motor_control: refactor: Extract TickController logic

While we are at it, fix the MIDI bend implementation so that it doesn't
reset every time a new note is played.

motor_control.cpp

@@ -1,12 +1,45 @@
 #include <Arduino.h>
 #include <midi_Defs.h>
+#include <eRCaGuy_Timer2_Counter.h>
 #include "motor_control.h"
 #include "./pitch_table.h"
 
+TickController::TickController() :
+    midi_bend(8192), period_half_micros(0), period_with_bend(0) {
+
+}
+
+void TickController::SetPeriod(unsigned int half_micros) {
+    period_half_micros = half_micros;
+    CalculatePeriod();
+}
+
+void TickController::SetBend(unsigned int bend) {
+    if (bend >= 16384) {
+        return;
+    }
+
+    midi_bend = bend;
+    CalculatePeriod();
+}
+
+void TickController::CalculatePeriod() {
+    if (period_half_micros == 0) {
+        period_with_bend = 0;
+        return;
+    }
+    // Scale the MIDI bend value down to 0 - 2047
+    unsigned int _bend = midi_bend / 8;
+    period_with_bend = (unsigned int) (((float) period_half_micros) * pgm_read_float_near(midi_pitch_bend_scale + _bend));
+}
+
+unsigned int TickController::GetTruePeriod() {
+    return period_with_bend;
+}
+
 MotorControl::MotorControl(int pin_dir, int pin_step) :
     pin_dir(pin_dir), pin_step(pin_step),
-    last_tick_half_micros(0), tick_period_half_micros(0),
-    tick_period_orig_half_micros(0)
+    last_tick_half_micros(0)
 {
     // No actual constructor logic -- initialization is in Init()
 }
@@ -20,9 +53,8 @@ void MotorControl::Init() {
 }
 
 void MotorControl::TickOn(unsigned long period_half_micros) {
-    tick_period_half_micros = period_half_micros;
-    tick_period_orig_half_micros = period_half_micros;
-    // Force the next tick to happen
+    tick_ctrl.SetPeriod(period_half_micros);
+    // Force a tick
     last_tick_half_micros = 0;
 }
 
@@ -41,29 +73,22 @@ void MotorControl::TickPitchBend(int bend) {
     bend = bend - MIDI_PITCHBEND_MIN;
     
     if (bend < 0 || bend >= 16384) return;
-    if (tick_period_orig_half_micros == 0) return;
-
-    // Scale the MIDI bend value down to 0 - 2047
-    bend = bend / 8;
-
-    tick_period_half_micros = (unsigned long) (((float) tick_period_orig_half_micros) * pgm_read_float_near(midi_pitch_bend_scale + bend));
+    
+    tick_ctrl.SetBend(bend);
 }
 
 void MotorControl::TickOff() {
-    tick_period_half_micros = 0;
-    tick_period_orig_half_micros = 0;
+    tick_ctrl.SetPeriod(0);
 }
 
 void MotorControl::Tick(unsigned long cur_half_micros) {
-    if (cur_half_micros == 0) {
+    unsigned long period = tick_ctrl.GetTruePeriod();
+
+    if (period == 0) {
         return;
     }
 
-    if (tick_period_half_micros == 0) {
-        return;
-    }
-
-    if (last_tick_half_micros == 0 || (cur_half_micros - last_tick_half_micros) >= tick_period_half_micros) {
+    if (last_tick_half_micros == 0 || cur_half_micros >= last_tick_half_micros + period) {
         DoTick();
         last_tick_half_micros = cur_half_micros;
     }

motor_control.h

@@ -1,15 +1,30 @@
 #pragma once
 
+class TickController {
+    private:
+        // 0 to disable
+        unsigned int period_half_micros;
+        // 0 - 16384, 8192 = no bend
+        unsigned int midi_bend;
+        unsigned int period_with_bend;
+        
+        void CalculatePeriod();
+
+    public:
+        TickController();
+        void SetPeriod(unsigned int half_micros);
+        void SetBend(unsigned int bend);
+        // In units of half microseconds
+        // 0 = disabled
+        unsigned int GetTruePeriod();
+};
+
 class MotorControl {
     private:
         // Control pins of the stepper motor
         int pin_dir, pin_step;
-        // Timestamp of the last motor tick
         unsigned long last_tick_half_micros;
-        // Interval of motor ticking; 0 to disable the motor
-        unsigned long tick_period_half_micros;
-        // Original period of motor ticking (without applying bend)
-        unsigned long tick_period_orig_half_micros;
+        TickController tick_ctrl;
 
         void DoTick();
     public: