Assignment 5: Add Wi-Fi scan on ESP32

Now that we have our desktop application showing placeholder or local Wi-Fi list, it’s time to fetch real scan results from the ESP32 device itself.

Objective

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Connect the Slint frontend with a backend task that performs a Wi-Fi scan and updates the UI with real network data.

Step 1: Choose Your WiFi Implementation Path

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Unlike the desktop environment, the embedded environment requires different approaches for WiFi depending on whether you chose no_std or std:

no_std Path (Recommended) ✅

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Crates used:

• esp-hal for hardware abstraction
• esp-wifi for WiFi functionality
• embassy for async runtime (optional)

Benefits:

• Direct hardware control
• Lower memory usage
• Faster boot times
• Predictable behavior

std Path (Alternative)

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Crates used:

• esp-idf-hal for hardware abstraction
• esp-idf-svc for WiFi services
• Standard Rust std library

Use when:

• You need existing ESP-IDF C/C++ components
• You require std-only crates

Step 2: Implement Wi-Fi Scan Task

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no_std Implementation (Recommended)

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A simplified flow using esp-wifi in blocking mode:

use esp_wifi::wifi::WifiController;
use esp_hal::prelude::*;

// Initialize WiFi controller
let mut wifi = WifiController::new(...);

// Perform scan
let networks = wifi.scan().unwrap();

// Process results
for net in networks {
    esp_println::println!("SSID: {:?}, RSSI: {}", net.ssid, net.rssi);
}

std Implementation (Alternative)

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Using ESP-IDF services:

use esp_idf_svc::wifi::{EspWifi, WifiConfiguration};
use esp_idf_hal::peripherals::Peripherals;

// Initialize WiFi service
let peripherals = Peripherals::take().unwrap();
let mut wifi = EspWifi::new(peripherals.modem, ...);

// Perform scan
let scan_result = wifi.scan().unwrap();

// Process results
for ap in scan_result {
    println!("SSID: {:?}, RSSI: {}", ap.ssid, ap.signal_strength);
}

Your code should fetch the list, filter or map it into a simple Rust data structure, and push it to the Slint view model (typically through an FFI bridge, or via slint::SharedVector).

Step 3: Bridge Data to UI

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Use the same WiFiNetwork model and expose it via set_network_list() call or bind it to a SharedVector.

Ensure any updates are done in a safe way (outside ISR) — it’s common to poll or await the scan completion and then call UI updates from main or spawned tasks.

Step 4: Flash and Verify

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Navigate to your board’s directory and flash the updated application:

no_std Path (Recommended)

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# For M5Stack CoreS3
cd slint-esp-workshop/esp32/no_std/m5stack-cores3
cargo run --release

# For ESoPe Board
cd slint-esp-workshop/esp32/no_std/esope-sld-c-w-s3
cargo run --release

# For ESP32-S3-BOX-3
cd slint-esp-workshop/esp32/no_std/esp32-s3-box-3
cargo run --release

std Path (Alternative)

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# For M5Stack CoreS3
cd slint-esp-workshop/esp32/std/m5stack-cores3
cargo run --release

# For ESP32-S3-BOX-3
cd slint-esp-workshop/esp32/std/esp32-s3-box-3
cargo run --release

Bootloader Mode (if needed)

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For ESoPe board users:

• Connect ESP-Prog
• Hold BOOT, press RESET, then release BOOT

For M5Stack CoreS3 and other boards:

• Usually enters bootloader mode automatically
• If issues occur, press and hold BOOT, then press RESET

After flashing, check the logs and verify that real networks are displayed in the UI.

Notes

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• You may need to allocate enough memory for scan results
• Use heapless or alloc containers for passing data into Slint view models
• Ensure Wi-Fi driver is initialized before scanning

Extra Credit

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• Add a button to trigger a new scan
• Highlight the strongest signal
• Sort by RSSI