#![cfg_attr(docsrs, procmacros::doc_replace)]
//! USB Serial/JTAG Controller (USB_SERIAL_JTAG)
//!
//! ## Overview
//!
//! The USB Serial/JTAG controller can be used to program the SoC's flash, read
//! program output, or attach a debugger to the running program. This is
//! possible for any computer with a USB host (hereafter referred to as 'host'),
//! without any active external components.
//!
//! This peripheral integrates the functionality of both a USB-to-serial
//! converter as well as a USB-to-JTAG adapter. As this device directly
//! interfaces with an external USB host using only the two data lines required
//! by USB 2.0, only two pins are required to be dedicated to this functionality
//! for debugging.
//!
//! The USB Serial/JTAG controller boasts the following features:
//!
//! - Hardwired for CDC-ACM (Communication Device Class - Abstract Control Model) and JTAG adapter
//!   functionality
//! - Integrates CDC-ACM adherent serial port emulation (plug-and-play on most modern OSes);
//!   supports host controllable chip reset and entry into download mode
//! - Allows fast communication with CPU debugging core using a compact representation of JTAG
//!   instructions
//! - Two OUT Endpoints and three IN Endpoints in addition to Control Endpoint 0; Up to 64-byte data
//!   payload size
//! - Internal PHY means that very few or no external components needed to connect to a host
//!   computer
//!
//! ## Usage
//!
//! The USB Serial/JTAG driver implements a number of third-party traits, with
//! the intention of making the HAL inter-compatible with various device drivers
//! from the community. This includes, but is not limited to, the [embedded-hal]
//! and [embedded-io] blocking traits, and the [embedded-hal-async]
//! and [embedded-io-async] asynchronous traits.
//!
//! In addition to the interfaces provided by these traits, native APIs are also
//! available. See the examples below for more information on how to interact
//! with this driver.
//!
//! ## Examples
//!
//! ### Sending and Receiving Data
//! ```rust, no_run
//! # {before_snippet}
//! use esp_hal::usb_serial_jtag::UsbSerialJtag;
//!
//! let mut usb_serial = UsbSerialJtag::new(peripherals.USB_DEVICE);
//!
//! // Write bytes out over the USB Serial/JTAG:
//! usb_serial.write(b"Hello, world!")?;
//! # {after_snippet}
//! ```
//!
//! ### Splitting the USB Serial/JTAG into TX and RX Components
//! ```rust, no_run
//! # {before_snippet}
//! use esp_hal::usb_serial_jtag::UsbSerialJtag;
//!
//! let mut usb_serial = UsbSerialJtag::new(peripherals.USB_DEVICE);
//! // The USB Serial/JTAG can be split into separate Transmit and Receive
//! // components:
//! let (mut rx, mut tx) = usb_serial.split();
//!
//! // Each component can be used individually to interact with the USB
//! // Serial/JTAG:
//! tx.write(&[42u8])?;
//! let byte = rx.read_byte()?;
//! # {after_snippet}
//! ```
//!
//! ### How to output text using USB Serial/JTAG.
//! ```rust, no_run
//! # {before_snippet}
//! # use esp_hal::{delay::Delay, usb_serial_jtag::UsbSerialJtag, Blocking};
//!
//! let delay = Delay::new();
//!
//! let mut usb_serial = UsbSerialJtag::new(peripherals.USB_DEVICE);
//! usb_serial.set_interrupt_handler(usb_device);
//! usb_serial.listen_rx_packet_recv_interrupt();
//!
//! critical_section::with(|cs| USB_SERIAL.borrow_ref_mut(cs).replace(usb_serial));
//!
//! loop {
//!     println!("Send keystrokes to see the interrupt trigger");
//!     delay.delay(Duration::from_secs(1));
//! }
//! # }
//!
//! # use critical_section::Mutex;
//! # use core::{cell::RefCell, fmt::Write};
//! # use esp_hal::usb_serial_jtag::UsbSerialJtag;
//! static USB_SERIAL: Mutex<RefCell<Option<UsbSerialJtag<'static, esp_hal::Blocking>>>> =
//!     Mutex::new(RefCell::new(None));
//!
//! #[esp_hal::handler]
//! fn usb_device() {
//!     critical_section::with(|cs| {
//!         let mut usb_serial = USB_SERIAL.borrow_ref_mut(cs);
//!         if let Some(usb_serial) = usb_serial.as_mut() {
//!             println!("USB serial interrupt");
//!
//!             while let nb::Result::Ok(c) = usb_serial.read_byte() {
//!                 println!("Read byte: {:02x}", c);
//!             }
//!
//!             usb_serial.reset_rx_packet_recv_interrupt();
//!         }
//!     });
//! }
//! ```
//!
//! [embedded-hal]: https://docs.rs/embedded-hal/latest/embedded_hal/
//! [embedded-io]: https://docs.rs/embedded-io/latest/embedded_io/
//! [embedded-hal-async]: https://docs.rs/embedded-hal-async/latest/embedded_hal_async/
//! [embedded-io-async]: https://docs.rs/embedded-io-async/latest/embedded_io_async/

