Add USB example

Cargo.toml

@@ -41,6 +41,8 @@ stm32-usbd = { version = "0.5.0", features = ["ram_access_2x16"], optional = tru
 
 [dev-dependencies]
 panic-halt = "0.2"
+usb-device = "0.2.3"
+usbd-serial = "0.1.0"
 
 [features]
 device-selected = []
@@ -81,3 +83,7 @@ required-features = ["stm32f042", "rt"]
 [[example]]
 name = "dac"
 required-features = ["stm32f072"]
+
+[[example]]
+name = "usb_serial"
+required-features = ["rt", "stm32f042", "stm32-usbd"]

examples/usb_serial.rs

@@ -0,0 +1,90 @@
+//! CDC-ACM serial port example using polling in a busy loop.
+//! Target board: NUCLEO-F042K6
+#![no_std]
+#![no_main]
+
+extern crate panic_halt;
+
+use cortex_m_rt::entry;
+use stm32f0xx_hal::usb::{Peripheral, UsbBus};
+use stm32f0xx_hal::{prelude::*, stm32};
+use usb_device::prelude::*;
+use usbd_serial::{SerialPort, USB_CLASS_CDC};
+
+#[entry]
+fn main() -> ! {
+    let mut dp = stm32::Peripherals::take().unwrap();
+
+    /* Uncomment the following lines if you have a chip in TSSOP20 (STM32F042F)
+       or UFQFPN28 (STM32F042G) package
+       This code enables clock for SYSCFG and remaps USB pins to PA9 and PA10.
+    */
+    //dp.RCC.apb2enr.modify(|_, w| w.syscfgen().set_bit());
+    //dp.SYSCFG.cfgr1.modify(|_, w| w.pa11_pa12_rmp().remapped());
+
+    let mut rcc = dp
+        .RCC
+        .configure()
+        .hsi48()
+        .enable_crs(dp.CRS)
+        .sysclk(48.mhz())
+        .pclk(24.mhz())
+        .freeze(&mut dp.FLASH);
+
+    // Configure the on-board LED (LD3, green)
+    let gpiob = dp.GPIOB.split(&mut rcc);
+    let mut led = cortex_m::interrupt::free(|cs| gpiob.pb3.into_push_pull_output(cs));
+    led.set_low(); // Turn off
+
+    let gpioa = dp.GPIOA.split(&mut rcc);
+
+    let usb = Peripheral {
+        usb: dp.USB,
+        pin_dm: gpioa.pa11,
+        pin_dp: gpioa.pa12,
+    };
+    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
+    }
+}