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Author Topic: Decoding CTCSS - Possible?  (Read 935 times)
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Hello,

I am currently building a repeater logic for a radio project and I have the need to decode CTCSS as an access method.

I've searched quite a lot and found no one doing it with the Arduino, only PIC and I don't know if that's an accurate reading or not. There is still hardware decoders out there but they are old and costs a lot, all the new radios today have all the options in one big IC.  smiley-razz

My first thought was to use the pulseIn() function and measure the input line via a low pass filter and a schmitt trigger but have not yet tested this theory. Do you think it's possible? Can the readings be accurate enough to not open on a nearby CTCSS frequency?

Maybe someone has a better idea? All answers are welcome!

Best regards,
Swoshie
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Quite possible, there is 48 notes recognition, which is pretty close:
http://coolarduino.wordpress.com/2011/09/03/arduino-musical-note-recognition-pushing-the-limits/
Better instead of UNO use Mega, more memory  'd not hurt. As messages "overlapped" with regular audio traffic (wiki says),  good quality LPF necessary, sharp 3-5 -th order, not ready to say if arduino could manage it or hardware / co-processor has to be
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I doubt that it can be done with an Arduino. In some cases the tones are only about 3Hz apart which would make it very difficult to distinguish them.

Pete
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Maybe try a Teensy 3.0? Give yourself a bit of extra processing power smiley
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Have you seen this?
http://www.embedded.com/design/connectivity/4025660/Detecting-CTCSS-tones-with-Goertzel-s-algorithm
Using that method the Teensy 3.0 should be able to do the job.

Pete
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