Code shared from the Rust Playground

playground.rs

#![no_std]
#![no_main]

use defmt::info;
use embassy_executor::Spawner;
use embassy_stm32::{
    bind_interrupts, peripherals,
    time::Hertz,
    usb_otg::{self, Driver, Instance},
    Config,
};
use embassy_usb::{
    class::cdc_acm::{CdcAcmClass, State},
    driver::EndpointError,
    Builder,
};
use futures::future::join;
use {defmt_rtt as _, panic_probe as _};

bind_interrupts!(struct Irqs {
    OTG_HS => usb_otg::InterruptHandler<peripherals::USB_OTG_HS>;
});

#[embassy_executor::main]
async fn main(_spawner: Spawner) {
    info!("Hello World!");

    let mut config = Config::default();
    {
        use embassy_stm32::rcc::*;
        config.rcc.hse = Some(Hse {
            freq: Hertz(8_000_000),
            mode: HseMode::Oscillator,
        });
        config.rcc.pll_src = PllSource::HSE;
        config.rcc.pll = Some(Pll {
            prediv: PllPreDiv::DIV4,
            mul: PllMul::MUL168,
            divp: Some(PllPDiv::DIV2), // 8mhz / 4 * 168 / 2 = 168Mhz.
            divq: Some(PllQDiv::DIV7), // 8mhz / 4 * 168 / 7 = 48Mhz.
            divr: None,
        });
        config.rcc.ahb_pre = AHBPrescaler::DIV1;
        config.rcc.apb1_pre = APBPrescaler::DIV4;
        config.rcc.apb2_pre = APBPrescaler::DIV2;
        config.rcc.sys = Sysclk::PLL1_P;
        // config.rcc.mux.clk48sel = mux::Clk48sel::PLL1_Q;
    }
    let p = embassy_stm32::init(config);

    // Create the driver, from the HAL.
    let mut ep_out_buffer = [0u8; 256];
    let mut config = embassy_stm32::usb_otg::Config::default();
    config.vbus_detection = true;
    let driver = Driver::new_fs(
        p.USB_OTG_HS,
        Irqs,
        p.PB15,
        p.PB14,
        &mut ep_out_buffer,
        config,
    );

    // Create embassy-usb Config
    let mut config = embassy_usb::Config::new(0xc0de, 0xcafe);
    config.manufacturer = Some("Embassy");
    config.product = Some("USB-serial example");
    config.serial_number = Some("12345678");

    // Required for windows compatibility.
    // https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.9.1/kconfig/CONFIG_CDC_ACM_IAD.html#help
    config.device_class = 0xEF;
    config.device_sub_class = 0x02;
    config.device_protocol = 0x01;
    config.composite_with_iads = true;

    // Create embassy-usb DeviceBuilder using the driver and config.
    // It needs some buffers for building the descriptors.
    let mut device_descriptor = [0; 256];
    let mut config_descriptor = [0; 256];
    let mut bos_descriptor = [0; 256];
    // let mut msos_descriptor = [0; 256];
    let mut control_buf = [0; 64];

    let mut state = State::new();

    let mut builder = Builder::new(
        driver,
        config,
        &mut device_descriptor,
        &mut config_descriptor,
        &mut bos_descriptor,
        // &mut msos_descriptor,
        &mut [], // no msos descriptors
        &mut control_buf,
    );

    // Create classes on the builder.
    let mut class = CdcAcmClass::new(&mut builder, &mut state, 64);

    // Build the builder.
    let mut usb = builder.build();

    // Run the USB device.
    let usb_fut = usb.run();

    // Do stuff with the class!
    let echo_fut = async {
        loop {
            class.wait_connection().await;
            info!("Connected");
            let _ = echo(&mut class).await;
            info!("Disconnected");
        }
    };

    // Run everything concurrently.
    // If we had made everything `'static` above instead, we could do this using separate tasks instead.
    join(usb_fut, echo_fut).await;
}

struct Disconnected {}

impl From<EndpointError> for Disconnected {
    fn from(val: EndpointError) -> Self {
        match val {
            EndpointError::BufferOverflow => panic!("Buffer overflow"),
            EndpointError::Disabled => Disconnected {},
        }
    }
}

async fn echo<'d, T: Instance + 'd>(
    class: &mut CdcAcmClass<'d, Driver<'d, T>>,
) -> Result<(), Disconnected> {
    let mut buf = [0; 64];
    loop {
        let n = class.read_packet(&mut buf).await?;
        let data = &buf[..n];
        info!("data: {:x}", data);
        class.write_packet(data).await?;
    }
}