public static void Main()
{
    DateTime sasTokenValidUntilUtc = DateTime.UtcNow;

    Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} devMobile.IoT.RAK.Wisblock.AzureIoTHub.RAK11200.PowerConservation starting");

    Configuration.SetPinFunction(Gpio.IO04, DeviceFunction.I2C1_DATA);
    Configuration.SetPinFunction(Gpio.IO05, DeviceFunction.I2C1_CLOCK);

    if (!WifiNetworkHelper.ConnectDhcp(Config.Ssid, Config.Password, requiresDateTime: true))
    {
        if (NetworkHelper.HelperException != null)
        {
             Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} WifiNetworkHelper.ConnectDhcp failed {NetworkHelper.HelperException}");
        }

        Thread.Sleep(Timeout.Infinite);
    }

    string uri = $"{Config.AzureIoTHubHostName}.azure-devices.net/devices/{Config.DeviceID}";

    // not setting Authorization here as it will change as SAS Token refreshed
    HttpClient httpClient = new HttpClient
    {
        SslProtocols = System.Net.Security.SslProtocols.Tls12,
        HttpsAuthentCert = new X509Certificate(Config.DigiCertBaltimoreCyberTrustRoot),
        BaseAddress = new Uri($"https://{uri}/messages/events?api-version=2020-03-13"),
    };

    I2cConnectionSettings settings = new(I2cDeviceBusID, Shtc3.DefaultI2cAddress);
    I2cDevice device = I2cDevice.Create(settings);
    Shtc3 shtc3 = new(device);

    AdcController adcController = new AdcController();
    AdcChannel batteryChargeAdcChannel = adcController.OpenChannel(AdcControllerChannel);

    string sasToken = "";

    while (true)
    {
        DateTime standardisedUtcNow = DateTime.UtcNow;

        Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub device {Config.DeviceID} telemetry update start");

        if (sasTokenValidUntilUtc <= standardisedUtcNow)
        {
            sasTokenValidUntilUtc = standardisedUtcNow.Add(Config.SasTokenRenewEvery);

            sasToken = SasTokenGenerate(uri, Config.Key, sasTokenValidUntilUtc);

            Debug.WriteLine($" Renewing SAS token for {Config.SasTokenRenewFor} valid until {sasTokenValidUntilUtc:HH:mm:ss dd-MM-yy}");
        }

        if (!shtc3.TryGetTemperatureAndHumidity(out var temperature, out var relativeHumidity))
        {
            Debug.WriteLine($" Temperature and Humidity read failed");

            continue;
        }

        double batteryCharge = batteryChargeAdcChannel.ReadRatio() * 100.0;

        Debug.WriteLine($" Temperature {temperature.DegreesCelsius:F1}°C Humidity {relativeHumidity.Value:F0}% BatteryCharge {batteryCharge:F1}%");

        string payload = $"{{\"RelativeHumidity\":{relativeHumidity.Value:F0},\"Temperature\":{temperature.DegreesCelsius.ToString("F1")}, \"BatteryCharge\":{batteryCharge:F1}}}";

        try
        {
            using (HttpContent content = new StringContent(payload))
            {
                content.Headers.Add("Authorization", sasToken);

                using (HttpResponseMessage response = httpClient.Post("", content))
                {
                    Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Response code:{response.StatusCode}");

                    response.EnsureSuccessStatusCode();
                 }
            }
        }
        catch (Exception ex)
        {
            Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub POST failed:{ex.Message} {ex?.InnerException?.Message}");
        }

        Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub telemetry update done");

        Thread.Sleep(Config.TelemetryUploadInterval);
    }
}

public static void Main()
{
    Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} devMobile.IoT.RAK.Wisblock.AzureIoTHub.RAK11200.PowerSleep starting");

    Thread.Sleep(5000);

    try
    {
        Configuration.SetPinFunction(Gpio.IO04, DeviceFunction.I2C1_DATA);
        Configuration.SetPinFunction(Gpio.IO05, DeviceFunction.I2C1_CLOCK);

        Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Wifi connecting");

        if (!WifiNetworkHelper.ConnectDhcp(Config.Ssid, Config.Password, requiresDateTime: true))
       {
            if (NetworkHelper.HelperException != null)
            {
                 Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} WifiNetworkHelper.ConnectDhcp failed {NetworkHelper.HelperException}");
            }

            Sleep.EnableWakeupByTimer(Config.FailureRetryInterval);
            Sleep.StartDeepSleep();
        }

        Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Wifi connected");

        // Configure the SHTC3 
        I2cConnectionSettings settings = new(I2cDeviceBusID, Shtc3.DefaultI2cAddress);
        I2cDevice device = I2cDevice.Create(settings);
        Shtc3 shtc3 = new(device);

        // Assuming that if TryGetTemperatureAndHumidity fails accessing temperature or relativeHumidity will cause an exception
        shtc3.TryGetTemperatureAndHumidity(out var temperature, out var relativeHumidity);

#if SLEEP_SHT3C
        shtc3.Sleep();
#endif

        // Configure Analog input (AIN0) port then read the "battery charge"
        AdcController adcController = new AdcController();
        AdcChannel batteryChargeAdcChannel = adcController.OpenChannel(AdcControllerChannel);

        double batteryCharge = batteryChargeAdcChannel.ReadRatio() * 100.0;

        Debug.WriteLine($" Temperature {temperature.DegreesCelsius:F1}°C Humidity {relativeHumidity.Value:F0}% BatteryCharge {batteryCharge:F1}");

        // Assemble the JSON payload, should use nanoFramework.Json
        string payload = $"{{\"RelativeHumidity\":{relativeHumidity.Value:F0},\"Temperature\":{temperature.DegreesCelsius.ToString("F1")}, \"BatteryCharge\":{batteryCharge:F1}}}";