#[instability::unstable]
use core::task::Poll;
use core::{convert::Infallible, marker::PhantomData};

use procmacros::handler;

use crate::{
    Async,
    Blocking,
    DriverMode,
    asynch::AtomicWaker,
    pac::usb_device::RegisterBlock,
    peripherals::USB_DEVICE,
    system::{Peripheral, PeripheralClockControl},
};

/// Custom USB serial error type
type Error = Infallible;

/// USB Serial/JTAG (Full-duplex)
pub struct UsbSerialJtag<'d, Dm: DriverMode> {
    rx: UsbSerialJtagRx<'d, Dm>,
    tx: UsbSerialJtagTx<'d, Dm>,
}

/// USB Serial/JTAG (Transmit)
pub struct UsbSerialJtagTx<'d, Dm: DriverMode> {
    peripheral: USB_DEVICE<'d>,
    phantom: PhantomData<Dm>,
}

/// USB Serial/JTAG (Receive)
pub struct UsbSerialJtagRx<'d, Dm: DriverMode> {
    peripheral: USB_DEVICE<'d>,
    phantom: PhantomData<Dm>,
}

impl<'d, Dm> UsbSerialJtagTx<'d, Dm>
where
    Dm: DriverMode,
{
    fn new_inner(peripheral: USB_DEVICE<'d>) -> Self {
        Self {
            peripheral,
            phantom: PhantomData,
        }
    }

    fn regs(&self) -> &RegisterBlock {
        self.peripheral.register_block()
    }

    /// Write data to the serial output in chunks of up to 64 bytes
    pub fn write(&mut self, data: &[u8]) -> Result<(), Error> {
        for chunk in data.chunks(64) {
            for byte in chunk {
                self.regs()
                    .ep1()
                    .write(|w| unsafe { w.rdwr_byte().bits(*byte) });
            }
            self.regs().ep1_conf().modify(|_, w| w.wr_done().set_bit());

            // FIXME: raw register access
            while self.regs().ep1_conf().read().bits() & 0b011 == 0b000 {
                // wait
            }
        }

        Ok(())
    }

    /// Write data to the serial output in a non-blocking manner
    /// Requires manual flushing (automatically flushed every 64 bytes)
    pub fn write_byte_nb(&mut self, word: u8) -> nb::Result<(), Error> {
        if self
            .regs()
            .ep1_conf()
            .read()
            .serial_in_ep_data_free()
            .bit_is_set()
        {
            // the FIFO is not full
            unsafe { self.regs().ep1().write(|w| w.rdwr_byte().bits(word)) };

            Ok(())
        } else {
            Err(nb::Error::WouldBlock)
        }
    }

    /// Flush the output FIFO and block until it has been sent
    pub fn flush_tx(&mut self) -> Result<(), Error> {
        self.regs().ep1_conf().modify(|_, w| w.wr_done().set_bit());

        // FIXME: raw register access
        while self.regs().ep1_conf().read().bits() & 0b011 == 0b000 {
            // wait
        }

        Ok(())
    }

    /// Flush the output FIFO but don't block if it isn't ready immediately
    pub fn flush_tx_nb(&mut self) -> nb::Result<(), Error> {
        self.regs().ep1_conf().modify(|_, w| w.wr_done().set_bit());

