firmata-electron/lib/onewireutils.js

A library to control an arduino running firmata

var Encoder7Bit = require("./encoder7bit");

var OneWireUtils = {
  crc8: function(data) {
    var crc = 0;

    for (var i = 0; i < data.length; i++) {
      var inbyte = data[i];

      for (var n = 8; n; n--) {
        var mix = (crc ^ inbyte) & 0x01;
        crc >>= 1;

        if (mix) {
          crc ^= 0x8C;
        }

        inbyte >>= 1;
      }
    }
    return crc;
  },

  readDevices: function(data) {
    var deviceBytes = Encoder7Bit.from7BitArray(data);
    var devices = [];

    for (var i = 0; i < deviceBytes.length; i += 8) {
      var device = deviceBytes.slice(i, i + 8);

      if (device.length !== 8) {
        continue;
      }

      var check = OneWireUtils.crc8(device.slice(0, 7));

      if (check !== device[7]) {
        console.error("ROM invalid!");
      }

      devices.push(device);
    }

    return devices;
  }
};

module.exports = OneWireUtils;