mockband/MockBand.ino

#include <stdint.h>
#include <Arduino.h>
#include <PluggableUSB.h>

#include "hid.hh" // Modified HID library: doesn't prefix each packet with ID
#include "instrument.hh"

//#include "blue.hh"  // Ginnie's blue guitar
#include "standard.hh"  // Standard pins

// Maximum time between wammy bar updates.
#define UPDATE_INTERVAL_MS 20

// After an edge on a pin, stop listening for this long, to debounce it
#define SILENCE_INTERVAL_MS 40

// Your measured samples per frame, more or less
#define SAMPLES_PER_FRAME 127

// Some arithmetic for the compiler, to make the code fast
#define SAMPLES_PER_MS (SAMPLES_PER_FRAME / UPDATE_INTERVAL_MS)
#define SILENCE_SAMPLES (SAMPLES_PER_MS * SILENCE_INTERVAL_MS)

#if USB_VID != 0x1bad
#error USB_VID must be set to 0x1bad
#endif

#if USB_PID == 0x0004
#define GUITAR
#elif USB_PID == 0x0005
#define DRUM
#else
#error USB_PID must be set to 4 (Guitar) or 5 (Drum)
#endif

InstrumentButtonState buttonState;

void setup() {
  pinMode(STRUM_DOWN, INPUT_PULLUP);
  pinMode(STRUM_UP, INPUT_PULLUP);
  pinMode(TILT_SWITCH, INPUT_PULLUP);
  pinMode(BUTTON_GREEN, INPUT_PULLUP);
  pinMode(BUTTON_RED, INPUT_PULLUP);
  pinMode(BUTTON_YELLOW, INPUT_PULLUP);
  pinMode(BUTTON_BLUE, INPUT_PULLUP);
  pinMode(BUTTON_ORANGE, INPUT_PULLUP);
  pinMode(SOLO_GREEN, INPUT_PULLUP);
  pinMode(SOLO_RED, INPUT_PULLUP);
  pinMode(SOLO_YELLOW, INPUT_PULLUP);
  pinMode(SOLO_BLUE, INPUT_PULLUP);
  pinMode(SOLO_ORANGE, INPUT_PULLUP);
  pinMode(ANALOG_WAMMY, INPUT);
  pinMode(BUTTON_PLUS, INPUT_PULLUP);
  pinMode(BUTTON_MINUS, INPUT_PULLUP);

  // Initialize HID
  static HIDSubDescriptor node(_hidReportDescriptor, sizeof(_hidReportDescriptor));
  HID().AppendDescriptor(&node);  

  buttonState.axis[0] = 0;
  buttonState.axis[1] = 0;
  buttonState.axis[2] = 0;
  buttonState.axis[3] = 0;
  for (int i = 0; i < 12; i++) {
    buttonState.reserved1[i] = 0x0;
  }
  buttonState.finalConstant = 0x0200020002000200;
}

// Order of pins in sample
uint8_t pins[] = {
  BUTTON_BLUE,
  BUTTON_GREEN,
  BUTTON_RED,
  BUTTON_YELLOW,
  BUTTON_ORANGE,
  TILT_SWITCH,
  STRUM_UP,        // Not in USB packet
  STRUM_DOWN,      // Not in USB packet
  BUTTON_MINUS,
  BUTTON_PLUS,
  SOLO_BLUE,       // Not in USB packet
  SOLO_GREEN,      // Not in USB packet
  SOLO_RED,        // Not in USB packet
  SOLO_YELLOW,     // Not in USB packet
  SOLO_ORANGE,     // Not in USB packet
};
#define npins (sizeof(pins) / sizeof(*pins))

// The 3.3v Pro Micro is on the slow side.
// Our strategy is to poll button state as quickly as possible,
// and hope we don't miss anything while we're doing USB stuff.
void loop() {
  uint16_t buttons = 0;
  uint16_t samples = 0;
  unsigned long next = 0;
  uint16_t silence[npins] = {0};

  while (1) {
    unsigned long now = millis();
    uint16_t edge = 0;

    samples++;

    for (uint8_t i = 0; i < npins; i++) {
      if (silence[i]) {
        silence[i]--;
      } else if (bitRead(buttons, i) != !digitalRead(pins[i])) {
        edge |= bit(i);
        silence[i] = SILENCE_SAMPLES;
      }
    }
    buttons ^= edge;

    // We've sampled everything. Is it time to do calculations and USB?
    if (!edge && (next > now)) {
      continue;
    }
    next = now + UPDATE_INTERVAL_MS;
    
    buttonState.buttons = (buttons & 0b1100111111);      // All directly-mappable bits
    buttonState.buttons |= ((buttons >> 10) & 0b11111);  // Solo keys
    bitWrite(buttonState.buttons, 6, (buttons >> 10) & 0b11111); // Solo bit

    // I don't understand why any rational engineer would have done this.
    buttonState.hatAndConstant = (0x08
      ^ (bitRead(buttons, 6) << 4) // up
      // right << 3
      ^ (bitRead(buttons, 7) << 2) // down
      // left << 1
    );

    buttonState.axis[2] = analogRead(ANALOG_WAMMY) / 4;

    // The second Y axis doesn't appear to be used, so I'm logging sample rate with it
    buttonState.axis[3] = samples & 0xff;   // most things map this to [-1,1]

    // Send an update
    HID().SendReport(0, (uint8_t *)&buttonState, 27);

    samples = 0;
  }
}