Both the Meadow F7 Feather development board and Core-Compute Module have Wi-Fi networking via the ESP32 co-processor. The Meadow Core-Compute Module also adds optional ethernet capabilities.

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

Connecting to a Wi-Fi Network

To connect to a Wi-Fi network, call the async function Connect, passing in the network name (SSID) and password. It will return a Connection.Status to verify if the connection was successful or if something went wrong, and allowing you to handle those situations.

There are also additional Connect methods that take parameters for cancellation or timeout durations, as well as a reconnect setting.

var wifi = Device.NetworkAdapters.Primary<IWiFiNetworkAdapter>();
var connectionResult = await wifi.Connect("[SSID]", "[PASSWORD]");
if (connectionResult.ConnectionStatus != ConnectionStatus.Success)
{
    throw new Exception($"Cannot connect to network: {connectionResult.ConnectionStatus}");
}
else
{
    Console.WriteLine($"IP Address: {wifi.IpAddress}");
    Console.WriteLine($"Subnet mask: {wifi.SubnetMask}");
    Console.WriteLine($"Gateway: {wifi.Gateway}");
}

Additionally, you can subscribe to the NetworkConnected event thats triggered whenever Meadow has joined the network. You can retrieve the connection properties either from the event arguments or the connected network adapter in this event handler.

var wifi = Device.NetworkAdapters.Primary<IWiFiNetworkAdapter>();
wifi.NetworkConnected += (networkAdapter, networkConnectionEventArgs) =>
{
    Console.WriteLine("Joined network");
    Console.WriteLine($"IP Address: {networkAdapter.IpAddress}.");
    Console.WriteLine($"Subnet mask: {networkAdapter.SubnetMask}");
    Console.WriteLine($"Gateway: {networkAdapter.Gateway}");
};

Scanning for WiFi Networks

You can also scan for WiFi networks via the Scan() method on the IWiFiNetworkAdapter. This method will return a list of the discovered networks.

There are also additional Connect methods that take parameters for cancellation or timeout durations.

async Task ScanForAccessPoints(IWiFiNetworkAdapter wifi)
{
    Console.WriteLine("Getting list of access points.");
    var networks = await wifi.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 available in this release candidate.

Note: SSL validation can sometimes fail due to Meadow’s clock being too far from the current time. This can be resolved by either configuring Meadow to aqcuire the network time at startup, or by setting the clock manually at runtime.

HTTP Get 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);
}

HTTP Post Request Example

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

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 current 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.

Sample projects

You can look through these for usa samples in our Meadow Core Samples repo or refer to these practical projects available on Hackster.

Photo showing a Meadow hooked up to an LCD displaying the date, time, indoor and outdoor temperature and a weather icon.

Weather Station Using Public Web Service Using Meadow
Learn how to connect your Meadow to your local network and get current weather conditions from a free public weather web service.

Video showing a vertical LED matrix showing the current date and then the current time when a button is pressed.

Build a WIFI Connected Clock Using Meadow
Build this nifty clock with Meadow getting the date and time from an NTP server via WIFI and room temperature with an LM35 Analog sensor.

Video showing a Meadow connected to a multi-line character display showing the date, time, indoor and outdoor temperatures, and a weather description.

Make a Meadow indoor/outdoor temperature/weather desk clock
Build this nifty clock for your desk that gives you time and date, along with room and outdoor temperature using a REST service.

 


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!