MIDIfication of Church Organ Pedal Board

1#include <MIDIUSB.h>
2#include <ArduinoQueue.h>
3
4/*
5Program  for MIDIfying a 30-key organ pedal board with Arduino Due as Midi controller and  IR-sensors TCRT5000
6Original code by Prof. David Musker, June 2020
7Adapted  by Johannes Barkowsky, April 2022
8Free for use if source is acknowledged
9*/
10
11//=================================================================
12const  byte KeyboardSize = 30;                                  // size of pedalboard here  30 keys, can be set to 27, 25 or whatever
13const byte StartNotePin = 2;                                   //  first digital input pin for note lowest note is set to pin 2, leaving digital pin  1 and 0 for other use
14                                                               //  so 30 pins now are pin3 to 32. StartNotePin can be set to 5 or whatever. It moves  all pins up then.
15const byte NoteOff = B10000000;
16const byte NoteOn  = B10010000;
17
18const  byte MidiChannel = 3;                                    // 3 sets Midi channel  to channel 4; according to midi_Defs.h a 0 translates to MIDI_CHANNEL_OMNI, not  sure though
19const byte LowestNote = 24;                                    //  Midi note number of lowest note, set to C1
20
21const byte KeyPin [KeyboardSize]  = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29};
22
23//=================================================================
24unsigned  long KeyReadTime = 0;
25unsigned long DebounceTime = 20;                               //  20 ms in real life for notes - might be set lower
26unsigned long LastMIDISentTime;                                // track when last MIDI message sent
27unsigned  long MidiLag = 50;                                    // delay between MIDI messages  - greater than 25 ms and less than say 500 ms to avoid latency
28
29byte NoteCount  = 0;                                            // notes on
30byte NoteCountOld  = 0;                                         // notes on at last scan
31byte NotesChanged  = 0;                                         // note changes from last scan
32byte  Velocity;
33
34bool KeyState[KeyboardSize] = {true};                          //  orig. false, but set here to true, because IR-sensors are HIGH, when pedals are  up
35bool NoteState[KeyboardSize] [3] = {false};                    // current  and last note states and a change flag
36unsigned long KeyLastTime [KeyboardSize]  = {0};                // times since last key transitions
37
38//Queue creation:
39ArduinoQueue<midiEventPacket_t>  MidiChannelNoteQueue(20);      // 20 here is the maximum number of items
40
41//=================================================================
42void  setup () {
43delay(1000); // remedy for Arduino Due R3 startup reset issue - perhaps  unnecessary
44
45Serial.begin(31250); // MIDI transmission speed is 31250 baud
46  for (int i = 0; i < KeyboardSize; i++) {
47    pinMode((StartNotePin+i), INPUT_PULLUP);  // digital input pins with pullup resistor
48  }
49}
50
51//=================================================================
52void  loop () {
53
54KeyRead();
55NoteRead();
56NoteSend();
57TransmitMIDI();
58
59}  //main loop ends here
60
61//=================================================================
62void  KeyRead() {
63KeyReadTime = millis();
64  for (int i = 0; i < KeyboardSize; i++)  { // note reading loop
65    KeyState[i] = !digitalRead(KeyPin[i]+StartNotePin);  // indirect addressing via keypin array; keystate is here reversed (!), because  IR-sensors are HIGH by default
66  }
67}
68
69//=================================================================
70void  NoteRead() {
71NoteCountOld = NoteCount;
72NotesChanged = 0;
73 for (int i =  0; i < KeyboardSize; i++ ) { 
74  if ((KeyReadTime - KeyLastTime [i]) > DebounceTime)  { // only look at key state if it is more than DebounceTime since last change in  note, otherwise skip
75    KeyLastTime [i] = KeyReadTime;
76    NoteState[i][3]  = false;
77    NoteState[i][2] = NoteState[i][1]; // update previous note state
78    if (((KeyState[i] == false) && (NoteState[i][1] == true)) || ((KeyState[i] ==  true) && (NoteState[i][1] == false))){ // key state has changed
79        NoteState[i][1]  = KeyState[i]; // update current note state
80        NoteState[i][3] = true; //  set a changed state flag
81        NotesChanged++;
82        if (NoteState[i][1]  == true) { // note is on
83         NoteCount++; // increment number of notes on
84         }
85        else {NoteCount--;} // decrement number of notes on
86    }    
87   }
88  }
89}
90/*
91At the end of this loop, we have:
92NoteState[i][1]  - current note states, 
93NoteState[i][2] - previous note states, and 
94NoteState[i][3]  - change flags 
95NoteCount - a count of the number of notes ON
96NotesChanged  - a count of the number of notes changed 
97*/
98
99//=================================================================
100void  NoteSend() {
101if (NotesChanged > 0) { // something has changed
102    for (int  i = 0; i < (KeyboardSize); i++) {
103      if (NoteState[i][3] == true){ // note  state has changed
104        if (NoteState[i][1] == true){ // note is ON
105          sendNoteOn((i+  LowestNote), MidiChannel, 127); // velocity is here fixed at 127
106          }
107          else {
108            sendNoteOff((i+ LowestNote), MidiChannel, 0);} //  note is OFF
109            }
110      }
111   }
112}
113  
114//=================================================================
115void  sendNoteOn (byte Pitch, byte MidiChannel, byte Velocity) {
116  MIDImessage(NoteOn,  MidiChannel, Pitch, Velocity);
117}
118
119//=================================================================
120void  sendNoteOff (byte Pitch, byte MidiChannel, byte Velocity) {
121  MIDImessage(NoteOff,  MidiChannel, Pitch, Velocity);
122}
123
124//=================================================================
125void  MIDImessage(int byte1, int byte2, int byte3, int byte4) { // sends a 3 byte MIDI  message via the serial port and queues it
126  // one could use the Arduino Midi  library command instead
127  byte cmd = (byte1 + byte2);
128  Serial.write(cmd);  // send note on or note off command
129  Serial.write(byte3); // send pitch
130  Serial.write(byte4); //send velocity
131  midiEventPacket_t midiMsg = {cmd >>  4, cmd, byte3, byte4};
132  MidiChannelNoteQueue.enqueue(midiMsg);
133}
134
135//=================================================================
136void  TransmitMIDI() {
137if ((micros() - LastMIDISentTime) > MidiLag) { // send only  if the delay time has expired
138   if (!MidiChannelNoteQueue.isEmpty()) { // something  is in the main channel queue
139      MidiUSB.sendMIDI(MidiChannelNoteQueue.dequeue());
140      MidiUSB.flush();
141      LastMIDISentTime = micros();
142      }
143  }
144}
145