        // FIXME: raw register access
        if self.regs().ep1_conf().read().bits() & 0b011 == 0b000 {
            Err(nb::Error::WouldBlock)
        } else {
            Ok(())
        }
    }
}

impl<'d, Dm> UsbSerialJtagRx<'d, Dm>
where
    Dm: DriverMode,
{
    fn new_inner(peripheral: USB_DEVICE<'d>) -> Self {
        Self {
            peripheral,
            phantom: PhantomData,
        }
    }

    fn regs(&self) -> &RegisterBlock {
        self.peripheral.register_block()
    }

    /// Read a byte from the UART in a non-blocking manner
    pub fn read_byte(&mut self) -> nb::Result<u8, Error> {
        // Check if there are any bytes to read
        if self
            .regs()
            .ep1_conf()
            .read()
            .serial_out_ep_data_avail()
            .bit_is_set()
        {
            let value = self.regs().ep1().read().rdwr_byte().bits();

            Ok(value)
        } else {
            Err(nb::Error::WouldBlock)
        }
    }

    /// Read all available bytes from the RX FIFO into the provided buffer and
    /// returns the number of read bytes. Never blocks. May stop early if the
    /// number of bytes in the FIFO is larger than `buf`.
    pub fn drain_rx_fifo(&mut self, buf: &mut [u8]) -> usize {
        let mut count = 0;
        while let Ok(value) = self.read_byte() {
            buf[count] = value;
            count += 1;
            if count == buf.len() {
                break;
            }
        }
        count
    }

    /// Listen for RX-PACKET-RECV interrupts
    pub fn listen_rx_packet_recv_interrupt(&mut self) {
        self.regs()
            .int_ena()
            .modify(|_, w| w.serial_out_recv_pkt().set_bit());
    }

    /// Stop listening for RX-PACKET-RECV interrupts
    pub fn unlisten_rx_packet_recv_interrupt(&mut self) {
        self.regs()
            .int_ena()
            .modify(|_, w| w.serial_out_recv_pkt().clear_bit());
    }

    /// Checks if RX-PACKET-RECV interrupt is set
    pub fn rx_packet_recv_interrupt_set(&mut self) -> bool {
        self.regs()
            .int_st()
            .read()
            .serial_out_recv_pkt()
            .bit_is_set()
    }

    /// Reset RX-PACKET-RECV interrupt
    pub fn reset_rx_packet_recv_interrupt(&mut self) {
        self.regs()
            .int_clr()
            .write(|w| w.serial_out_recv_pkt().clear_bit_by_one());
    }
}

impl<'d> UsbSerialJtag<'d, Blocking> {
    /// Create a new USB serial/JTAG instance with defaults
    pub fn new(usb_device: USB_DEVICE<'d>) -> Self {
        Self::new_inner(usb_device)
    }

    /// Reconfigure the USB Serial JTAG peripheral to operate in asynchronous
    /// mode.
    pub fn into_async(mut self) -> UsbSerialJtag<'d, Async> {
        self.set_interrupt_handler(async_interrupt_handler);

        UsbSerialJtag {
            rx: UsbSerialJtagRx {
                peripheral: self.rx.peripheral,
                phantom: PhantomData,
            },
            tx: UsbSerialJtagTx {
                peripheral: self.tx.peripheral,
                phantom: PhantomData,
            },
        }
    }
}

impl crate::private::Sealed for UsbSerialJtag<'_, Blocking> {}

#[instability::unstable]
impl crate::interrupt::InterruptConfigurable for UsbSerialJtag<'_, Blocking> {
    fn set_interrupt_handler(&mut self, handler: crate::interrupt::InterruptHandler) {
        self.set_interrupt_handler(handler);
    }
}

impl<'d, Dm> UsbSerialJtag<'d, Dm>
where
    Dm: DriverMode,
{
    fn new_inner(usb_device: USB_DEVICE<'d>) -> Self {
        // Do NOT reset the peripheral. Doing so will result in a broken USB JTAG
        // connection.
        if PeripheralClockControl::enable(Peripheral::UsbDevice) {
            PeripheralClockControl::reset(Peripheral::UsbDevice);
        } else {
            // Refcount was more than 0. Decrement to avoid overflow because we don't handle
            // dropping the driver.
            PeripheralClockControl::disable(Peripheral::UsbDevice);
        }

        usb_device.disable_tx_interrupts();
        usb_device.disable_rx_interrupts();

