DTMF tone generation

Oldbitcollector (Jeff)

This might be better asked in the current frequency generation thread, but has anyone done any DTMF (touch tone) generation with the prop yet?

Oldbitcollector

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The comments and code above are proof that a million monkeys with a million propeller chips *could* write Shakespeare!

fish

Oldbitcollector,
Are you making a accoustical dialer or an analog phone simulator?
http://nemesis.lonestar.org/reference/telecom/signaling/dtmf.html·(tons of info on the net)
I haven't seen any objects for DTMF, nor tried this myself, but it·seems like it would be·a trivial thing to do.
Just generate two simulatious tones at the specified freqs and voila.
You could make the spin object and submit it and be the first DTMF object author.

Good luck
fish

Beau Schwabe

fish,

For DTMF to work "properly" the two DTMF frequencies need to have a sinewave characteristic. Simply combining the two appropriate square waves
will produce so much noise, that a DTMF detector may not be able to discriminate the actual signal from the noise.

That said, the Propeller is fully capable of generating an appropriate signal. Heck, the BS2 is able to do this by generating a pseudo-sine wave with a small RC filter.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.