piclist 2004\04\27\162157a >
Thread: Looking for an AVR FFT tutorial
www.piclist.com/techref/logic/dsps.htm?key=fft
picon face BY : Kenneth Lumia email (remove spam text)



>         What I want to design is an 8 or 16 tone AFSK modem.
>         With the Goertzel algorithm I can do the decoding in less
> than 20mS using the same ATMega8 running at 8MHz. My doubt is if
> the FFT process would give me advantages such as decoding speed
> or better error rate.

Mark,

Timeout.  Just as a side note, you may want to rethink using an ATmega8 to
build a working 8 or 16 tone AFSK modem (assuming you want it to work
in the "real" world).  There is just not enough horsepower there to do
a good enough job.  Specifically, have you thought about the baud rate
(and sampling/processing time required) for the receiver, the equalizer and
tap updates that go with it, the AGC, phase corrector, jitter tracker,
slicer
and the transmitter side including txfilter.  Oh and if it is supposed to be
2-wire,
don't forget the near and far end echo cancellers and their tap updates.
Way too much runtime.

Note that the above is not meant to dishearten your desire to learn, but
just a dose of datacom reality.

Ken

{Original Message removed}
<003601c42c95$1c13b7a0$0801a8c0@kl600> 7bit

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