I downloaded a tone app for my iPhone and played 3 tones. I recorded the sound on the robot's microphone, and did a dft (the uC is a Cortex M4F and has DSP capabilities). I then uploaded the data out the UART and graphed them in Google sheets. It looks pretty good.

I use a complex DFT. It was also fast, but I was using a 128 float32, or 64 complex numbers (set phase to 0). Next steps are 1) coding beep communication between robots, and Android 2) coding cepstral coefficients for preparing to do word recognition.