Like most of my posts regarding nanoFramework and the M5Core2, I owe a debt to those who created this stuff and I’m really just going through some of the samples etc. Trying them out and documenting my findings. This post is no different, it’s based on the Welcome to the .NET nanoFramework WebServer repository

Add the NuGet package nanoFramework.WebServer to your nanoFramework project.

You’ll need to also include code to connect to your WiFi, so checkout my post on that subject – Wifi using nanoFramework on the M5Core2.

Assuming you’ve connected to your WiFi, we can set up a WebServer like this

using var server = new WebServer(80, HttpProtocol.Http, new[] { typeof(PowerController) });
server.Start();

Thread.Sleep(Timeout.Infinite);

The first line supplies an array of controllers, so you can have multiple controllers for your different endpoints. In this case we’ve just got the single controller PowerController. This is a simple class that includes RouteAtrribute and MethodAttribute adorned methods to acts as routes/endpoints.

Let’s look at the PowerController, which just returns some M5Core2.Power values when accessed via http://m5core2_ip_address/power.

public class PowerController
{
   [Route("power")]
   [Method("GET")]
   public void PowerRoute(WebServerEventArgs e)
   {
      var power = M5Core2.Power;
           
      var sb = new StringBuilder();
      sb.AppendLine("Power:");
      sb.AppendLine($"  Adc Frequency: {power.AdcFrequency}");
      sb.AppendLine($"  Adc Pin Current: {power.AdcPinCurrent}");
      sb.AppendLine($"  Adc Pin Current Setting: {power.AdcPinCurrentSetting}");
      sb.AppendLine($"  Adc Pin Enabled: {power.AdcPinEnabled}");
      sb.AppendLine($"  Batt. Temp. Monitor: {power.BatteryTemperatureMonitoring}");
      sb.AppendLine($"  Charging Current: {power.ChargingCurrent}");
      sb.AppendLine($"  Charging Stop Threshold: {power.ChargingStopThreshold}");
      sb.AppendLine($"  Charging Voltage: {power.ChargingVoltage}");
      sb.AppendLine($"  Dc Dc1 Voltage: {power.DcDc1Voltage.Millivolts} mV");
      sb.AppendLine($"  Dc Dc2 Voltage: {power.DcDc2Voltage.Millivolts} mV");
      sb.AppendLine($"  Dc Dc3 Voltage: {power.DcDc3Voltage.Millivolts} mV");
      sb.AppendLine($"  EXTEN Enable: {power.EXTENEnable}");
      sb.AppendLine($"  VOff Voltage: {power.VoffVoltage}");
      sb.AppendLine($"  Gpio0 Behavior: {power.Gpio0Behavior}");
      sb.AppendLine($"  Gpio0 Value: {power.Gpio0Value}");

      e.Context.Response.ContentType = "text/plain";
      WebServer.OutPutStream(e.Context.Response, sb.ToString());
}

As you can see from the last line of code, we send the response back with our payload, the string of power information.

We can also return HTTP codes using

WebServer.OutputHttpCode(e.Context.Response, HttpStatusCode.OK);

This is great, but what’s the IP address of our IoT device, so I can access the web server?

Well, ofcourse you could check your router or DHCP server, but better still, let’s output the IP address to the M5Core2 screen using

Console.WriteLine(IPGlobalProperties.GetIPAddress().ToString());

We can support multiple routes per method, such as

[ublic class PowerController
{
[Route("power")]
[Route("iotpower")]
[Method("GET")]
public void PowerRoute(WebServerEventArgs e)
{
// code removed
}

Note: Routes are usually case insensitive, unless you add the CaseSensitiveAttribute to your method.

The M5Core includes an accelerometer which allows us to measure the rate of acceleration, as well as a gyroscope to sense angular movement.

We initialize the combined AccelerometerGyroscope and calibrate it by using the following code. The number, 100 in this case, is the number of iterations to calibrate the AccelerometerGyroscope

M5Core2.AccelerometerGyroscope.Calibrate(100);

Let’s look at the code to read the accelerometer and gyroscope (we’ll also read the internal temperature of the AccelerometerGyroscope)

Console.Clear();

M5Core2.AccelerometerGyroscope.Calibrate(100);

while (true)
{
   var accelerometer = M5Core2.AccelerometerGyroscope.GetAccelerometer();
   var gyroscope = M5Core2.AccelerometerGyroscope.GetGyroscope();
   var temperature = M5Core2.AccelerometerGyroscope.GetInternalTemperature();

