the unit headless and now
----> I DO GET THE 60.000 KHz signal out on the GPIO pins! <-----

So having the HDMI display hooked up must grab and set the divider frequency and prevent you from setting it to what you want.

Conclusion: Run the unit headless and VNC into it.

Hope this helps.

John N8OBJ

[cdwijs]

I have a Rasperry Pi 3 model B+.
I have an HDMI connector connected displaying 1920x1080, I think at 60 Hz, and also got 2.081KHz.
Next I commented out line 114, and recompiled. //{ 7, 216.0e6 }, // HDMI
https://github.com/hzeller/txtempus/blob/master/gpio.cc#L114

Now I see in the console :getting 77500.227 Hz, and on my scope I see 77.74Khz

Cheers,
Cedric

[veselch]

Greetings!
First of all, I want to say thank you very much for this guide and program. Everything works great, without any errors. Even despite my crooked hands.

But there is one problem ... This is even most likely a feature of the watch, or something else, I don’t know ...
The fact is that with manual synchronization, when I start TXTEMPUS, and press the button on the clock to synchronize, they begin to receive a signal, after a minute the arrow starts to show a high (H) signal level. And after a few minutes, the synchronization completes successfully.

But, if I run this program at night, when the clock synchronizes in automatic mode, they cannot receive the signal and are not synchronized. The arrow shows RX and does not indicate H (high), M (middle) or L (low) level of signal.

Watch: citizen eco drive e650
Raspberry Pi model 3B+

Maybe someone faced a similar problem. I would really appreciate answers.

[hzeller]

you probably want to open a separate issue with this as it doesn't fit the frequency topic.