贴个usb的例子，如果用寄存器要写死人吧？

//! CDC-ACM serial port example using interrupts.
//! Target board: Blue Pill
#![no_std]
#![no_main]

extern crate panic_semihosting;

use cortex_m::asm::{delay, wfi};
use cortex_m_rt::entry;
use embedded_hal::digital::v2::OutputPin;
use stm32f1xx_hal::pac::{interrupt, Interrupt};
use stm32f1xx_hal::usb::{Peripheral, UsbBus, UsbBusType};
use stm32f1xx_hal::{prelude::*, stm32};
use usb_device::{bus::UsbBusAllocator, prelude::*};
use usbd_serial::{SerialPort, USB_CLASS_CDC};

static mut USB_BUS: Option<UsbBusAllocator<UsbBusType>> = None;
static mut USB_SERIAL: Option<usbd_serial::SerialPort<UsbBusType>> = None;
static mut USB_DEVICE: Option<UsbDevice<UsbBusType>> = None;

#[entry]
fn main() -> ! {
    let p = cortex_m::Peripherals::take().unwrap();
    let dp = pac::Peripherals::take().unwrap();

    let mut flash = dp.FLASH.constrain();
    let mut rcc = dp.RCC.constrain();

    let clocks = rcc
        .cfgr
        .use_hse(8.mhz())
        .sysclk(48.mhz())
        .pclk1(24.mhz())
        .freeze(&mut flash.acr);

    assert!(clocks.usbclk_valid());

    let mut gpioa = dp.GPIOA.split(&mut rcc.apb2);

    // BluePill board has a pull-up resistor on the D+ line.
    // Pull the D+ pin down to send a RESET condition to the USB bus.
    // This forced reset is needed only for development, without it host
    // will not reset your device when you upload new firmware.
    let mut usb_dp = gpioa.pa12.into_push_pull_output(&mut gpioa.crh);
    usb_dp.set_low();
    delay(clocks.sysclk().0 / 100);

    let usb_dm = gpioa.pa11;
    let usb_dp = usb_dp.into_floating_input(&mut gpioa.crh);

    let usb = Peripheral {
        usb: dp.USB,
        pin_dm: usb_dm,
        pin_dp: usb_dp,
    };

    // Unsafe to allow access to static variables
    unsafe {
        let bus = UsbBus::new(usb);

        USB_BUS = Some(bus);

        USB_SERIAL = Some(SerialPort::new(USB_BUS.as_ref().unwrap()));

        let usb_dev = UsbDeviceBuilder::new(USB_BUS.as_ref().unwrap(), UsbVidPid(0x16c0, 0x27dd))
            .manufacturer("Fake company")
            .product("Serial port")
            .serial_number("TEST")
            .device_class(USB_CLASS_CDC)
            .build();

        USB_DEVICE = Some(usb_dev);
    }

    let mut nvic = p.NVIC;

    nvic.enable(Interrupt::USB_HP_CAN_TX);
    nvic.enable(Interrupt::USB_LP_CAN_RX0);

    loop {
        wfi();
    }
}

#[interrupt]
fn USB_HP_CAN_TX() {
    usb_interrupt();
}

#[interrupt]
fn USB_LP_CAN_RX0() {
    usb_interrupt();
}

fn usb_interrupt() {
    let usb_dev = unsafe { USB_DEVICE.as_mut().unwrap() };
    let serial = unsafe { USB_SERIAL.as_mut().unwrap() };

    if !usb_dev.poll(&mut [serial]) {
        return;
    }

    let mut buf = [0u8; 8];

    match serial.read(&mut buf) {
        Ok(count) if count > 0 => {
            // Echo back in upper case
            for c in buf[0..count].iter_mut() {
                if 0x61 <= *c && *c <= 0x7a {
                    *c &= !0x20;
                }
            }

            serial.write(&buf[0..count]).ok();
        }
        _ => {}
    }
}
【 在 dismoon (伐开心要包包) 的大作中提到: 】
: 所以为啥你非要用HAL，寄存器操作不香么
--
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