nRF-Modem

This is a library that provides a high-level async API for the nRF9160 modem.

It can be used with any executor.

Setup

There are a couple of things you must do to be able to use the library.

First of which, make sure to have the llvm-tools installed. This can be done using rustup component add llvm-tools-preview.

The library also needs some libc functions. The best way to import them is with tinyrlibc. As of writing the newest release is 0.3.0. This version does not include a needed API, so it's better to include the latest master branch or any newer released version.

Nonsecure

Nordic has made it so that the modem can only be used when in the nonsecure context. Make sure you are in that context by using e.g. the SPM.

Interrupts

The EGU1 and IPC interrupts must be routed to the modem software. In embassy you can do that as follows:

let egu1 = embassy_nrf::interrupt::take!(EGU1);
egu1.set_priority(Priority::P4);
egu1.set_handler(|_| {
    nrf_modem::application_irq_handler();
    cortex_m::asm::sev();
});
egu1.enable();

let ipc = embassy_nrf::interrupt::take!(IPC);
ipc.set_priority(Priority::P0);
ipc.set_handler(|_| {
    nrf_modem::ipc_irq_handler();
    cortex_m::asm::sev();
});
ipc.enable();

This can be done using the normal cortex-m-rt interrupts as well of course.

Power

The DC/DC converter is automatically enabled for you when the library is initialized. This is required for certified operation of the modem.

Initialization

Now it's time to initialize the library. Here you can make a selection for the connectivity for the modem:

nrf_modem::init(SystemMode {
    lte_support: true,
    lte_psm_support: true,
    nbiot_support: true,
    gnss_support: true,
    preference: ConnectionPreference::None,
})
.await
.unwrap();

Now the library is ready to be used.

AT Commands

let response = nrf_modem::send_at::<64>("AT+CGMI").await.unwrap();
assert_eq!(response, "AT+CGMI\n\rNordic Semiconductor ASA\n\rOK\n\r");

DNS request

let google_ip = nrf_modem::get_host_by_name("www.google.com").await.unwrap();

Tcp connection

let stream = nrf_modem::TcpStream::connect(SocketAddr::from((google_ip, 80))).await.unwrap();

stream
    .write("GET / HTTP/1.0\nHost: google.com\r\n\r\n".as_bytes())
    .await
    .unwrap();

let mut buffer = [0; 1024];
let received = stream.receive(&mut buffer).await.unwrap();

println!("Google response: {}", core::str::from_utf8(received).unwrap());

// Drop the stream async (normal Drop is ok too, but that's blocking)
stream.deactivate().await.unwrap();

Udp socket

let socket =
    nrf_modem::UdpSocket::bind(SocketAddr::from_str("0.0.0.0:53").unwrap())
        .await
        .unwrap();

// Do a DNS request
socket
    .send_to(
        &[
            0xdb, 0x42, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x77,
            0x77, 0x77, 0x0C, 0x6E, 0x6F, 0x72, 0x74, 0x68, 0x65, 0x61, 0x73, 0x74, 0x65, 0x72,
            0x6E, 0x03, 0x65, 0x64, 0x75, 0x00, 0x00, 0x01, 0x00, 0x01,
        ],
        SocketAddr::from_str("8.8.8.8:53").unwrap(),
    )
    .await
    .unwrap();
let (response, source_addr) = socket.receive_from(&mut buffer).await.unwrap();

println!("Result: {:X}", response);
println!("Source: {}", source_addr);

dragonnn / nrf-modem