Merge #711

711: Add DeviceStateHandler, DeviceCommand channel, and remote wakeup support r=Dirbaio a=alexmoon

Apologies for the size of this PR. Once I started getting into the Vbus power management side of my device I found a couple of areas of functionality missing from embassy-usb. Specifically, I need the application to be able to respond to changes in the USB device state in order to properly control the amount of power I'm drawing from Vbus. I also wanted to enable remote wakeup support for my device.

In order to enable device state monitoring, I've created a `DeviceStateHandler` trait and made it possible to pass in an optional reference a handler implementing that trait when creating the `UsbDeviceBuilder`.

Remote wakeup required a way to send commands to the bus which is exclusively owned by the `UsbDevice::run` method. This is the same problem we were discussing for enabling/disabling the device on Vbus power events. My solution is to allow an optional `Channel` to be provided to the `UsbDeviceBuilder` (via `UsbDeviceBuilder::new_with_channel`), allowing the application to send commands into the `run` method. Right now it supports enable, disable and remote wakeup commands.

Since there's now a way to dynamically enable and disable the device, I also added `Config::start_enabled` to control whether or not the `UsbDevice` should start in the enabled state. That also allowed me to make `UsbDeviceBuilder::build` sync again and move enabling the bus into `UsbDevice::run`.

This led to a few driver changes:
1. `Driver::enable` became `Driver::into_bus`
2. `Bus::enable`, `Bus::disable`, and `Bus::remote_wakeup` were added
3. I removed `Bus::reset`, `Bus::suspend`, and `Bus::resume` because they were only ever called based on the result of `Bus::poll`. It made more sense to me to have `Bus::poll` handle the driver-specific state management itself.

I've updated the `usb_hid_keyboard` example to take advantage of all these additional features.

Let me know what you think.

Thanks!


Co-authored-by: alexmoon <alex.r.moon@gmail.com>

embassy-nrf/src/usb.rs

@@ -10,7 +10,7 @@ use embassy::util::Unborrow;
 use embassy::waitqueue::AtomicWaker;
 use embassy_hal_common::unborrow;
 use embassy_usb::control::Request;
-use embassy_usb::driver::{self, EndpointError, Event};
+use embassy_usb::driver::{self, EndpointError, Event, Unsupported};
 use embassy_usb::types::{EndpointAddress, EndpointInfo, EndpointType, UsbDirection};
 use futures::future::poll_fn;
 use futures::Future;
@@ -140,7 +140,6 @@ impl<'d, T: Instance> driver::Driver<'d> for Driver<'d, T> {
     type EndpointIn = Endpoint<'d, T, In>;
     type ControlPipe = ControlPipe<'d, T>;
     type Bus = Bus<'d, T>;
-    type EnableFuture = impl Future<Output = Self::Bus> + 'd;
 
     fn alloc_endpoint_in(
         &mut self,
@@ -192,7 +191,28 @@ impl<'d, T: Instance> driver::Driver<'d> for Driver<'d, T> {
         })
     }
 
-    fn enable(self) -> Self::EnableFuture {
+    fn into_bus(self) -> Self::Bus {
+        Bus {
+            phantom: PhantomData,
+            alloc_in: self.alloc_in,
+            alloc_out: self.alloc_out,
+        }
+    }
+}
+
+pub struct Bus<'d, T: Instance> {
+    phantom: PhantomData<&'d mut T>,
+    alloc_in: Allocator,
+    alloc_out: Allocator,
+}
+
+impl<'d, T: Instance> driver::Bus for Bus<'d, T> {
+    type EnableFuture<'a> = impl Future<Output = ()> + 'a where Self: 'a;
+    type DisableFuture<'a> = impl Future<Output = ()> + 'a where Self: 'a;
+    type PollFuture<'a> = impl Future<Output = Event> + 'a where Self: 'a;
+    type RemoteWakeupFuture<'a> = impl Future<Output = Result<(), Unsupported>> + 'a where Self: 'a;
+
+    fn enable(&mut self) -> Self::EnableFuture<'_> {
         async move {
             let regs = T::regs();
 
