Steve Thackery wrote:
>>
>> But I have to ask, why would one need to compute an FFT in a PIC?
>
>Why not?  For the same reason you have to compute it in any other micro,
>surely?  Am I missing out on an alternative?
>
>I can't give full details of the project I'm working on, but in overview it's
>a tool for testing decay in telegraph poles by analysing the vibration
>spectrum from the pole when it is stimulated with an impulse.  The FFT is one
>stage in a fairly complex algorithm which produces a good/decayed indication.
>The algorithm was developed on a PC using Delphi, and then ported into a
>low-cost hand-held device.  Hence the use of a PIC.
>

Steve,

For the particular application you describe, you might actually be
farther ahead using a small notebook PC, possibly even a palmheld
using the (dreaded Microsoft) WindowsCE OS, with an A/D module
attached. The PC can perform all the complex algorithm processing
you will ever require, plus be able to permanently save data on HD
from 1000s of telephone poles for later analysis/archiving.

Plus, you can write s.w. in a high-level language on the PC that
will execute many times faster than highly-optimized assembler on
a PIC.

Seriously, the PIC may not be the best approach in this case. Its
limited internal RAM and inability to easily address external RAM,
plus its marginal computational power for DSP, are a serious
drawback to its use here.

best regards,
- Dan Michaels