My myriota Azure IoT Hub Cloud Identity Translation Gateway payload formatters uses C# code (compiled with CS-Script cached with Alastair Crabtrees’s LazyCache) to convert uplink packet payloads to JSON.
I have found that putting the C/C++ structure for the uplink payload at the top of the convertor really helpful.
/*
myriota tracker payload format
typedef struct {
uint16_t sequence_number;
int32_t latitude; // scaled by 1e7, e.g. -891234567 (south 89.1234567)
int32_t longitude; // scaled by 1e7, e.g. 1791234567 (east 179.1234567)
uint32_t time; // epoch timestamp of last fix
} __attribute__((packed)) tracker_message;
*/
using System;
using System.Collections.Generic;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
public class FormatterUplink : PayloadFormatter.IFormatterUplink
{
public JObject Evaluate(IDictionary<string, string> properties, string application, string terminalId, DateTime timestamp, JObject payloadJson, string payloadText, byte[] payloadBytes)
{
JObject telemetryEvent = new JObject();
telemetryEvent.Add("SequenceNumber", BitConverter.ToUInt16(payloadBytes));
double latitude = BitConverter.ToInt32(payloadBytes, 2) / 10000000.0;
telemetryEvent.Add("Latitude", latitude);
double longitude = BitConverter.ToInt32(payloadBytes, 6) / 10000000.0;
telemetryEvent.Add("Longitude", longitude);
UInt32 packetimestamp = BitConverter.ToUInt32(payloadBytes, 10);
DateTime lastFix = DateTime.UnixEpoch.AddSeconds(packetimestamp);
properties.Add("iothub-creation-time-utc", lastFix .ToString("s", CultureInfo.InvariantCulture));
return telemetryEvent;
}
}
The sample Tracker.cs payload formatter unpacks a message from Myriota Dev Kit running the Tracker sample and returns an Azure IoT Central compatible location telemetry payload.
BEWARE : I think the Azure IoT Central Position lat, lon + alt values might be case sensitive.
The identity payload formatter to use is configured as part of the Destination webhook Uniform Resource Locator (URL).
namespace devMobile.IoT.MyriotaAzureIoTConnector.Connector.Models
{
public class UplinkPayloadQueueDto
{
public string Application { get; set; }
public string EndpointRef { get; set; }
public DateTime PayloadReceivedAtUtc { get; set; }
public DateTime PayloadArrivedAtUtc { get; set; }
public QueueData Data { get; set; }
public string Id { get; set; }
public Uri CertificateUrl { get; set; }
public string Signature { get; set; }
}
public class QueueData
{
public List<QueuePacket> Packets { get; set; }
}
public class QueuePacket
{
public string TerminalId { get; set; }
public DateTime Timestamp { get; set; }
public string Value { get; set; }
}
}
A pair of Azure Blob Storage containers are used to store the uplink/downlink (coming soon) formatter files. The compiled payload formatters are cached with Uplink/Downlink + Application (from the UplinkPayloadQueueDto) as the key.
The default uplink and downlink formatters used when there is no payload formatter for “Application” are configured in the application settings.
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