usb_serial.rs

//! CDC-ACM serial port example using polling in a busy loop.
//! Target board: NUCLEO-L432KC
#![no_std]
#![no_main]

extern crate panic_semihosting;

use cortex_m_rt::entry;
use stm32l4xx_hal::usb::{Peripheral, UsbBus};
use stm32l4xx_hal::{prelude::*, stm32};
use usb_device::prelude::*;
use usbd_serial::{SerialPort, USB_CLASS_CDC};

fn enable_crs() {
    let rcc = unsafe { &(*stm32::RCC::ptr()) };
    rcc.apb1enr1.modify(|_, w| w.crsen().set_bit());
    let crs = unsafe { &(*stm32::CRS::ptr()) };
    // Initialize clock recovery
    // Set autotrim enabled.
    crs.cr.modify(|_, w| w.autotrimen().set_bit());
    // Enable CR
    crs.cr.modify(|_, w| w.cen().set_bit());
}

/// Enables VddUSB power supply
fn enable_usb_pwr() {
    // Enable PWR peripheral
    let rcc = unsafe { &(*stm32::RCC::ptr()) };
    rcc.apb1enr1.modify(|_, w| w.pwren().set_bit());

    // Enable VddUSB
    let pwr = unsafe { &*stm32::PWR::ptr() };
    pwr.cr2.modify(|_, w| w.usv().set_bit());
}

#[entry]
fn main() -> ! {
    let dp = stm32::Peripherals::take().unwrap();

    let mut flash = dp.FLASH.constrain();
    let mut rcc = dp.RCC.constrain();
    let mut pwr = dp.PWR.constrain(&mut rcc.apb1r1);

    let _clocks = rcc
        .cfgr
        .hsi48(true)
        .sysclk(80.MHz())
        .freeze(&mut flash.acr, &mut pwr);

    enable_crs();

    // disable Vddusb power isolation
    enable_usb_pwr();

    // Configure the on-board LED (LD3, green)
    let mut gpiob = dp.GPIOB.split(&mut rcc.ahb2);
    let mut led = gpiob
        .pb3
        .into_push_pull_output(&mut gpiob.moder, &mut gpiob.otyper);
    led.set_low(); // Turn off

    let mut gpioa = dp.GPIOA.split(&mut rcc.ahb2);

    let usb = Peripheral {
        usb: dp.USB,
        pin_dm: gpioa
            .pa11
            .into_alternate(&mut gpioa.moder, &mut gpioa.otyper, &mut gpioa.afrh),
        pin_dp: gpioa
            .pa12
            .into_alternate(&mut gpioa.moder, &mut gpioa.otyper, &mut gpioa.afrh),
    };
    let usb_bus = UsbBus::new(usb);

    let mut serial = SerialPort::new(&usb_bus);

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

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

        let mut buf = [0u8; 64];

        match serial.read(&mut buf) {
            Ok(count) if count > 0 => {
                led.set_high(); // Turn on

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

                let mut write_offset = 0;
                while write_offset < count {
                    match serial.write(&buf[write_offset..count]) {
                        Ok(len) if len > 0 => {
                            write_offset += len;
                        }
                        _ => {}
                    }
                }
            }
            _ => {}
        }

        led.set_low(); // Turn off
    }
}