ric-si11-parser.js

const EVENT_PACKET = 1;
const EVENT_ALARM = 2;

/**
 * Check if n-th bit set for number
 * @param value {number} number value
 * @param bit   {number} bit position
 */
function bit(value, bit) {
  return (value & (1 << bit)) !== 0;
}

/**
 * Parse Vega SI-11 Payload
 * https://en.iotvega.com/product/si11
 *
 * ```
 *                   | 0    | 1   | 2   | 3 | 4 | 5 | 6 | 7 | 8-11  | 12-15 | 16-19 | 20-23
 *  1 - EVENT_PACKET | type | bat | cfg |  timestamp    | t | in[0] | in[1] | in[2] | in[3]
 *  2 - EVENT_ALARM  | type | bat | cfg | i |   timestamp   | in[0] | in[1] | in[2] | in[3]
 * 
 * ```
 * @param payload {string} base64 encoded payload
 */
export function process(payload) {
  const data = ric.base64.decode(payload);
  let offset = 0;

  /* - option 1 - parse binary payload from raw byte array */
  const bytes = new Uint8Array(data.buffer);

  const evtype = bytes[offset++];
  const battery = bytes[offset++];
  const configByte = bytes[offset++];
  const config = {
    otaa: !bit(configByte, 0),
    abp: bit(configByte, 0),
    inputs: [
      +bit(configByte, 4),
      +bit(configByte, 5),
      // etc ...
    ],
  };
  const evin = evtype === EVENT_ALARM 
    ? bytes[offset++] 
    : undefined;

  /* - option 2 - use JS `DataView` interface (like Node's `Buffer`) */
  const evtime = data.getUint32(offset, true) * 1000;
  offset += 4;

  const temperature = evtype === EVENT_PACKET 
    ? data.getUint8(offset++) 
    : undefined;

  const inputs = [];
  for (let i = 0; i < 4; i++) {
    inputs[i] = data.getUint32(offset, true);
    offset += 4;
  }

  return { evtype, battery, config, evin, evtime, temperature, inputs };
}