   Console.CursorLeft = 0;
   Console.CursorTop = 1;

   Console.WriteLine("Accelerator:");
   Console.WriteLine($"  x={accelerometer.X}");
   Console.WriteLine($"  y={accelerometer.Y}");
   Console.WriteLine($"  z={accelerometer.Z}");
   Console.WriteLine("Gyroscope:");
   Console.WriteLine($"  x={gyroscope.X}");
   Console.WriteLine($"  y={gyroscope.Y}");
   Console.WriteLine($"  z={gyroscope.Z}");
   Console.WriteLine("Internal Temp:");
   Console.WriteLine($"  Celsius={temperature.DegreesCelsius}");

   Thread.Sleep(20);
}

The nanoFramework comes with a Console class, for the M5Stack this is in the namespace nanoFramework.M5Stack.Console

Before we uses the Console we need to initialize the screen, this essentially creates the screen buffer and assigns a font from the application’s resource. As I’m testing this stuff on the M5Core2, the code looks like this.

M5Core2.InitializeScreen();

Now we can simply use the Console like we would for a Console application on Windows.

// clear the console
Console.Clear();

// output some test
Console.WriteLine("Some Text");

// change the foreground colour
Console.ForegroundColor = Color.Red;
Console.WriteLine("Some Red Text");

// change foreground and background colours
Console.BackgroundColor = Color.Yellow;
Console.ForegroundColor = Color.White;
Console.WriteLine("Some Green Text on Yellow Background");

We can also change the font by supplying a font resource, the default included is consolas_regular_16.tinyfnt. We would add the font as a resource and create the font like this

Console.Font = Resource.GetFont(Resource.FontResources.consolas_regular_16);

We can move the cursor around using

Console.CursorLeft = 3;
Console.CursorTop = 5;

We can also get the height and width of our window via the Console using

Console.WriteLine($"Height: {Console.WindowHeight}, Width: {Console.WindowWidth}");

In the previous post Wifi using nanoFramework on the M5Core2 we looked at connecting our M5Core2 using it’s wireless network capability, to our WiFi network. Next, let’s look at how we access a website, for example I’ll try to access the Cheer Lights API.

We’ll need to add the NuGet package nanoFramework.System.Net.Http.Client which exposes the HttpClient functionality for the nanoFramework.

Just like the full .NET framework/and core. We should create an HttpClient for the lifetime of the application. So we’d have something like this

public static class CheerLights
{
   private static readonly HttpClient HttpClient = new HttpClient();
}

The Cheer Lights API is a simple call to https://api.thingspeak.com/channels/1417/field/2/last.txt which will return a #hex colour, for example #008000. So. we might write some code, such as this in a funtion within the CheerLights class

var requestUri = "https://api.thingspeak.com/channels/1417/field/2/last.txt";

var response = HttpClient.Get(requestUri);
response.EnsureSuccessStatusCode();
var responseBody = response.Content.ReadAsString();

This would work for a non-HTTPS site, but for HTTPS requires that we get the CA certificate for the site we want to interact with (I haven’t yet found a way to use HTTPS without this).

To get the certificate, navigate to the page using a browser (I’m using Microsoft EDGE). Click on the padlock, click on connection is secure, then click on the show certificate button. Select Details then in the Certificate Hierarchy select the root CA certificate and export this (renaming as a txt file). This will be what we used for the HttpsAuthentCert (as we’ll see in a moment).

Now we want to include the certificate which we can do as a resource or just embedding the text into the code. So now we’d have something like this

