EuphonistiHack is a software developer for Texas Instruments but has a passion to play around with hardware. So after building a frequency analyzer using 8×8 LED array he moved on and built more advanced one. This time he used 320×240 16-bit color display with resistive touchscreen. First of all he took care of signal input. All he did was adding DC bias to audio signal so it would swing between ground and 3.3V. Probably some filtering capability wouldn’t hurt.
Frequency analyzer has some nice features and functions. Firs of all it allows to select signal frequency range from 4kHz up to 26kHz. This is achieved with timer triggered ADC sampling. FFT is calculated on 2048 point audio data. DSP calculations are performed using CMSIS DSP library – this is somewhat industry standardized way of doing this. Touch screen capability is used to select output parameters of signal. These include minimum and maximum frequencies, sampling frequency, number of bars and other information like debug and visual effect. LCD refresh rate can be adjusted up to 30 FPS at compile time. In video above results look really impressive.