BLE Module

Let's start by creating the ble module.

ble/mod.rs file

Here, we define a simple function. It calls softdevice_config (which we will define shortly in config.rs) to get the SoftDevice configuration. Then we enable the SoftDevice using that config.

#![allow(unused)]
fn main() {
pub mod adv;
pub mod config;

use crate::ble::config::softdevice_config;

use {defmt_rtt as _, panic_probe as _};

use nrf_softdevice::Softdevice;

pub fn get_soft_device() -> &'static mut Softdevice {
    let sd_config = softdevice_config();
    Softdevice::enable(&sd_config)
}

}

This gives us an instance of the Softdevice struct. We will call get_soft_device() from the main function later and do further actions on the instance.

ble/adv.rs file

Next, we will create a module to prepare the advertisement data. We already covered the core ideas behind advertising in the GAP section.

We use LegacyAdvertisementBuilder to prepare the advertisement payload. Here, we set the flags to make our device discoverable. For example, we use GeneralDiscovery to keep advertising until connected, and LE_Only to say we don’t support Bluetooth Classic.

We also add the 16-bit UUID for the BATTERY service to let central devices know what we support. The DEVICE_NAME is the constnat ("implRust") that we will define later in the config.rs file.

#![allow(unused)]
fn main() {
use crate::ble::config::DEVICE_NAME;

use {defmt_rtt as _, panic_probe as _};

use nrf_softdevice::ble::{
    advertisement_builder::{
        Flag, LegacyAdvertisementBuilder, LegacyAdvertisementPayload, ServiceList, ServiceUuid16,
    },
    peripheral,
};

static ADV_DATA: LegacyAdvertisementPayload = LegacyAdvertisementBuilder::new()
    .flags(&[Flag::GeneralDiscovery, Flag::LE_Only])
    .services_16(ServiceList::Complete, &[ServiceUuid16::BATTERY])
    .full_name(DEVICE_NAME)
    .build();

static SCAN_DATA: [u8; 0] = []; 

pub fn get_adv() -> peripheral::ConnectableAdvertisement<'static> {
    peripheral::ConnectableAdvertisement::ScannableUndirected {
        adv_data: &ADV_DATA,
        scan_data: &SCAN_DATA,
    }
}
}

At the end, we return a ScannableUndirected advertisement type using peripheral::ConnectableAdvertisement. It means our device:

• advertises to any nearby central (not targeting a specific one)
• accepts connection requests
• responds to scan requests with extra info