TTN Smart Sensor (Dezem)

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function uint16_BE(bytes, idx) { bytes = bytes.slice(idx || 0); return (bytes[0] << 8 | bytes[1] << 0); } function readVersion(bytes, idx) { bytes = bytes.slice(idx || 0); return "v" + bytes[0] + "." + bytes[1] + "." + bytes[2]; } function signed(val, bits) { if ((val & 1 << (bits - 1)) > 0) { // value is negative (16bit 2's complement) var mask = Math.pow(2, bits) - 1; val = (~val & mask) + 1; // invert all bits & add 1 => now positive value val = val * -1; } return val; } function int16_BE(bytes, idx) { bytes = bytes.slice(idx || 0); return signed(bytes[0] << 8 | bytes[1] << 0, 16); } // Decoder function for TTN function Decoder(bytes, port) { // Decode an uplink message from a buffer // (array) of bytes to an object of fields. var decoded = { "version": readVersion(bytes, 0), "shuntValue_Ohm": bytes[3] / 10, "amplifierGain": bytes[4], "vsysCurrent_mV": uint16_BE(bytes, 5) / 10, "vsysMin_mV": uint16_BE(bytes, 7) / 10, "vsysMax_mV": uint16_BE(bytes, 9) / 10, "vampRms_mV": uint16_BE(bytes, 11) / 10, "isecCurrent_mA": uint16_BE(bytes, 13) / 100, "isecAvgLong_mA": uint16_BE(bytes, 15) / 100, "isecAvgShort_mA": uint16_BE(bytes, 17) / 100, "isecMin_mA": uint16_BE(bytes, 19) / 100, "isecMax_mA": uint16_BE(bytes, 21) / 100, "measurmentsCounter": uint16_BE(bytes, 23), "lastUploadSec_sec": uint16_BE(bytes, 25), "temperature": int16_BE(bytes, 27) / 10, "powerlost": bytes[29] }; return decoded; }