Given a base frequency of 50Hz, which will include 'normal' harmonics (e.g. 100, 200Hz), we need to detect an embedded 58 Hz frequency. The 58 Hz may be as much as 70dB below the base frequency.
We require a C function (standard C) to run on an ARM processor which will take a pointer to an array of ADC values (14 bit integers justified to 16 bits), perform an FFT of your choice and write the relative amplitudes (rms values) back into the array.
The whole project can be developed on a PC BUT bear in mind, no system calls to the OS (we'll need to port it), typical RAM constraint will be 32K and most importantly no floating point processing (!). Real time updating in the order of once every 0.5 sec, so plenty of processing time available (at 50 Mhz).
The same scenario will be needed for 60Hz, 120 Hz and 380 Hz.
In a nutshell we need a spectrum analyser from say 40-400Hz with a few particular frequencies of interest (58 Hz, 68 Hz etc).
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I have 4 years of programming for embedded devices based on ARM processor using C. I also have expirience in low level code optimization. Ram constraints wll be fulfilled. Can do this job in in 5 days.