        #[cfg(any(esp32c3, esp32s3))]
        {
            use crate::efuse::USB_EXCHG_PINS;

            // On the esp32c3, and esp32s3 the USB_EXCHG_PINS efuse is bugged and
            // doesn't swap the pullups too, this works around that.
            if crate::efuse::read_bit(USB_EXCHG_PINS) {
                usb_device.register_block().conf0().modify(|_, w| {
                    w.pad_pull_override().set_bit();
                    w.dm_pullup().clear_bit();
                    w.dp_pullup().set_bit()
                });
            }
        }

        Self {
            rx: UsbSerialJtagRx::new_inner(unsafe { usb_device.clone_unchecked() }),
            tx: UsbSerialJtagTx::new_inner(usb_device),
        }
    }
    /// Split the USB Serial JTAG peripheral into a transmitter and receiver,
    /// which is particularly useful when having two tasks correlating to
    /// transmitting and receiving.
    pub fn split(self) -> (UsbSerialJtagRx<'d, Dm>, UsbSerialJtagTx<'d, Dm>) {
        (self.rx, self.tx)
    }

    /// Write data to the serial output in chunks of up to 64 bytes
    pub fn write(&mut self, data: &[u8]) -> Result<(), Error> {
        self.tx.write(data)
    }

    /// Write data to the serial output in a non-blocking manner
    /// Requires manual flushing (automatically flushed every 64 bytes)
    pub fn write_byte_nb(&mut self, word: u8) -> nb::Result<(), Error> {
        self.tx.write_byte_nb(word)
    }

    /// Flush the output FIFO and block until it has been sent
    pub fn flush_tx(&mut self) -> Result<(), Error> {
        self.tx.flush_tx()
    }

    /// Flush the output FIFO but don't block if it isn't ready immediately
    pub fn flush_tx_nb(&mut self) -> nb::Result<(), Error> {
        self.tx.flush_tx_nb()
    }

    /// Read a single byte but don't block if it isn't ready immediately
    pub fn read_byte(&mut self) -> nb::Result<u8, Error> {
        self.rx.read_byte()
    }

    /// Listen for RX-PACKET-RECV interrupts
    pub fn listen_rx_packet_recv_interrupt(&mut self) {
        self.rx.listen_rx_packet_recv_interrupt()
    }

    /// Stop listening for RX-PACKET-RECV interrupts
    pub fn unlisten_rx_packet_recv_interrupt(&mut self) {
        self.rx.unlisten_rx_packet_recv_interrupt()
    }

    /// Checks if RX-PACKET-RECV interrupt is set
    pub fn rx_packet_recv_interrupt_set(&mut self) -> bool {
        self.rx.rx_packet_recv_interrupt_set()
    }

    /// Reset RX-PACKET-RECV interrupt
    pub fn reset_rx_packet_recv_interrupt(&mut self) {
        self.rx.reset_rx_packet_recv_interrupt()
    }

    /// Registers an interrupt handler for the USB Serial JTAG peripheral.
    ///
    /// Note that this will replace any previously registered interrupt
    /// handlers.
    #[instability::unstable]
    pub fn set_interrupt_handler(&mut self, handler: crate::interrupt::InterruptHandler) {
        self.rx.peripheral.disable_peri_interrupt_on_all_cores();
        self.rx.peripheral.bind_peri_interrupt(handler);
    }
}

/// USB Serial/JTAG peripheral instance
#[doc(hidden)]
pub trait Instance: crate::private::Sealed {
    /// Get a reference to the peripheral's underlying register block
    fn register_block(&self) -> &RegisterBlock;

    /// Disable all transmit interrupts for the peripheral
    fn disable_tx_interrupts(&self) {
        self.register_block()
            .int_ena()
            .modify(|_, w| w.serial_in_empty().clear_bit());

        self.register_block()
            .int_clr()
            .write(|w| w.serial_in_empty().clear_bit_by_one());
    }

