Setting Up the Project

The project template we have been using so far is intended for general Raspberry Pi Pico development. Since networking on the Pico W requires additional setup, we will use a different project template for this tutorial.

The template already includes support for the CYW43439 wireless chip, the required firmware files, and the project configuration needed for networking.

Create a new project with:

cargo generate --git https://github.com/ImplFerris/pico-w-template.git --tag v0.1.1

Alternatively, you can clone the template and generate the project from your local copy:

git clone https://github.com/ImplFerris/pico-w-template.git

# Replace /path/to/ with the directory where you cloned the repository.
cargo generate /path/to/pico-w-template --tag v0.1.1

When prompted, enter a project name as usual and enable the defmt option. Throughout this tutorial, we will use defmt for logging, so you will need the Raspberry Pi Debug Probe. If you do not have one, you can disable the defmt option and use USB serial logging approach instead.

Project Structure

In the template, I have moved the Wi-Fi initialization code into a separate wifi module because it is boilerplate code. This keeps main.rs small and allows us to focus on the application logic.

.
├── build.rs
├── Cargo.toml
├── Embed.toml
├── firmware
│   ├── 43439A0.bin
│   ├── 43439A0_clm.bin
│   └── nvram_rp2040.bin
├── memory.x
├── src
│   ├── main.rs
│   └── wifi.rs

You will also notice an additional firmware file named nvram_rp2040.bin. Recent versions of the cyw43 crate require this file when initializing the CYW43439 wireless chip.

I recommend taking a few minutes to browse through main.rs and wifi.rs to get familiar with the project structure. In the following sections, we will go through the code in detail.

Wi-Fi Credentials

I configured the template to read the Wi-Fi network name (SSID) and password from environment variables at compile time.

#![allow(unused)]
fn main() {
const WIFI_NETWORK: &str = env!("SSID");
const WIFI_PASSWORD: &str = env!("PASSWORD");
}

Whenever you build or flash the program, make sure to provide these environment variables. Alternatively, you can export them in your shell before running Cargo.

SSID=YOUR_WIFI PASSWORD=YOUR_WIFI_PASSWORD cargo build --release
# for flashing
# SSID=YOUR_WIFI PASSWORD=YOUR_WIFI_PASSWORD cargo embed --release

The Main

Before we send our first HTTP request, let’s first look at the current main.rs.

At this point, the program contains only the boilerplate required to initialize the CYW43 driver, create the networking stack, connect to a Wi-Fi network, and wait until the network is ready. We have not added any HTTP client code yet.

#[embassy_executor::main]
async fn main(spawner: Spawner) {
    let p = embassy_rp::init(Default::default());

    info!("Initializing the program");

    let (net_device, mut control) = wifi::init_cyw43(
        spawner, p.PIO0, p.DMA_CH0, p.PIN_23, p.PIN_24, p.PIN_25, p.PIN_29,
    )
    .await;

    let mut rng = RoscRng;
    let seed = rng.next_u64();

    let stack = wifi::init_net_stack(spawner, net_device, seed);

    wifi::join_wifi(&mut control, WIFI_NETWORK, WIFI_PASSWORD).await;
    wifi::bring_up_stack(stack).await;
    info!("Stack is up!");

    loop {
        Timer::after_secs(1).await;
    }
}

In the next chapter, we will look at how the wifi module works.