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Datacake D Zero
LoRaWAN
Datasheets
Guides
Access Gateway Metadata
Concept
You can access the global variable
normalizedPayload which contains the following metadata:1
{
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"deveui": string, // The device's DevEUI
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"port": number, // The message's port
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"counter": number,
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"frequency": number, // GHz
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"data_rate": string, // Data rate according to https://blog.dbrgn.ch/2017/6/23/lorawan-data-rates/
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"coding_rate": string,
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"gateways": [
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"id": string,
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"datetime": date,
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"channel": number,
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"rssi": number,
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"snr": number
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]
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}
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This data is extracted from the LoRaWAN Network Server as being forwarded to Datacake over the Webhook. This information is normalized, meaning no matter whether you use TTN, TTI, Loriot, ChirpStack, or Wanesy, the information is always equally available and always formatted in the same way.
Raw Metadata
If you rather want to access the raw payload received from the LNS, you can do so via the global
rawPayload variable.Please note that when you access the
rawPayload, the information is not normalized and the content of rawPayload looks different between different LoRaWAN Network Server!Example Usage
In the following snippet, you find an example of how to read the Metadata from your Payload and how to bring that into your Datacake Payload Decoder section.
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function Decoder(payload, port) {
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// Output normalized Payload
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console.log(JSON.stringify(normalizedPayload,0,4));
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// Output raw payload coming from webhook of your LNS
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console.log(JSON.stringify(rawPayload,0,4));
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// Extract RSSI and Data-Rate from normalized Payload:
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// As being "normalized" this works between all LNS:
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// Including safety check so that these values really exist
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var LORA_RSSI = (!!normalizedPayload.gateways && !!normalizedPayload.gateways[0] && normalizedPayload.gateways[0].rssi) || 0;
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var LORA_SNR = (!!normalizedPayload.gateways && !!normalizedPayload.gateways[0] && normalizedPayload.gateways[0].snr) || 0;
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var LORA_DATARATE = normalizedPayload.data_rate;
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// extract timestamp from gateway
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var ts = rawPayload.recvTime; // Kerlink Wanesy
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// use normalized payload - NOTE: must have at least one Gateway!
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var ts = normalizedPayload.gateways[0]["datetime"];
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// Build up an array that can be used to forward it onto Datacake:
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var decoded = [
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{
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field: "LORA_RSSI",
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value: LORA_RSSI,
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timestamp: ts
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},
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{
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field: "LORA_DATARATE",
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value: LORA_DATARATE,
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timestamp: ts
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}
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];
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return decoded;
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}
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Create corresponding fields in Database
In order to store those Metadata-Fields, you can create new Fields on your Device and have historical Data for each field that you forward and store. Here is how this looks for the above example:
​
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