fixes bug with some keyboards that do send mysterious note-off events

noteblock.ino

-#include "MIDIUSB.h"
+#include "MIDIUSB.h" // see https://github.com/arduino-libraries/MIDIUSB
 #include <math.h>
 
 #define DEBUG
@@ -14,10 +14,10 @@
 int16_t notes[NUM_VALVES] = {-1, -1, -1};
 
 // array of the length of the tone period required to create the tone
-uint16_t period[NUM_VALVES] = {0, 0, 0};
+uint16_t periods[NUM_VALVES] = {0, 0, 0};
 
 // array of the current state of the valve pins (for tone periods)
-uint8_t state[NUM_VALVES] = {0, 0, 0};
+uint8_t states[NUM_VALVES] = {0, 0, 0};
 
 // array for the period timer helpers
 uint64_t lastNoteMicros[NUM_VALVES] = {0, 0, 0};
@@ -66,22 +66,32 @@ uint16_t midi2frq(uint8_t number) {
 }
 
 // puts the note into the notes array or removes it if already present
-uint8_t putNote(int8_t note) {
+int8_t putNote(int8_t note, uint8_t state) {
   // set note
-  for (int8_t i = 0; i < NUM_VALVES; i++) {
-    if (notes[i] == -1) { // note on
+  for (uint8_t i = 0; i < NUM_VALVES; i++) {
+    if (notes[i] == -1 && state == 1) { // note on
       notes[i] = note;
       return i;
-    } else if (notes[i] == note) { // note off
-      notes[i] = -1;
-      for (int8_t j = i; j < NUM_VALVES - 1; j++) {
+    } else if (notes[i] == note && state == 0) { // note off
+      //notes[i] = -1;
+      for (uint8_t j = i; j < NUM_VALVES - 1; j++) {
         notes[j] = notes[j + 1];
+        periods[j] = periods[j + 1];
+        states[j] = states[j + 1];
+        lastNoteMicros[j] = lastNoteMicros[j + 1];
       }
       notes[NUM_VALVES - 1] = -1;
+      periods[NUM_VALVES - 1] = 0;
+      states[NUM_VALVES - 1] = 0;
+      lastNoteMicros[NUM_VALVES - 1] = 0;
       return i;
     }
   }
 
+  if (state == 0) {
+    return -1;
+  }
+
   // remove oldest note and shift other notes
   for (int8_t i = 0; i < NUM_VALVES - 1; i++) {
     notes[i] = notes[i + 1];
@@ -92,9 +102,10 @@ uint8_t putNote(int8_t note) {
 }
 
 void loop() {
+  // handle USB MIDI IN
   midiEventPacket_t rx;
   rx = MidiUSB.read();
-  if (rx.header != 0) {
+  if (rx.byte1 != 0) {
     #ifdef DEBUG
       char buffer[256];
       sprintf(buffer, "header: 0x%X  b1: %d  b2: %d  b3: %d", rx.header, rx.byte1,
@@ -102,24 +113,24 @@ void loop() {
       Serial.println(buffer);
     #endif
 
-    if ((rx.header & 0x09) == 0x09) { // handle note on
-      uint8_t noteIdx = putNote(rx.byte2);
+    if ((rx.byte1 & 0xF0) == 0x90 && rx.byte3 > 0) { // handle note on
+      int8_t noteIdx = putNote(rx.byte2, 1);
       uint16_t frq = midi2frq(rx.byte2);
 
-      period[noteIdx] = 1000000 / frq / 2;
+      periods[noteIdx] = 1000000 / frq / 2;
 
       #ifdef DEBUG
         Serial.println("ONNNNNNN " + String(rx.byte2) + " @ " + String(noteIdx));
       #endif
-    } else if ((rx.header & 0x08) == 0x08) { // handle note off
+    } else if ((rx.byte1 & 0xF0) == 0x80 || ((rx.byte1 & 0xF0) == 0x90 && rx.byte3 == 0)) { // handle note off
       #ifdef DEBUG
         int8_t idx = 0;
       #endif
 
       for (int8_t i = 0; i < NUM_VALVES; i++) {
         if (notes[i] != -1 && notes[i] == rx.byte2) {
-          putNote(rx.byte2);
-          period[i] = 0;
+          putNote(rx.byte2, 0);
+          //periods[i] = 0;
 
           #ifdef DEBUG
             idx = i;
@@ -147,10 +158,10 @@ void loop() {
 
   // check for notes that require attention
   for (uint8_t i = 0; i < NUM_VALVES; i++) {
-    if (lastNoteMicros[i] + period[i] < nowMicros && notes[i] != -1) {
+    if (lastNoteMicros[i] + periods[i] < nowMicros && notes[i] != -1) {
       lastNoteMicros[i] = nowMicros;
-      state[i] ^= 1;
-      digitalWrite(valves[i], state[i]);
+      states[i] ^= 1;
+      digitalWrite(valves[i], states[i]);
     } else if (notes[i] == -1) { // be sure to end notes that should be ended
       digitalWrite(valves[i], LOW);
     }