Fixed ADC ISR, calibration, and temporary disabled DSP filtering

@regularPolygon as you can see in the pull request title, I temporary disabled the DSP filtering taking place in the ADC interrupt service routine due to slowly down the code a lot. I was only able to sample the ADCs at 7.5 kHz with the filtering rather than the required 10 kHz. This fixed the sampling rate issue but we need to work out the issues with the filtering.

Closes #7