Use unrolled loops to sample at 2MHz & 4MHz rates. Based on some
testing by Bob Davis (http://bobdavis321.blogspot.com)
The maximum with a 16MHz clock is 5.3333MHz (3 cycles per sample) but
sampling at that rate isn't very accurate. Accuracy is pretty good at
2MHz & 4MHz.
The Arduino Mega 2560 is now supported in addition to the regular
Arduino. The Mega supports 8 channels and 7k samples. The ols.profile-*
files are device profiles for the alternative SUMP client. 'AGLA' =
Arduino 'AGLAM' = Arduino Mega