#include <SPI.h>
#include <OPL2.h>

OPL2 opl2;
unsigned char midiCmd[3];

void setup() {
  opl2.init();
  Serial.begin(1250000);
  // Sync with the 16u2
  Serial.write(0xfd);
  while (Serial.read() != 0xfd);
}

void loop() {
  // We assume only 0x9n commands will be sent
  if (Serial.available() < 3)
    return;

  Serial.readBytes(midiCmd, 3);

  if ((midiCmd[0] & 0xf0) != 0x90) {
    // Error (push reset button)
    opl2.reset();
    SPI.end();
    pinMode(LED_BUILTIN, OUTPUT);
    for (;;) {
      digitalWrite(LED_BUILTIN, HIGH);
      delay(500);
      digitalWrite(LED_BUILTIN, LOW);
      delay(500);
    }
  }

  // Signal to the 16u2 that a command was removed from the buffer
  Serial.write(0xf9);

  if (midiCmd[0] & 0x8) {
    // Reset OPL2
    opl2.reset();
    return;
  }

  opl2.write((midiCmd[0] << 7) | midiCmd[1], ((midiCmd[0] & 4) << 5) | midiCmd[2]);
}