@@ -226,33 +246,25 @@ impl<'d, T: Instance> driver::Driver<'d> for Driver<'d, T> {
             // Enable the USB pullup, allowing enumeration.
             regs.usbpullup.write(|w| w.connect().enabled());
             trace!("enabled");
-
-            Bus {
-                phantom: PhantomData,
-                alloc_in: self.alloc_in,
-                alloc_out: self.alloc_out,
         }
     }
+
+    fn disable(&mut self) -> Self::DisableFuture<'_> {
+        async move {
+            let regs = T::regs();
+            regs.enable.write(|x| x.enable().disabled());
+        }
     }
-}
-
-pub struct Bus<'d, T: Instance> {
-    phantom: PhantomData<&'d mut T>,
-    alloc_in: Allocator,
-    alloc_out: Allocator,
-}
-
-impl<'d, T: Instance> driver::Bus for Bus<'d, T> {
-    type PollFuture<'a> = impl Future<Output = Event> + 'a where Self: 'a;
 
     fn poll<'a>(&'a mut self) -> Self::PollFuture<'a> {
-        poll_fn(|cx| {
+        poll_fn(move |cx| {
             BUS_WAKER.register(cx.waker());
             let regs = T::regs();
 
             if regs.events_usbreset.read().bits() != 0 {
                 regs.events_usbreset.reset();
                 regs.intenset.write(|w| w.usbreset().set());
+                self.set_configured(false);
                 return Poll::Ready(Event::Reset);
             }
 
@@ -268,11 +280,12 @@ impl<'d, T: Instance> driver::Bus for Bus<'d, T> {
             }
             if r.suspend().bit() {
                 regs.eventcause.write(|w| w.suspend().set_bit());
-                trace!("USB event: suspend");
+                regs.lowpower.write(|w| w.lowpower().low_power());
+                return Poll::Ready(Event::Suspend);
             }
             if r.resume().bit() {
                 regs.eventcause.write(|w| w.resume().set_bit());
-                trace!("USB event: resume");
+                return Poll::Ready(Event::Resume);
             }
             if r.ready().bit() {
                 regs.eventcause.write(|w| w.ready().set_bit());
@@ -283,11 +296,6 @@ impl<'d, T: Instance> driver::Bus for Bus<'d, T> {
         })
     }
 
-    #[inline]
-    fn reset(&mut self) {
-        self.set_configured(false);
-    }
-
     #[inline]
     fn set_configured(&mut self, configured: bool) {
         let regs = T::regs();
@@ -343,18 +351,43 @@ impl<'d, T: Instance> driver::Bus for Bus<'d, T> {
     }
 
     #[inline]
-    fn suspend(&mut self) {
+    fn remote_wakeup(&mut self) -> Self::RemoteWakeupFuture<'_> {
-        let regs = T::regs();
+        async move {
-        regs.lowpower.write(|w| w.lowpower().low_power());
-    }
-
-    #[inline]
-    fn resume(&mut self) {
             let regs = T::regs();
 
+            if regs.lowpower.read().lowpower().is_low_power() {
                 errata::pre_wakeup();
 
                 regs.lowpower.write(|w| w.lowpower().force_normal());
+
+                poll_fn(|cx| {
+                    BUS_WAKER.register(cx.waker());
+                    let regs = T::regs();
+                    let r = regs.eventcause.read();
+
+                    if regs.events_usbreset.read().bits() != 0 {
+                        Poll::Ready(())
+                    } else if r.resume().bit() {
+                        Poll::Ready(())
+                    } else if r.usbwuallowed().bit() {
+                        regs.eventcause.write(|w| w.usbwuallowed().set_bit());
+
+                        regs.dpdmvalue.write(|w| w.state().resume());
+                        regs.tasks_dpdmdrive
+                            .write(|w| w.tasks_dpdmdrive().set_bit());
+
+                        Poll::Ready(())
+                    } else {
+                        Poll::Pending
+                    }
+                })
+                .await;
+
+                errata::post_wakeup();
+            }
+
+            Ok(())
+        }
     }
 }
 
@@ -834,17 +867,20 @@ macro_rules! impl_usb {
 mod errata {
 
     /// Writes `val` to `addr`. Used to apply Errata workarounds.
+    #[cfg(any(feature = "nrf52840", feature = "nrf52833", feature = "nrf52820"))]
     unsafe fn poke(addr: u32, val: u32) {
         (addr as *mut u32).write_volatile(val);
     }
 