try
{
   HttpClient.HttpsAuthentCert = new X509Certificate(
                        @"-----BEGIN CERTIFICATE-----
MIIDrzCCApegAwIBAgIQCDvgVpBCRrGhdWrJWZHHSjANBgkqhkiG9w0BAQUFADBh
MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3
d3cuZGlnaWNlcnQuY29tMSAwHgYDVQQDExdEaWdpQ2VydCBHbG9iYWwgUm9vdCBD
QTAeFw0wNjExMTAwMDAwMDBaFw0zMTExMTAwMDAwMDBaMGExCzAJBgNVBAYTAlVT
MRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5j
b20xIDAeBgNVBAMTF0RpZ2lDZXJ0IEdsb2JhbCBSb290IENBMIIBIjANBgkqhkiG
9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4jvhEXLeqKTTo1eqUKKPC3eQyaKl7hLOllsB
CSDMAZOnTjC3U/dDxGkAV53ijSLdhwZAAIEJzs4bg7/fzTtxRuLWZscFs3YnFo97
nh6Vfe63SKMI2tavegw5BmV/Sl0fvBf4q77uKNd0f3p4mVmFaG5cIzJLv07A6Fpt
43C/dxC//AH2hdmoRBBYMql1GNXRor5H4idq9Joz+EkIYIvUX7Q6hL+hqkpMfT7P
T19sdl6gSzeRntwi5m3OFBqOasv+zbMUZBfHWymeMr/y7vrTC0LUq7dBMtoM1O/4
gdW7jVg/tRvoSSiicNoxBN33shbyTApOB6jtSj1etX+jkMOvJwIDAQABo2MwYTAO
BgNVHQ8BAf8EBAMCAYYwDwYDVR0TAQH/BAUwAwEB/zAdBgNVHQ4EFgQUA95QNVbR
TLtm8KPiGxvDl7I90VUwHwYDVR0jBBgwFoAUA95QNVbRTLtm8KPiGxvDl7I90VUw
DQYJKoZIhvcNAQEFBQADggEBAMucN6pIExIK+t1EnE9SsPTfrgT1eXkIoyQY/Esr
hMAtudXH/vTBH1jLuG2cenTnmCmrEbXjcKChzUyImZOMkXDiqw8cvpOp/2PV5Adg
06O/nVsJ8dWO41P0jmP6P6fbtGbfYmbW0W5BjfIttep3Sp+dWOIrWcBAI+0tKIJF
PnlUkiaY4IBIqDfv8NZ5YBberOgOzW6sRBc4L0na4UU+Krk2U886UAb3LujEV0ls
YSEY1QSteDwsOoBrp+uvFRTp2InBuThs4pFsiv9kuXclVzDAGySj4dzp30d8tbQk
CAUw7C29C79Fv1C5qfPrmAESrciIxpg0X40KPMbp1ZWVbd4=
-----END CERTIFICATE-----");

   var requestUri = "https://api.thingspeak.com/channels/1417/field/2/last.txt";
   var response = HttpClient.Get(requestUri);
   response.EnsureSuccessStatusCode();
   var responseBody = response.Content.ReadAsString();

When we’re creating an IoT device, the likelihood is we’ll want to connect to Wifi and the internet (well it’s sort of in the IoT name isn’t it).

Please note, this post is heavily based upon the nanoFramework samples, so do go and view them for a whole host of excellent sample code.

The nanoFramework comes with a NuGet package named nanoFramework.System.Device.Wifi which you’ll need to add to your project.

Now we can use the WifiNetworkHelper class to connect to your DHCP server (your router generally) using the ConnectDhcp method. Now this will also save the configuration of the network ssid and password.

const string ssid = "YOUR_SSID";
const string password = "YOUR_WIFI_PASSWORD";

var cs = new CancellationTokenSource(60000);
var success = WifiNetworkHelper.ConnectDhcp(ssid, password, requiresDateTime: true, token: cs.Token);
if (!success)
{
    Debug.WriteLine($"Cannot connect to the WiFi, error: {WifiNetworkHelper.Status}");
    if (WifiNetworkHelper.HelperException != null)
    {
        Debug.WriteLine($"ex: {WifiNetworkHelper.HelperException}");
    }
}
else
{
   Debug.WriteLine("Connected successfully");
}

As mentioned, the ConnectDhcp method saves our configuration, so once that’s happened, we can switch to using the Reconnect method instead, i.e.

var cs = new CancellationTokenSource(60000);
var success = WifiNetworkHelper.Reconnect(requiresDateTime: true, token: cs.Token);
if (!success)
{
    Debug.WriteLine($"Cannot connect to the WiFi, error: {WifiNetworkHelper.Status}");
    if (WifiNetworkHelper.HelperException != null)
    {
        Debug.WriteLine($"ex: {WifiNetworkHelper.HelperException}");
    }
}
else
{
   Debug.WriteLine("Connected successfully");
}

The ssid and password are stored using the Wireless80211Configuration on the device. So we can check if our configuration has been stored – this ofcourse also means we can get access to the configuration – beware if security is an issue that these are then available as plain text

var configuration = Wireless80211Configuration.GetAllWireless80211Configurations();
foreach (var config in configuration)
{
   Debug.WriteLine($"SSID: {config.Ssid}, Password: {config.Password}");
}