Yet another Arduino-based stepper motor MIDI synthesizer
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#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 long TickController::NextTick() {
return NextTickWithTs(timer2.get_count());
}
unsigned long TickController::NextTickWithTs(unsigned long cur_half_micros) {
if (period_with_bend == 0) {
return 0;
}
return cur_half_micros + period_with_bend;
}
MotorControl::MotorControl(int pin_dir, int pin_step) :
pin_dir(pin_dir), pin_step(pin_step),
next_tick_half_micros(0)
{
// No actual constructor logic -- initialization is in Init()
}
void MotorControl::Init() {
// Initialize the pin state
pinMode(pin_dir, OUTPUT);
pinMode(pin_step, OUTPUT);
digitalWrite(pin_dir, LOW);
digitalWrite(pin_step, LOW);
}
void MotorControl::TickOn(unsigned long period_half_micros) {
tick_ctrl.SetPeriod(period_half_micros);
// Notes below A4: rotate clockwise
// Notes above A4: rotate anticlockwise
// Notes are in units of __half micros__
digitalWrite(pin_dir, period_half_micros < 2300 * 2);
// Delay every note for 5 ms to add a bit of gap (attack) between notes
// 5 ms should be short enough (you need > 700 bpm for 1/64 notes to be 5ms long)
next_tick_half_micros = tick_ctrl.NextTick() + (unsigned long) 5 * 1000 * 2;
}
void MotorControl::TickAtPitch(unsigned int midi_pitch) {
// Bounds check
if (midi_pitch < midi_pitch_offset || midi_pitch >= midi_pitch_max) {
return;
}
TickOn(pgm_read_dword_near(midi_pitch_period + (midi_pitch - midi_pitch_offset)));
}
void MotorControl::TickPitchBend(int bend) {
// Note: the Arduino MIDI library re-positions bend to [-8192, 8192) instead of the default [0, 16384)
// we need to correct for this here
bend = bend - MIDI_PITCHBEND_MIN;
if (bend < 0 || bend >= 16384) return;
tick_ctrl.SetBend(bend);
// We don't need to re-calculate next tick here, because if a note is currently on,
// it will eventually call NextTick() anyway
}
void MotorControl::TickOff() {
tick_ctrl.SetPeriod(0);
next_tick_half_micros = tick_ctrl.NextTick();
}
void MotorControl::Tick(unsigned long cur_half_micros) {
if (next_tick_half_micros == 0) {
return;
}
if (cur_half_micros >= next_tick_half_micros) {
DoTick();
next_tick_half_micros = tick_ctrl.NextTickWithTs(cur_half_micros);
}
}
void MotorControl::DoTick() {
// Pulse the step pin once
digitalWrite(pin_step, HIGH);
digitalWrite(pin_step, LOW);
}