
Clock calibration:

Roughly precalibrated with external frequency counter to get useful range for fine calibration

In loop 32 GRIs sampled and added together, no offset correction, searched for absolute maximum value in buffer.

"Tack" value is after how many normal cycled samples a "switch cycle" is inserted. 
Crystal on this board is too fast, switch cycles slow down.

Tack: 210  Maximum: 973
Tack: 211  Maximum: 1153
Tack: 212  Maximum: 1028
Tack: 213  Maximum: 958
Tack: 214  Maximum: 917
Tack: 215  Maximum: 844
Tack: 216  Maximum: 833
Tack: 217  Maximum: 1237
Tack: 218  Maximum: 1448
Tack: 219  Maximum: 1998
Tack: 220  Maximum: 2446
Tack: 221  Maximum: 2776
Tack: 222  Maximum: 2984
Tack: 223  Maximum: 3357
Tack: 224  Maximum: 3019
Tack: 225  Maximum: 3249
Tack: 226  Maximum: 3493
Tack: 227  Maximum: 3580
Tack: 228  Maximum: 3663  <-- Choose this ! "One switch cycle every 228 samples"
Tack: 229  Maximum: 3617
Tack: 230  Maximum: 3271
Tack: 231  Maximum: 3001
Tack: 232  Maximum: 2652
Tack: 233  Maximum: 2395
Tack: 234  Maximum: 1942
Tack: 235  Maximum: 1533
Tack: 236  Maximum: 1406
Tack: 237  Maximum: 1911
Tack: 238  Maximum: 1723
Tack: 239  Maximum: 1067

