 int periods[] = {
   0,
   0,
+  0,
+  0,
+  0,
+  0,
+  0,
   0
 };
 
 // head positions (by drive)
 byte positions[] = {
+  0,
+  0,
+  0,
+  0,
+  0,
   0,
   0,
   0

int ticks[] = {
  0,
  0,
  0
};

// serial command codes
enum {
  MESSAGE_READY = 000,
  MESSAGE_INVALID = 001,
  MESSAGE_ACTIVE = 010,
  MESSAGE_RESET_ALL = 011,

const int FREQUENCY_MAX = 494;

// number of drives
const byte DRIVE_COUNT = 8;

// starting direction pin
const byte STARTING_PIN = 22;
// we assume direction pins occur on evens and step pins occur on odds
// (so for drive 0, direction is pin 2 and step is pin 3)

