This page contains the payload decoder and test data for the Zenner Easy Protect smoke detector RWM3 for integration into The Things Network (TTN). More information about the product and the decoder is also available on our german YouTube channel part 1 and part 2.

Decoder Script

The decoder was developed based on the payload documentation provided by the manufacturer. The script was tested with two smoke detectors in TTNs LoRaWAN network. In addition, the decoder always provides a Boolean value (smoke_detection) about a smoke alarm with True/False in addition to various status information.

/**
 * Decoder for Zenner smoke detector (Easy Protect Rauchwarnmelder RWM3)
 * More information: https://www.aeq-web.com/zenner-smoke-detector-rauch-warn-melder-3-payload-decoder/
 * Version 1.2
 */
function Decoder(bytes, port) {
 
    var packet = bytes[0];
    var packetType = (packet >> 4) & 0x0F;
    var packetSubtype = packet & 0x0F;
    var smokeDetection = false;
    var packetMessage = "unkown";
 
    if (packetType == 9) {
 
        if (packetSubtype == 2) {
            var firmwareVersion = "V" + bytes[4] + "." + bytes[3] + "." + bytes[2]
            var lorawanVersion = "V" + bytes[7] + "." + bytes[6] + "." + bytes[5]
            var lorawanCmdVersion = "V" + bytes[9] + "." + bytes[8]
            packetMessage = "SP9_02 (startup)";
 
            return_data = {
                message: packetMessage,
                firmware_version: firmwareVersion,
                lorawan_version: lorawanVersion,
                lw_comand_version: lorawanCmdVersion,
                smoke_detection: smokeDetection
            }
        } else if (packetSubtype == 1 && (bytes[1] == convertToDec("CA") || bytes[1] == convertToDec("CE"))) {
            //LoRaWAN com. scenario
            if (bytes[1] == convertToDec("CA")) {
                packetMessage = "Smoke alarm via LoRaWAN is disabled";
            } else if (bytes[1] == convertToDec("CE")) {
                packetMessage = "Smoke alarm via LoRaWAN is enabled";
            } else {
                packetMessage = "unkown message";
            }
 
            return_data = {
                message: packetMessage,
                smoke_detection: smokeDetection
            }
        } else if (packetSubtype == 1) {
 
            var dateTime = convertDateTime(bytes[4], bytes[3], bytes[2], bytes[1]);
            var statusCode = bytes[6] << 8 | bytes[5];
 
            packetMessage = "SP9_01 (status)";
 
            return_data = {
                message: packetMessage,
                datetime: dateTime,
                status: statusCode,
                smoke_detection: smokeDetection
            }
        } else {
 
            packetMessage = "SP9 (unkown subtype)";
 
            return_data = {
                message: packetMessage,
                smoke_detection: smokeDetection
            }
        }
 
    } else if (packetType == 1) {
 
        var mValue = bytes[4] << 24 | bytes[3] << 16 | bytes[2] << 8 | bytes[1];
        packetMessage = "SP1 (daily message)";
 
        return_data = {
            message: packetMessage,
            value: mValue,
            smoke_detection: smokeDetection
        }
    } else if (packetType == convertToDec("A")) {
 
        var eventDate = convertDate(bytes[4], bytes[3]);
 
 
        if (bytes[1] == convertToDec(19)) {
            smokeDetection = true;
            packetMessage = "Smoke detection alarm";
        } else if (bytes[1] == convertToDec(2)) {
            packetMessage = "Smoke detector removed from holder";
        } else if (bytes[1] == convertToDec("1C")) {
            packetMessage = "Object close to the sensor";
        }
 
        return_data = {
            message: packetMessage,
            date: eventDate,
            smoke_detection: smokeDetection
        }
    } else if (bytes[0] == convertToDec("FE") && bytes[1] == convertToDec(92)) {
 
        packetMessage = "Message via LoRaWAN will be sent when smoke detection triggers";
 
        return_data = {
            message: packetMessage,
            smoke_detection: smokeDetection
        }
    } else {
 
        return_data = {
            error: "Packet type is unkown!"
        }
    }
 
    function convertToDec(b) {
        var return_value = parseInt(b, 16);
        return return_value;
    }
 
    function convertDate(b0, b1) {
        var day = "0" + (b1 & 0x1F);
        var mon = "0" + (b0 & 0x0F);
        var year = ((b1 & 0xE0) >> 5) | ((b0 & 0xF0) >> 1);
        var date = day.substr(-2) + "-" + mon.substr(-2) + "-20" + year;
        return date;
    }
 
    function convertDateTime(b0, b1, b2, b3) {
        var day = "0" + (b1 & 0x1F);
        var mon = "0" + (b0 & 0x0F);
        var year = ((b1 & 0xE0) >> 5) | ((b0 & 0xF0) >> 1);
        var hour = "0" + (b2 & 0x1F);
        var min = "0" + (b3 & 0x3F);
        var datetime = day.substr(-2) + "-" + mon.substr(-2) + "-20" + year + " " + hour.substr(-2) + ":" + min.substr(-2);
        return datetime;
    }
 
    return return_data
}

Payload test data

The following payload data sets were recorded from a smoke detector and can be tested with the payload simulator at TTN:

Initial activation status packet:

921C001402020001200008FFFFFFFF0000

a01900ec29

Smoke alarm feedback via LoRaWAN is on:

91ca00

Smoke alarm feedback via LoRaWAN is off:

91ce00

Feedback after activation of LoRaWAN alarm packet (DL: 92CE0064A1) :

FE92