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i'm trying to decode infrared signal recorded with the saleae. It makes me wonder why saleae shows so low values for the frequencies from 0.1kHz to 0.8kHz. I found that standard for the IR is around 38kHZ. Is there something wrong with my record? Or did i misread the sample? enter image description here

closed as off-topic by per1234, MatsK, gre_gor, VE7JRO, Juraj Mar 29 '18 at 11:31

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about Arduino, within the scope defined in the help center." – per1234, MatsK, gre_gor, VE7JRO, Juraj
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    If you are using an IR receiver with 3 pins that is designed for a carrier frequency of 38kHz, then your will receive the logic signal only. If you use a photo transistor with 2 pins, then you should be able to see the carrier frequency along with a lot of noise. – Kwasmich Mar 20 '18 at 9:21
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What you are looking now is NOT the IR frequency, but the de-modulated signal.

Here is what I'm talking about:

Image description here

(image taken from http://www.electronicwings.com/sensors-modules/ir-communication)

As you can see, the various pulses are made of smaller pulses.

In your case you are seeing what is here called "Serial data", which is different from the carrier frequency. What the saleae board is telling you is that the width of the high part is 1.625ms, while the width of the low part is 0.631 ms; as you can see, the waveform is NOT periodic, so the "frequency" is meaningless (it's the reverse of the time marked on the view, which is the sum of one large high value and one low value).

Your plot resembles the NEC protocol (see for instance here). A logic '0' is a 562.5µs pulse followed by a 562.5µs space, while the logic '1' is a 562.5µs pulse burst followed by a 1.6875ms space (this is similar to by 0.631 ms and 1.625 ms measurement)

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