        // Configure the HttpClient uri, certificate, and authorization
        string uri = $"{Config.AzureIoTHubHostName}.azure-devices.net/devices/{Config.DeviceID}";

        HttpClient httpClient = new HttpClient()
        {
            SslProtocols = System.Net.Security.SslProtocols.Tls12,
            HttpsAuthentCert = new X509Certificate(Config.DigiCertBaltimoreCyberTrustRoot),
            BaseAddress = new Uri($"https://{uri}/messages/events?api-version=2020-03-13"),
        };
        httpClient.DefaultRequestHeaders.Add("Authorization", SasTokenGenerate(uri, Config.Key, DateTime.UtcNow.Add(Config.SasTokenRenewFor)));

        Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub device {Config.DeviceID} telemetry update start");

        HttpResponseMessage response = httpClient.Post("", new StringContent(payload));

        Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Response code:{response.StatusCode}");

        response.EnsureSuccessStatusCode();
    }
    catch (Exception ex)
    {
        Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub telemetry update failed:{ex.Message} {ex?.InnerException?.Message}");

        Sleep.EnableWakeupByTimer(Config.FailureRetryInterval);
        Sleep.StartDeepSleep();
    }

    Sleep.EnableWakeupByTimer(Config.TelemetryUploadInterval);
#if SLEEP_LIGHT
    Sleep.StartLightSleep();
#endif
#if SLEEP_DEEP
    Sleep.StartDeepSleep();
#endif
 }

public static void Main()
{
   DateTime sasTokenValidUntilUtc = DateTime.UtcNow;

   Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} devMobile.IoT.RAK.Wisblock.AzureIoHub.RAK1901.SasKey starting");

...         
   string uri = $"{Config.AzureIoTHubHostName}.azure-devices.net/devices/{Config.DeviceID}";

   // not setting Authorization here as it will change as SAS Token refreshed
   _httpClient = new HttpClient
   {
      SslProtocols = System.Net.Security.SslProtocols.Tls12,
      HttpsAuthentCert = new X509Certificate(Config.DigiCertBaltimoreCyberTrustRoot),
      BaseAddress = new Uri($"https://{uri}/messages/events?api-version=2020-03-13"),
   };

   I2cConnectionSettings settings = new(I2cDeviceBusID, Shtc3.DefaultI2cAddress);
   I2cDevice device = I2cDevice.Create(settings);
   Shtc3 shtc3 = new(device);

   string sasToken = "";

   while (true)
   {
      DateTime standardisedUtcNow = DateTime.UtcNow;

      Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub device {Config.DeviceID} telemetry update start");

      if (sasTokenValidUntilUtc <= standardisedUtcNow)
      {
         sasTokenValidUntilUtc = standardisedUtcNow.Add(Config.SasTokenRenewEvery);

         sasToken = SasTokenGenerate(uri, Config.Key, sasTokenValidUntilUtc);

         Debug.WriteLine($" Renewing SAS token for {Config.SasTokenRenewFor} valid until {sasTokenValidUntilUtc:HH:mm:ss dd-MM-yy}");
      }

      if (!shtc3.TryGetTemperatureAndHumidity(out var temperature, out var relativeHumidity))
      {
         Debug.WriteLine($" Temperature and Humidity read failed");

         continue;
      }

      Debug.WriteLine($" Temperature {temperature.DegreesCelsius:F1}°C Humidity {relativeHumidity.Value:F0}%");

      string payload = $"{{\"RelativeHumidity\":{relativeHumidity.Value:F0},\"Temperature\":{temperature.DegreesCelsius.ToString("F1")}}}";

      try
      {
         using (HttpContent content = new StringContent(payload))
         {
            content.Headers.Add("Authorization", sasToken);

            using (HttpResponseMessage response = _httpClient.Post("", content))
            {
               Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Response code:{response.StatusCode}");

               response.EnsureSuccessStatusCode();
            }
         }
      }
     catch (Exception ex)
     {
         Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub POST failed:{ex.Message} {ex?.InnerException?.Message}");
      }

      Debug.WriteLine($"{DateTime.UtcNow:HH:mm:ss} Azure IoT Hub telemetry update done");

      Thread.Sleep(Config.TelemetryUploadInterval);
   }
}

public class Config
{
   public const string DeviceID = "RAK11200-RAK19001";
   public const string AzureIoTHubHostName = "...";
   public const string Key = "...";
   public readonly static TimeSpan SasTokenRenewFor = new TimeSpan(24, 0, 0);
   public readonly static TimeSpan SasTokenRenewEvery = new TimeSpan(0, 30, 0);
   public readonly static TimeSpan TelemetryUploadInterval = new TimeSpan(0, 10, 0);

   public const string Ssid = "Orcon-Wireless";
   public const string Password = "160220502280";
...
}

public static string SasTokenGenerate(string resourceUri, string key, DateTime sasKeyTokenUntilUtc)
{
   long sasKeyvalidUntilUtcUnix = sasKeyTokenUntilUtc.ToUnixTimeSeconds();

   string stringToSign = $"{HttpUtility.UrlEncode(resourceUri)}\n{sasKeyvalidUntilUtcUnix}";

   var hmac = SHA.computeHMAC_SHA256(Convert.FromBase64String(key), Encoding.UTF8.GetBytes(stringToSign));

   string signature = Convert.ToBase64String(hmac);

   return $"SharedAccessSignature sr={HttpUtility.UrlEncode(resourceUri)}&sig={HttpUtility.UrlEncode(signature)}&se={sasKeyvalidUntilUtcUnix}";
}