Has anyone used Siglib? Answer a question on the FFTr function? I'm hoping someone - anyone can answer a question on the Siglib library call to perform an FFT on data.

There's no examples anywhere I can find that provide a real application using data from an ADC, so that's where my wheels are spinning. 
The examples from Numerix have only canned data, generated by the function SDA_SignalGenerate. Specifically, in the FFT example, SDA_SignalGenerate is passed a value of $0.15625$ for frequency. Can anyone provide some insight as to what this represents? The FFT_LENGTH of the FFT function is $512$, but I do not see what the SDA_SignalGenerate frequency of $0.15625$ means, or what it is normalized to.

Thanks for any help anyone can provide.
This is the frequency normalized by the sampling frequency, i.e. in your case the frequency in Hz is

$$f=0.15625\cdot f_s$$

where $f_s$ is the sampling frequency in Hz. This can also be found in the SigLib reference manual (p. 251).