Module teensy4_bsp::usb[−][src]

This is supported on crate feature usb-logging only.

Expand description

Teensy 4 USB, taken from the original Teensy 4 C libraries

The USB stack provides a log implementation for logging over USB. It also provides a simpler Reader and Writer for performing I/O over the CDC interface. Use the macros of the log crate to write data over USB. Or, acquire a raw Reader and Writer to perform your own USB I/O.

You’re responsible for driving the USB driver with repeated calls to poll. See the poll documentation for considerations on where to call poll.

Most initialization functions require the imxrt_ral’s USB1 instance. You can acquire the instance through the HAL, which is exported by the BSP:

use teensy4_bsp as bsp;
use bsp::hal::ral::usb::USB1;

let instance = USB1::take().unwrap();

Logging Example

This example drives the USB logging system through the USB ISR.

use teensy4_bsp as bsp;
use bsp::hal::ral::usb::USB1;
use bsp::interrupt;

use cortex_m::interrupt::Mutex;
use core::cell::RefCell;

static POLLER: Mutex<RefCell<Option<bsp::usb::Poller>>> = Mutex::new(RefCell::new(None));

// Enable this macro for your real system!
// #[cortex_m_rt::interrupt]
fn USB_OTG1() {
    cortex_m::interrupt::free(|cs| {
        POLLER
            .borrow(cs)
            .borrow_mut()
            .as_mut()
            .map(|poller| poller.poll());
    });
}

let (poller, _) = bsp::usb::init(
    USB1::take().unwrap(),
    bsp::usb::LoggingConfig {
        filters: &[("motor", None)],
        ..Default::default()
    },
)
.unwrap();

cortex_m::interrupt::free(|cs| {
    *POLLER.borrow(cs).borrow_mut() = Some(poller);
    // Safety: invoked in a critical section that also prepares the ISR
    // shared memory. ISR memory is ready by the time the ISR runs.
    unsafe { cortex_m::peripheral::NVIC::unmask(bsp::interrupt::USB_OTG1) };
});

// You can now begin logging.
log::info!("Hello world! 3 + 2 = {}", 5);

Reader / Writer Example

This example will manually call poll in an idle loop to drive USB I/O.

use teensy4_bsp as bsp;
use bsp::hal::ral::usb::USB1;
use core::fmt::Write;

let (mut poller, mut reader, mut writer) = bsp::usb::split(USB1::take().unwrap()).unwrap();

write!(writer, "Hello world! 3 + 2 = {}", 5).unwrap();

'idle: loop {
    // Other work...

    let status = poller.poll();
    if status.cdc_rx_complete() {
        // Read the data
        let mut buffer: [u8; 256] = [0; 256];
        reader.read(&mut buffer).unwrap();
    }
}