Ability to use media keys with Pico over USB HID

Final working code:

let debug = 0;
let code = 0;
let timeout;
let lastTime;

const VOLUME_UP    = 16712445;
const VOLUME_DOWN  = 16750695;
const PLAY_PAUSE   = 16754775;
const MUTE         = 16720605;
const NEXT         = 16748655;
const PREV         = 16769055;
const STOP         = 16756815;

E.setUSBHID({
  reportDescriptor : [
  0x05, 0x0c,  // USAGE_PAGE (Consumer Devices)
  0x09, 0x01,  // USAGE (Consumer Control)
  0xa1, 0x01,  // COLLECTION (Application)
               // -------------------- common global items
  0x15, 0x00,  //   LOGICAL_MINIMUM (0)
  0x25, 0x01,  //   LOGICAL_MAXIMUM (1)
  0x75, 0x01,  //   REPORT_SIZE (1)    - each field occupies 1 bit
               // -------------------- misc bits
  0x95, 0x05,  //   REPORT_COUNT (5)
  0x09, 0xb5,  //   USAGE (Scan Next Track)
  0x09, 0xb6,  //   USAGE (Scan Previous Track)
  0x09, 0xb7,  //   USAGE (Stop)
  0x09, 0xcd,  //   USAGE (Play/Pause)
  0x09, 0xe2,  //   USAGE (Mute)
  0x81, 0x06,  //   INPUT (Data,Var,Rel)  - relative inputs
               // -------------------- volume up/down bits
  0x95, 0x02,  //   REPORT_COUNT (2)
  0x09, 0xe9,  //   USAGE (Volume Up)
  0x09, 0xea,  //   USAGE (Volume Down)
  0x81, 0x02,  //   INPUT (Data,Var,Abs)  - absolute inputs
               // -------------------- padding bit
  0x95, 0x01,  //   REPORT_COUNT (1)
  0x81, 0x01,  //   INPUT (Cnst,Ary,Abs)
  0xc0         // END_COLLECTION
  ]
});

function p(c, cb) {
  E.sendUSBHID([c]);
  setTimeout(function() {
    E.sendUSBHID([0]);
    cb();
  },100);
}

next = function (cb) {
  p(0x1, cb);
  console.log('next');
};
prev = function (cb) {
  p(0x2, cb);
  console.log('prev');
};
stop = function (cb) {
  p(0x4, cb);
  console.log('stop');
};
playpause = function (cb) {
  p(0x8, cb);
  console.log('playpause');
};
mute = function (cb) {
  p(0x10, cb);
  console.log('mute');
};
volumeUp = function (cb) {
  p(0x20, cb);
  console.log('volumeUp');
};
volumeDown = function (cb) {
  p(0x40, cb);
  console.log('volumeDown');
};

const cb = () => {};

function handleCode() {
  timeout = undefined;
  if (debug) print(code);
  LED2.write(true);

  if (code === PLAY_PAUSE)  playpause(cb);
  if (code === VOLUME_UP)   volumeUp(cb);
  if (code === VOLUME_DOWN) volumeDown(cb);
  if (code === MUTE)        mute(cb);
  if (code === NEXT)        next(cb);
  if (code === PREV)        prev(cb);
  if (code === STOP)        stop(cb);

  code = 0;
  LED2.write(false);
}

// When an IR pulse is detected
function onPulseOn(e) {
  code = (code * 2) | (e.time - lastTime > 0.0008);
  if (timeout !== undefined) clearTimeout(timeout);
  timeout = setTimeout(handleCode, 20);
  lastTime = e.time;
}

// When IR pulse stops
function onPulseOff(e) {
  lastTime = e.time;
}

setWatch(onPulseOff, A5, { repeat: true, edge: "rising" });
setWatch(onPulseOn, A5, { repeat: true, edge: "falling" });

setWatch(
  // Press the button on the pico to enable debug mode and
  // see the IR code for your own remote
  function (e) {
    debug = !debug;
    console.log(`Debug mode ${debug ? "on" : "off"}`);
  },
  BTN,
  { repeat: true }
);