Initial commit

.gitignore

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+.pio
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch

.vscode/extensions.json

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+{
+    // See http://go.microsoft.com/fwlink/?LinkId=827846
+    // for the documentation about the extensions.json format
+    "recommendations": [
+        "platformio.platformio-ide"
+    ],
+    "unwantedRecommendations": [
+        "ms-vscode.cpptools-extension-pack"
+    ]
+}

include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the usual convention is to give header files names that end with `.h'.
+It is most portable to use only letters, digits, dashes, and underscores in
+header file names, and at most one dot.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

lib/README

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+
+This directory is intended for project specific (private) libraries.
+PlatformIO will compile them to static libraries and link into executable file.
+
+The source code of each library should be placed in a an own separate directory
+("lib/your_library_name/[here are source files]").
+
+For example, see a structure of the following two libraries `Foo` and `Bar`:
+
+|--lib
+|  |
+|  |--Bar
+|  |  |--docs
+|  |  |--examples
+|  |  |--src
+|  |     |- Bar.c
+|  |     |- Bar.h
+|  |  |- library.json (optional, custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html
+|  |
+|  |--Foo
+|  |  |- Foo.c
+|  |  |- Foo.h
+|  |
+|  |- README --> THIS FILE
+|
+|- platformio.ini
+|--src
+   |- main.c
+
+and a contents of `src/main.c`:
+```
+#include <Foo.h>
+#include <Bar.h>
+
+int main (void)
+{
+  ...
+}
+
+```
+
+PlatformIO Library Dependency Finder will find automatically dependent
+libraries scanning project source files.
+
+More information about PlatformIO Library Dependency Finder
+- https://docs.platformio.org/page/librarymanager/ldf.html

platformio.ini

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+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:teensylc]
+platform = teensy
+board = teensylc
+framework = arduino
+lib_deps = 
+	thomasfredericks/Bounce2@^2.71
+build_flags = -D USB_MIDI -D TEENSY_OPT_FASTEST

