Chuck Bass <email@example.com> wrote: : : I am looking for numerical routines to solve the following problem : : 1) Limited RAM (< 40 bytes available) : 2) Limited Processor (68HC11) : 3) Limited Time (real time app) : 4) Given a small number of samples (10?) determine if a given frequency : is present. : : Before I get a million FFT answers the following is important: I only : care about 1 frequency and a yes/no threshold detector result would be : OK (though a magnitude would be prefered ;->). Is there a very : efficient way to solve this? : : chuckb
Look at the Goertzel algorithm. This is a very simple way to compute the FFT in real time at a single frequency. It uses a second order IIR filter. Given your severe constraints, you probably will be limited to some kind of IIR filtering, but you may be able to use a higher order. The Goertzel algorithm is described in standard DSP texts such as Discrete Time Signal Processing by Oppenheim and Schafer, or the book by Proakis and Manolakis.