usb_serial.rs

//! CDC-ACM serial port example using polling in a busy loop.
//! Target board: Blue Pill
//!
//! Note:
//! When building this since this is a larger program,
//! one would need to build it using release profile
//! since debug profiles generates artifacts that
//! cause FLASH overflow errors due to their size
#![no_std]
#![no_main]

extern crate panic_semihosting;

use cortex_m::asm::delay;
use cortex_m_rt::entry;
use stm32f1xx_hal::usb::{Peripheral, UsbBus};
use stm32f1xx_hal::{pac, prelude::*};
use usb_device::prelude::*;
use usbd_serial::{SerialPort, USB_CLASS_CDC};

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

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

    // Configure the on-board LED (PC13, green)
    let mut gpioc = dp.GPIOC.split();
    let mut led = gpioc.pc13.into_push_pull_output(&mut gpioc.crh);
    led.set_high(); // Turn off

    let mut gpioa = dp.GPIOA.split();

    // 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().raw() / 100);

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

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

    let mut usb_dev = UsbDeviceBuilder::new(&usb_bus, UsbVidPid(0x16c0, 0x27dd))
        .device_class(USB_CLASS_CDC)
        .strings(&[StringDescriptors::default()
            .manufacturer("Fake Company")
            .product("Serial port")
            .serial_number("TEST")])
        .unwrap()
        .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(); // 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_high(); // Turn off
    }
}