src/main.cpp

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+#include <Arduino.h>
+#include <Bounce2.h>
+
+#define MIDI_NAME {'P', 'i', 'n', 'g', 'b', 'o', 'a', 'r', 'd'}
+#define MIDI_NAME_LEN 9
+
+#define CHECK_PINS 9
+#define KEY_PINS 6
+#define BOUNCE_TIME 5
+#define POWER_SUPPLY_CHECK_PIN 13
+
+#define NUMBER_OF_KEYS 49
+#define SELF_DRIVE_INTERVAL 100
+
+Bounce check_pins[CHECK_PINS] {
+  {14, BOUNCE_TIME}, // not KEYS1..6
+  {15, BOUNCE_TIME}, // not KEYS7..12
+  {16, BOUNCE_TIME}, // not KEYS13..18
+  {17, BOUNCE_TIME}, // not KEYS19..24
+  {18, BOUNCE_TIME}, // not KEYS25..30
+  {19, BOUNCE_TIME}, // not KEYS31..36
+  {20, BOUNCE_TIME}, // not KEYS37..42
+  {21, BOUNCE_TIME}, // not KEYS43..48
+  {22, BOUNCE_TIME}  // not KEYS49
+};
+
+// not KEY0%6..not KEY5%6
+const unsigned char key_pins[KEY_PINS] {2, 3, 4, 5, 6, 7};
+// Array of pressed keys (initially all 0)
+bool keys_pressed[NUMBER_OF_KEYS];
+// K1, K2, K3, K4, K5, K12, K13, K14, K15
+const unsigned char self_drive_pins[CHECK_PINS] {8, 9, 10, 11, 12, 26, 23, 24, 25};
+volatile unsigned char curr_self_drive_pin = 0;
+IntervalTimer self_drive_timer = IntervalTimer();
+
+// Map the current array and pressed key to a MIDI note
+unsigned char mapToMidi(char curr_arr, char key) {
+  unsigned char offset = (curr_arr >> 1) * 12;
+  // TODO: maybe we have to switch the notes and array offsets
+  // Uneven offset are the upper octave, even the lower
+  if (curr_arr & 1) {
+    switch (key) {
+      case 0: return offset + 42; // F#2 + offset
+      case 1: return offset + 43; // G2 + offset
+      case 2: return offset + 44; // G#2 + offset
+      case 3: return offset + 45; // A2 + offset
+      case 4: return offset + 46; // A#2 + offset
+      case 5: return offset + 47; // B2 + offset
+    }
+  } else {
+    switch (key) {
+      case 0: return offset + 36; // C2 + offset
+      case 1: return offset + 37; // C#2 + offset
+      case 2: return offset + 38; // D2 + offset
+      case 3: return offset + 39; // D#2 + offset
+      case 4: return offset + 40; // E2 + offset
+      case 5: return offset + 41; // F2 + offset
+    }
+  }
+
+  // We hopefully never get here
+  return 0;
+}
+
+// Check if any of the array pins fell since last time
+char findCurrentArrPin() {
+  for (unsigned char i = 0; i < CHECK_PINS; i++) {
+    // Update status
+    check_pins[i].update();
+    // Check if the pin fell or is low
+    // ! inverted
+    if (check_pins[i].fell()) return i;
+  }
+
+  // If none fell we should have enough time to see which one is low
+  for (unsigned char i = 0; i < CHECK_PINS; i++) {
+    if (check_pins[i].read() == LOW) return i;
+  }
+
+  // Default return
+  return -1;
+}
+
+// Set the next self drive pin
+void nextSelfDrivePin() {
+  // Set the current pin to high
+  digitalWriteFast(self_drive_pins[curr_self_drive_pin], HIGH);
+  // Set the next pin
+  curr_self_drive_pin = (curr_self_drive_pin + 1) % CHECK_PINS;
+}
+
+// Interrupt for power supply check
+void powerStateChanged() {
+  unsigned char state = digitalReadFast(POWER_SUPPLY_CHECK_PIN);
+  // ! inverted
+  if (state == LOW) {
+    curr_self_drive_pin = 0;
+    self_drive_timer.begin(nextSelfDrivePin, SELF_DRIVE_INTERVAL);
+  } else {
+    self_drive_timer.end();
+  }
+}
+
+// Initial start function
+void setup() {
+  // Set all in- and outputs
+  for (unsigned char i = 0; i < CHECK_PINS; i++) {
+    pinMode(check_pins[i].getPin(), INPUT);
+    pinMode(self_drive_pins[i], INPUT);
+  }
+  for (unsigned char i = 0; i < KEY_PINS; i++) {
+    pinMode(key_pins[i], INPUT);
+  }
+  pinMode(POWER_SUPPLY_CHECK_PIN, INPUT);
+  // Manual call, so we can set the initial state
+  powerStateChanged();
+  // Setup interrupt for power supply
+  attachInterrupt(POWER_SUPPLY_CHECK_PIN, []() { while (true); }, CHANGE);
+}
+
+// Main loop
+void loop() {
+  // Find active arr pin
+  char curr_arr = findCurrentArrPin();  
+
+  // If none is active, we do nothing, else we check the keys
+  if (curr_arr >= 0) {
+    // Get all the key values ans send the MIDI message if needed
+    unsigned char value;
+    
+    for (unsigned char i = 0; i < KEY_PINS; i++) {
+      value = digitalReadFast(key_pins[i]);
+      // If the key is pressed, we send a MIDI message and set the entry in the array
+      // ! inverted
+      if (value == LOW) { 
+        // Check if the key is not already pressed
+        if (keys_pressed[curr_arr * 6 + i] == 0) {
+          // Send MIDI message
+          usbMIDI.sendNoteOn(mapToMidi(curr_arr, i), 127, 1);
+          // Set the entry in the array
+          keys_pressed[curr_arr * 6 + i] = 1;
+        }
+      } else {
+        // Check if the key is not already released
+        if (keys_pressed[curr_arr * 6 + i] == 1) {
+          // Send MIDI message
+          usbMIDI.sendNoteOff(mapToMidi(curr_arr, i), 0, 1);
+          // Set the entry in the array
+          keys_pressed[curr_arr * 6 + i] = 0;
+        }
+      }
+    }
+  }  
+
+  // MIDI Controllers should discard incoming MIDI messages.
+  while (usbMIDI.read()) {
+  }
+}

test/README

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+
+This directory is intended for PlatformIO Test Runner and project tests.
+
+Unit Testing is a software testing method by which individual units of
+source code, sets of one or more MCU program modules together with associated
+control data, usage procedures, and operating procedures, are tested to
+determine whether they are fit for use. Unit testing finds problems early
+in the development cycle.
+
+More information about PlatformIO Unit Testing:
+- https://docs.platformio.org/en/latest/advanced/unit-testing/index.html