    /// Disable all receive interrupts for the peripheral
    fn disable_rx_interrupts(&self) {
        self.register_block()
            .int_ena()
            .modify(|_, w| w.serial_out_recv_pkt().clear_bit());

        self.register_block()
            .int_clr()
            .write(|w| w.serial_out_recv_pkt().clear_bit_by_one());
    }
}

impl Instance for USB_DEVICE<'_> {
    #[inline(always)]
    fn register_block(&self) -> &RegisterBlock {
        USB_DEVICE::regs()
    }
}

impl<Dm> core::fmt::Write for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    fn write_str(&mut self, s: &str) -> core::fmt::Result {
        core::fmt::Write::write_str(&mut self.tx, s)
    }
}

impl<Dm> core::fmt::Write for UsbSerialJtagTx<'_, Dm>
where
    Dm: DriverMode,
{
    fn write_str(&mut self, s: &str) -> core::fmt::Result {
        self.write(s.as_bytes()).map_err(|_| core::fmt::Error)?;
        Ok(())
    }
}

#[instability::unstable]
impl<Dm> ufmt_write::uWrite for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;

    #[inline]
    fn write_str(&mut self, s: &str) -> Result<(), Self::Error> {
        ufmt_write::uWrite::write_str(&mut self.tx, s)
    }

    #[inline]
    fn write_char(&mut self, ch: char) -> Result<(), Self::Error> {
        ufmt_write::uWrite::write_char(&mut self.tx, ch)
    }
}

#[instability::unstable]
impl<Dm> ufmt_write::uWrite for UsbSerialJtagTx<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;

    #[inline]
    fn write_str(&mut self, s: &str) -> Result<(), Self::Error> {
        self.write(s.as_bytes())?;
        Ok(())
    }

    #[inline]
    fn write_char(&mut self, ch: char) -> Result<(), Self::Error> {
        let mut buffer = [0u8; 4];
        self.write(ch.encode_utf8(&mut buffer).as_bytes())?;

        Ok(())
    }
}

#[instability::unstable]
impl<Dm> embedded_io_06::ErrorType for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;
}

#[instability::unstable]
impl<Dm> embedded_io_06::ErrorType for UsbSerialJtagTx<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;
}

#[instability::unstable]
impl<Dm> embedded_io_06::ErrorType for UsbSerialJtagRx<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;
}

#[instability::unstable]
impl<Dm> embedded_io_06::Read for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        embedded_io_06::Read::read(&mut self.rx, buf)
    }
}

#[instability::unstable]
impl<Dm> embedded_io_06::Read for UsbSerialJtagRx<'_, Dm>
where
    Dm: DriverMode,
{
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        loop {
            let count = self.drain_rx_fifo(buf);
            if count > 0 {
                return Ok(count);
            }
        }
    }
}

#[instability::unstable]
impl<Dm> embedded_io_06::Write for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        embedded_io_06::Write::write(&mut self.tx, buf)
    }

    fn flush(&mut self) -> Result<(), Self::Error> {
        embedded_io_06::Write::flush(&mut self.tx)
    }
}

#[instability::unstable]
impl<Dm> embedded_io_06::Write for UsbSerialJtagTx<'_, Dm>
where
    Dm: DriverMode,
{
    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        self.write(buf)?;

        Ok(buf.len())
    }

    fn flush(&mut self) -> Result<(), Self::Error> {
        self.flush_tx()
    }
}

#[instability::unstable]
impl<Dm> embedded_io_07::ErrorType for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;
}

#[instability::unstable]
impl<Dm> embedded_io_07::ErrorType for UsbSerialJtagTx<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;
}

#[instability::unstable]
impl<Dm> embedded_io_07::ErrorType for UsbSerialJtagRx<'_, Dm>
where
    Dm: DriverMode,
{
    type Error = Error;
}

#[instability::unstable]
impl<Dm> embedded_io_07::Read for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        embedded_io_07::Read::read(&mut self.rx, buf)
    }
}