     /// Reads 32 bits from `addr`.
+    #[cfg(feature = "nrf52840")]
     unsafe fn peek(addr: u32) -> u32 {
         (addr as *mut u32).read_volatile()
     }
 
     pub fn pre_enable() {
         // Works around Erratum 187 on chip revisions 1 and 2.
+        #[cfg(any(feature = "nrf52840", feature = "nrf52833", feature = "nrf52820"))]
         unsafe {
             poke(0x4006EC00, 0x00009375);
             poke(0x4006ED14, 0x00000003);
@@ -858,6 +894,7 @@ mod errata {
         post_wakeup();
 
         // Works around Erratum 187 on chip revisions 1 and 2.
+        #[cfg(any(feature = "nrf52840", feature = "nrf52833", feature = "nrf52820"))]
         unsafe {
             poke(0x4006EC00, 0x00009375);
             poke(0x4006ED14, 0x00000000);
@@ -868,6 +905,7 @@ mod errata {
     pub fn pre_wakeup() {
         // Works around Erratum 171 on chip revisions 1 and 2.
 
+        #[cfg(feature = "nrf52840")]
         unsafe {
             if peek(0x4006EC00) == 0x00000000 {
                 poke(0x4006EC00, 0x00009375);
@@ -881,6 +919,7 @@ mod errata {
     pub fn post_wakeup() {
         // Works around Erratum 171 on chip revisions 1 and 2.
 
+        #[cfg(feature = "nrf52840")]
         unsafe {
             if peek(0x4006EC00) == 0x00000000 {
                 poke(0x4006EC00, 0x00009375);

embassy-usb/src/builder.rs

@@ -4,6 +4,7 @@ use super::control::ControlHandler;
 use super::descriptor::{BosWriter, DescriptorWriter};
 use super::driver::{Driver, EndpointAllocError};
 use super::types::*;
+use super::DeviceStateHandler;
 use super::UsbDevice;
 use super::MAX_INTERFACE_COUNT;
 
@@ -119,6 +120,7 @@ impl<'a> Config<'a> {
 /// Used to build new [`UsbDevice`]s.
 pub struct UsbDeviceBuilder<'d, D: Driver<'d>> {
     config: Config<'d>,
+    handler: Option<&'d dyn DeviceStateHandler>,
     interfaces: Vec<(u8, &'d mut dyn ControlHandler), MAX_INTERFACE_COUNT>,
     control_buf: &'d mut [u8],
 
@@ -145,6 +147,7 @@ impl<'d, D: Driver<'d>> UsbDeviceBuilder<'d, D> {
         config_descriptor_buf: &'d mut [u8],
         bos_descriptor_buf: &'d mut [u8],
         control_buf: &'d mut [u8],
+        handler: Option<&'d dyn DeviceStateHandler>,
     ) -> Self {
         // Magic values specified in USB-IF ECN on IADs.
         if config.composite_with_iads
@@ -174,6 +177,7 @@ impl<'d, D: Driver<'d>> UsbDeviceBuilder<'d, D> {
 
         UsbDeviceBuilder {
             driver,
+            handler,
             config,
             interfaces: Vec::new(),
             control_buf,
@@ -187,20 +191,20 @@ impl<'d, D: Driver<'d>> UsbDeviceBuilder<'d, D> {
     }
 
     /// Creates the [`UsbDevice`] instance with the configuration in this builder.
-    pub async fn build(mut self) -> UsbDevice<'d, D> {
+    pub fn build(mut self) -> UsbDevice<'d, D> {
         self.config_descriptor.end_configuration();
         self.bos_descriptor.end_bos();
 
         UsbDevice::build(
             self.driver,
             self.config,
+            self.handler,
             self.device_descriptor.into_buf(),
             self.config_descriptor.into_buf(),
             self.bos_descriptor.writer.into_buf(),
             self.interfaces,
             self.control_buf,
         )
-        .await
     }
 
     /// Allocates a new interface number.

embassy-usb/src/driver.rs

@@ -11,7 +11,6 @@ pub trait Driver<'a> {
     type EndpointIn: EndpointIn + 'a;
     type ControlPipe: ControlPipe + 'a;
     type Bus: Bus + 'a;
-    type EnableFuture: Future<Output = Self::Bus> + 'a;
 
     /// Allocates an endpoint and specified endpoint parameters. This method is called by the device
     /// and class implementations to allocate endpoints, and can only be called before
@@ -47,7 +46,7 @@ pub trait Driver<'a> {
 
