Lowest power tune detector.

[Ian Stirling]

I'd like a keyring that responds to a whistled tune, rather than a
simple tone, for better noise rejection.
One way is to attach my laptop to my keyring, run a FFT over the output
of the mic, and then look for spikes in the correlation of the tune
with the historical output of the FFT. Needless to say this uses too
much power, and is a bit bulky.
Another would be to go analog, have several tuned filters outputting to
comparators/ADCs, but this has a high component count.
This is to go into another device, which has a 3.3V supply.
I'd like it to draw under 150uA or so.

Are there micros that can do this?
ADC at ~8Khz, clocking at a few tens of Khz, and do the MAC thing for
maybe 8 tones?

 

[Luhan]

I'd like a keyring that responds to a whistled tune, rather than a
simple tone, for better noise rejection.

Are there micros that can do this?
ADC at ~8Khz, clocking at a few tens of Khz, and do the MAC thing for
maybe 8 tones?

Maybe a low power op amp on the mic providing a logic level output to a
PIC in sleep mode. The PIC wakes up on any noise and does FFT to check
for the tone. PIC12F675 is a good choise, very low current in sleep
mode and 10-bit a/d for the tone input. Run the whole thing on a 3
volt watch battery.

Luhan

 

[John Jardine.]

I'd like a keyring that responds to a whistled tune, rather than a
simple tone, for better noise rejection.
One way is to attach my laptop to my keyring, run a FFT over the output
of the mic, and then look for spikes in the correlation of the tune
with the historical output of the FFT. Needless to say this uses too
much power, and is a bit bulky.
Another would be to go analog, have several tuned filters outputting to
comparators/ADCs, but this has a high component count.
This is to go into another device, which has a 3.3V supply.
I'd like it to draw under 150uA or so.

Are there micros that can do this?
ADC at ~8Khz, clocking at a few tens of Khz, and do the MAC thing for
maybe 8 tones?

Your're pretty much looking at a multi tone telemetry system. The 60's
sounding rockets needed racks full of equipment to do similar. Even now
you'll need some -heavy- signal massaging using quite a powerful DSP/Micro.
Small PICs won't touch it. FFTs' are way over the top. Need to be using
something like the Goertzel algorithm.
john

 

[Luhan]

Your're pretty much looking at a multi tone telemetry system. The 60's
sounding rockets needed racks full of equipment to do similar. Even now
you'll need some -heavy- signal massaging using quite a powerful DSP/Micro.
Small PICs won't touch it. FFTs' are way over the top. Need to be using
something like the Goertzel algorithm.

Wrong you are. I have DTMF decoder implemented in a PIC. Its been
answering my phone calls for a couple of years now, so I know it works.

Check it out at...

http://members.cox.net/berniekm/qdft.html

Luhan

 

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I'd like a keyring that responds to a whistled tune, rather than a
simple tone, for better noise rejection.

Do you have perfect pitch, or will your device be responding to
intervals rather than absolute frequencies?