Test to ensure DMA and ISR aren't mixing up electrode data.

[nhz2]

If there is a subtle bug with the DMA setup and or the ISR, some electrode data could get swapped. This needs to be tested, possibly by playing a signal on one of the ADC inputs will grounding the others and checking that it is accurately recorded. Another test could be done with the full setup by stimulating one electrode at a time with a known resistance.