#[instability::unstable]
impl<Dm> embedded_io_07::Read for UsbSerialJtagRx<'_, Dm>
where
    Dm: DriverMode,
{
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        loop {
            let count = self.drain_rx_fifo(buf);
            if count > 0 {
                return Ok(count);
            }
        }
    }
}

#[instability::unstable]
impl<Dm> embedded_io_07::Write for UsbSerialJtag<'_, Dm>
where
    Dm: DriverMode,
{
    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        embedded_io_07::Write::write(&mut self.tx, buf)
    }

    fn flush(&mut self) -> Result<(), Self::Error> {
        embedded_io_07::Write::flush(&mut self.tx)
    }
}

#[instability::unstable]
impl<Dm> embedded_io_07::Write for UsbSerialJtagTx<'_, Dm>
where
    Dm: DriverMode,
{
    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        self.write(buf)?;

        Ok(buf.len())
    }

    fn flush(&mut self) -> Result<(), Self::Error> {
        self.flush_tx()
    }
}

// Static instance of the waker for each component of the peripheral:
static WAKER_TX: AtomicWaker = AtomicWaker::new();
static WAKER_RX: AtomicWaker = AtomicWaker::new();

#[must_use = "futures do nothing unless you `.await` or poll them"]
struct UsbSerialJtagWriteFuture<'d> {
    peripheral: USB_DEVICE<'d>,
}

impl<'d> UsbSerialJtagWriteFuture<'d> {
    fn new(peripheral: USB_DEVICE<'d>) -> Self {
        // Set the interrupt enable bit for the USB_SERIAL_JTAG_SERIAL_IN_EMPTY_INT
        // interrupt
        peripheral
            .register_block()
            .int_ena()
            .modify(|_, w| w.serial_in_empty().set_bit());

        Self { peripheral }
    }

    fn event_bit_is_clear(&self) -> bool {
        self.peripheral
            .register_block()
            .int_ena()
            .read()
            .serial_in_empty()
            .bit_is_clear()
    }
}

impl core::future::Future for UsbSerialJtagWriteFuture<'_> {
    type Output = ();

    fn poll(
        self: core::pin::Pin<&mut Self>,
        cx: &mut core::task::Context<'_>,
    ) -> core::task::Poll<Self::Output> {
        WAKER_TX.register(cx.waker());
        if self.event_bit_is_clear() {
            Poll::Ready(())
        } else {
            Poll::Pending
        }
    }
}

#[must_use = "futures do nothing unless you `.await` or poll them"]
struct UsbSerialJtagReadFuture<'d> {
    peripheral: USB_DEVICE<'d>,
}

impl<'d> UsbSerialJtagReadFuture<'d> {
    fn new(peripheral: USB_DEVICE<'d>) -> Self {
        // Set the interrupt enable bit for the USB_SERIAL_JTAG_SERIAL_OUT_RECV_PKT
        // interrupt
        peripheral
            .register_block()
            .int_ena()
            .modify(|_, w| w.serial_out_recv_pkt().set_bit());

        Self { peripheral }
    }

    fn event_bit_is_clear(&self) -> bool {
        self.peripheral
            .register_block()
            .int_ena()
            .read()
            .serial_out_recv_pkt()
            .bit_is_clear()
    }
}

impl core::future::Future for UsbSerialJtagReadFuture<'_> {
    type Output = ();

    fn poll(
        self: core::pin::Pin<&mut Self>,
        cx: &mut core::task::Context<'_>,
    ) -> core::task::Poll<Self::Output> {
        WAKER_RX.register(cx.waker());
        if self.event_bit_is_clear() {
            Poll::Ready(())
        } else {
            Poll::Pending
        }
    }
}

impl<'d> UsbSerialJtag<'d, Async> {
    /// Reconfigure the USB Serial JTAG peripheral to operate in blocking
    /// mode.
    pub fn into_blocking(self) -> UsbSerialJtag<'d, Blocking> {
        self.rx.peripheral.disable_peri_interrupt_on_all_cores();
        UsbSerialJtag {
            rx: UsbSerialJtagRx {
                peripheral: self.rx.peripheral,
                phantom: PhantomData,
            },
            tx: UsbSerialJtagTx {
                peripheral: self.tx.peripheral,
                phantom: PhantomData,
            },
        }
    }
}

impl UsbSerialJtagTx<'_, Async> {
    async fn write_async(&mut self, words: &[u8]) -> Result<(), Error> {
        for chunk in words.chunks(64) {
            for byte in chunk {
                self.regs()
                    .ep1()
                    .write(|w| unsafe { w.rdwr_byte().bits(*byte) });
            }
            self.regs().ep1_conf().modify(|_, w| w.wr_done().set_bit());

