main.rs

#![no_std]
#![no_main]

use panic_halt as _;
use stm32f1xx_hal::{pac, prelude::*, rcc, usb};

use usb_device::prelude::*;
use usbd_serial::{SerialPort, USB_CLASS_CDC};

#[cortex_m_rt::entry]
fn main() -> ! {
    rtt_target::rtt_init_print!();

    let cp = cortex_m::Peripherals::take().unwrap();
    let dp = pac::Peripherals::take().unwrap();

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

    let cfgr = rcc.cfgr.use_hse(16.MHz()).sysclk(48.MHz()).pclk1(24.MHz());

    let clockconf = rcc::Config::from_cfgr(cfgr);
    rtt_target::rprintln!("config: {:?}", clockconf);

    let clocks = rcc::CFGR::default().freeze_with_config(clockconf, &mut flash.acr);

    rtt_target::rprintln!("clocks: {:?}", clocks);
    rtt_target::rprintln!("usb clock valid: {:?}", clocks.usbclk_valid());

    let mut delay = cp.SYST.delay(&clocks);

    let mut gpioc = dp.GPIOC.split();

    let mut led = gpioc.pc13.into_push_pull_output(&mut gpioc.crh);
    led.set_high(); // off

    // pull d+ down to reset USB bus, so it re-enumerates after upload
    let mut gpioa = dp.GPIOA.split();
    let mut usb_dp = gpioa.pa12.into_push_pull_output(&mut gpioa.crh);
    usb_dp.set_low();
    delay.delay_ms(10u8);

    let usb = usb::Peripheral {
        usb: dp.USB,
        pin_dm: gpioa.pa11,
        pin_dp: usb_dp.into_floating_input(&mut gpioa.crh),
    };
    let usb_bus = usb::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_low(); // on

                // Echo back upper case
                for c in buf[..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_high(); // off
    }
}