Both the Meadow F7 development board and SMT module have WiFi networking via the ESP32 co-processor. The Meadow F7 embedded SMT module also adds optional ethernet capabilities.

Current Beta Limitations

All SSL Certificates Accepted - SSL connections are supported, but currently, all certificates over TLS (https) are accepted without any validation.

Sample Apps

For example code, see the following networking sample apps in the Meadow.Core.Samples repo:

Wifi_Basics - Covers the basics of enumerating and connecting to WiFi networks.
HttpListener - Shows how to respond to HTTP requests with HttpListenerContext, HttpListenerRequest, and HttpListenerResponse.
Antenna Switching - Shows how to use the antenna API to switch between the onboard and external antenna connection.

WiFi

Initializing the `WiFiAdapter`

In order to use wifi networking, you must first initialize the WiFiAdpater by calling InitWiFiAdapter() on the F7Micro device:

Device.InitWiFiAdapter().Wait();

The intialization method can take 5 or more seconds, and is awaitable.

Once initialized, the WiFiAdapter is available as a property on the F7Micro class and can be accessed via the Device property in your app class:

// from within your app class:
Device.WiFiAdapter

// from other classes, where [MeadowApp] is the name of your app class:
[MeadowApp].Device.WiFiAdapter

Connecting to a WiFi Network

Once the WiFiAdapter has been initialized, you can connect to a network by calling the Connect method and passing in the SSID (network name), and password:

if (Device.WiFiAdapter.Connect("SSID", "Pass").ConnectionStatus != ConnectionStatus.Success) {
    throw new Exception("Cannot connect to network, applicaiton halted.");
}

Scanning for WiFi Networks

You can also scan for WiFi networks via the Scan() method on the WiFiAdapter and then access the network list via the Networks ObservableCollection property:

protected void ScanForAccessPoints()
{
    Console.WriteLine("Getting list of access points.");
    ObservableCollection<WifiNetwork> networks = Device.WiFiAdapter.Scan();
    if (networks.Count > 0) {
        Console.WriteLine("|-------------------------------------------------------------|---------|");
        Console.WriteLine("|         Network Name             | RSSI |       BSSID       | Channel |");
        Console.WriteLine("|-------------------------------------------------------------|---------|");
        foreach (WifiNetwork accessPoint in networks) {
            Console.WriteLine($"| {accessPoint.Ssid,-32} | {accessPoint.SignalDbStrength,4} | {accessPoint.Bssid,17} |   {accessPoint.ChannelCenterFrequency,3}   |");
        }
    } else {
        Console.WriteLine($"No access points detected.");
    }
}

Performing Requests

Once the network is connected, you can generally use the built-in .NET network methods as usual, however HttpServer is not availble in this beta.

`HttpClient.Request()` Example

The following code illustrates making a request to a web page via the HttpClient class:

using (HttpClient client = new HttpClient()) {
    HttpResponseMessage response = await client.GetAsync(uri);
    response.EnsureSuccessStatusCode();
    string responseBody = await response.Content.ReadAsStringAsync();
    Console.WriteLine(responseBody);
}

Posting

You can also modify the request to POST data. For example, the following code posts a temperature reading to Adafruit.IO:

using (HttpClient client = new HttpClient()) {
    client.DefaultRequestHeaders.Add("X-AIO-Key", [APIO_KEY]);
    client.Timeout = TimeSpan.FromMinutes(10);
    string temperature = "23.70";
    string data = "{\"value\":\"" + temperature + "\"}";
    var content = new StringContent(data, Encoding.UTF8, "application/json");
    var result = client.PostAsync(uri, content).Result;
}

Antenna

Both the Meadow development board and production module have an onboard ceramic chip antenna and a U.FL connector for an external antenna for the 2.4GHz WiFi and Bluetooth radio.

For more information on getting the curent antenna information and switching, see the Antenna guide.

Creating RESTful Web APIs with Maple Server

If you need to expose simple RESTful Web APIs, Meadow.Foundation includes a lightweight web server called Maple Server that may be useful. Check out the Maple Server guide for more information.

These docs are open source. If you find an issue, please file a bug, or send us a pull request. And if you want to contribute, we'd love that too!

Networking