433MHz protocol modulation type

Developers
1

Hi there,

I am trying to implement a JUNG 433MHz ASK button which is currently used to control the lights of the hood in the kitchen.

I decoded the signal using Universal Radio Hacker with RTL-SDR USB-stick. And I was also able to create the correct signal-timings. So far everything seems good.

But my signals are not working. And I think I know what might be the problem. Here you can see what the original signal is, as registered by URH:

1
11908Ă—370 102 KB

This is what I created with Homey:

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21911Ă—345 47.7 KB

So far so good. But if you zoom in you see what I think is the problem.

Homey:

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31590Ă—155 22 KB

Original:

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41593Ă—173 46.7 KB

There seems to be some modulation happening in the original signal. In Homey, a single period is around 1us whereas in Homey it’s around 30us. Also one “interval” (I don’t know how else to call it) looks like this:
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(there is a slope on both sides).

I’ve tried fiddling around with the baudRate settings but I seem to be unable to configure Homey so it will behave as the example I provided.

Does anyone have any idea on if this is at all possible? Or if not, what I could do to make this work?

Thanks!
Peter

1 Like
2

Welcome on the forum,

The default modulation Homey uses is ASK
See https://apps-sdk-v2.developer.athom.com/tutorial-Signals.html
And the best analyser to get a signal definitions should be
https://developer.athom.com/tools/signals

Guess you should be able to edit your post and add the images now.

3

Thanks Dijker, I have now updated the original post and inlined the images!

I am aware that ASK is being used and that there is a signal-definition recorder on the developer page. Unfortunately, this recorder doesn’t seem to recognise this type of signal. I think this is because of two reasons:

  1. The signal is not the same as some other 433MHz devices in the sense that the other devices I’ve created an app for, are more repeating. As in the same signal is sent 20 times. With this device, the first message is different than the 3 repetitions that follow. Hence, I did register two messages.
  2. And as I’ve said in the initial post, the structure of the messages seem perfect, but there is some kind of modulation going on.

This doesn’t seem to be FSK either, since the frequency stays the same. It’s just that the frequency seems to be a bit higher (1us per sample vs 30us per sample) And that there is the modulation. Unfortunately shifting the carrier frequency in modulation.carrier doesn’t seem to help.