mksmartevpacket.js

function crc16 (buf) {
  var crc = 0xffff;
  var i;
  var c;
  var len = buf.length;
  var start = 0;
  while (len--) {
    c = buf[start];
    for (i = 0; i < 8; i++) {
      if ((crc ^ c) & 1) {
        crc = (crc >> 1) ^ 0x8408;
      } else {
        crc >>= 1;
      }
      c >>= 1;
    }
    start++;
  }
  crc = (crc ^ 0xFFFF);
  return crc;
}

var escapeChars = [];
[0x11, 0x12, 0x13, 0x7e, 0x7D].forEach(function(ch) {
  escapeChars[ch] = 1;
});

function hldlcEscape(data) {
  var result = [0x7e];
  for (var i=0; i < data.length; ++i) {
    if (escapeChars[data[i]]) {
      result.push(0x7D);
      result.push(data[i] ^ 0x20);
    } else {
      result.push(data[i]);
    }
  }
  result.push(0x7e);
  return Buffer(result);
}

function makeEVSEpacket (amps) {
  var res = new Buffer('ff03500101036fbacf4159861c3da1437b3e2056', 'hex');
  res.writeFloatLE(amps/3, 6);
  var crc = crc16(res.slice(0, 18));
  res.writeUInt16LE(crc, 18);
  return hldlcEscape(res);
}

return {
  payload: makeEVSEpacket(msg.payload)
}