            UsbSerialJtagWriteFuture::new(self.peripheral.reborrow()).await;
        }

        Ok(())
    }

    async fn flush_tx_async(&mut self) -> Result<(), Error> {
        if self
            .regs()
            .ep1_conf()
            .read()
            .serial_in_ep_data_free()
            .bit_is_clear()
        {
            UsbSerialJtagWriteFuture::new(self.peripheral.reborrow()).await;
        }

        Ok(())
    }
}

impl UsbSerialJtagRx<'_, Async> {
    async fn read_async(&mut self, buf: &mut [u8]) -> Result<usize, Error> {
        if buf.is_empty() {
            return Ok(0);
        }

        loop {
            let read = self.drain_rx_fifo(buf);
            if read > 0 {
                return Ok(read);
            }
            UsbSerialJtagReadFuture::new(self.peripheral.reborrow()).await;
        }
    }
}

#[instability::unstable]
impl embedded_io_async_06::Write for UsbSerialJtag<'_, Async> {
    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        embedded_io_async_06::Write::write(&mut self.tx, buf).await
    }

    async fn flush(&mut self) -> Result<(), Self::Error> {
        embedded_io_async_06::Write::flush(&mut self.tx).await
    }
}

#[instability::unstable]
impl embedded_io_async_06::Write for UsbSerialJtagTx<'_, Async> {
    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        self.write_async(buf).await?;

        Ok(buf.len())
    }

    async fn flush(&mut self) -> Result<(), Self::Error> {
        self.flush_tx_async().await
    }
}

#[instability::unstable]
impl embedded_io_async_06::Read for UsbSerialJtag<'_, Async> {
    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        embedded_io_async_06::Read::read(&mut self.rx, buf).await
    }
}

#[instability::unstable]
impl embedded_io_async_06::Read for UsbSerialJtagRx<'_, Async> {
    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        self.read_async(buf).await
    }
}
#[instability::unstable]
impl embedded_io_async_07::Write for UsbSerialJtag<'_, Async> {
    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        embedded_io_async_07::Write::write(&mut self.tx, buf).await
    }

    async fn flush(&mut self) -> Result<(), Self::Error> {
        embedded_io_async_07::Write::flush(&mut self.tx).await
    }
}

#[instability::unstable]
impl embedded_io_async_07::Write for UsbSerialJtagTx<'_, Async> {
    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
        self.write_async(buf).await?;

        Ok(buf.len())
    }

    async fn flush(&mut self) -> Result<(), Self::Error> {
        self.flush_tx_async().await
    }
}

#[instability::unstable]
impl embedded_io_async_07::Read for UsbSerialJtag<'_, Async> {
    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        embedded_io_async_07::Read::read(&mut self.rx, buf).await
    }
}

#[instability::unstable]
impl embedded_io_async_07::Read for UsbSerialJtagRx<'_, Async> {
    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
        self.read_async(buf).await
    }
}

#[handler]
fn async_interrupt_handler() {
    let usb = USB_DEVICE::regs();
    let interrupts = usb.int_st().read();

    let tx = interrupts.serial_in_empty().bit_is_set();
    let rx = interrupts.serial_out_recv_pkt().bit_is_set();

    if tx {
        usb.int_ena().modify(|_, w| w.serial_in_empty().clear_bit());
    }
    if rx {
        usb.int_ena()
            .modify(|_, w| w.serial_out_recv_pkt().clear_bit());
    }

    usb.int_clr().write(|w| {
        w.serial_in_empty()
            .clear_bit_by_one()
            .serial_out_recv_pkt()
            .clear_bit_by_one()
    });

    if rx {
        WAKER_RX.wake();
    }
    if tx {
        WAKER_TX.wake();
    }
}