     /// Enables and initializes the USB peripheral. Soon after enabling the device will be reset, so
     /// there is no need to perform a USB reset in this method.
-    fn enable(self) -> Self::EnableFuture;
+    fn into_bus(self) -> Self::Bus;
 
     /// Indicates that `set_device_address` must be called before accepting the corresponding
     /// control transfer, not after.
@@ -57,19 +56,28 @@ pub trait Driver<'a> {
 }
 
 pub trait Bus {
+    type EnableFuture<'a>: Future<Output = ()> + 'a
+    where
+        Self: 'a;
+    type DisableFuture<'a>: Future<Output = ()> + 'a
+    where
+        Self: 'a;
     type PollFuture<'a>: Future<Output = Event> + 'a
     where
         Self: 'a;
+    type RemoteWakeupFuture<'a>: Future<Output = Result<(), Unsupported>> + 'a
+    where
+        Self: 'a;
+
+    /// Enables the USB peripheral. Soon after enabling the device will be reset, so
+    /// there is no need to perform a USB reset in this method.
+    fn enable(&mut self) -> Self::EnableFuture<'_>;
+
+    /// Disables and powers down the USB peripheral.
+    fn disable(&mut self) -> Self::DisableFuture<'_>;
 
     fn poll<'a>(&'a mut self) -> Self::PollFuture<'a>;
 
-    /// Called when the host resets the device. This will be soon called after
-    /// [`poll`](crate::device::UsbDevice::poll) returns [`PollResult::Reset`]. This method should
-    /// reset the state of all endpoints and peripheral flags back to a state suitable for
-    /// enumeration, as well as ensure that all endpoints previously allocated with alloc_ep are
-    /// initialized as specified.
-    fn reset(&mut self);
-
     /// Sets the device USB address to `addr`.
     fn set_device_address(&mut self, addr: u8);
 
@@ -83,17 +91,6 @@ pub trait Bus {
     /// Gets whether the STALL condition is set for an endpoint. Only used during control transfers.
     fn is_stalled(&mut self, ep_addr: EndpointAddress) -> bool;
 
-    /// Causes the USB peripheral to enter USB suspend mode, lowering power consumption and
-    /// preparing to detect a USB wakeup event. This will be called after
-    /// [`poll`](crate::device::UsbDevice::poll) returns [`PollResult::Suspend`]. The device will
-    /// continue be polled, and it shall return a value other than `Suspend` from `poll` when it no
-    /// longer detects the suspend condition.
-    fn suspend(&mut self);
-
-    /// Resumes from suspend mode. This may only be called after the peripheral has been previously
-    /// suspended.
-    fn resume(&mut self);
-
     /// Simulates a disconnect from the USB bus, causing the host to reset and re-enumerate the
     /// device.
     ///
@@ -106,6 +103,14 @@ pub trait Bus {
     fn force_reset(&mut self) -> Result<(), Unsupported> {
         Err(Unsupported)
     }
+
+    /// Initiates a remote wakeup of the host by the device.
+    ///
+    /// # Errors
+    ///
+    /// * [`Unsupported`](crate::UsbError::Unsupported) - This UsbBus implementation doesn't support
+    ///   remote wakeup or it has not been enabled at creation time.
+    fn remote_wakeup(&mut self) -> Self::RemoteWakeupFuture<'_>;
 }
 
 pub trait Endpoint {

embassy-usb/src/lib.rs

@@ -10,15 +10,14 @@ pub mod control;
 pub mod descriptor;
 pub mod driver;
 pub mod types;
-mod util;
 
+use embassy::util::{select, Either};
 use heapless::Vec;
 
 use self::control::*;
 use self::descriptor::*;
 use self::driver::{Bus, Driver, Event};
 use self::types::*;
-use self::util::*;
 
 pub use self::builder::Config;
 pub use self::builder::UsbDeviceBuilder;
@@ -28,8 +27,12 @@ pub use self::builder::UsbDeviceBuilder;
 /// In general class traffic is only possible in the `Configured` state.
 #[repr(u8)]
 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum UsbDeviceState {
-    /// The USB device has just been created or reset.
+    /// The USB device is disabled.
+    Disabled,
+
+    /// The USB device has just been enabled or reset.
     Default,
 
     /// The USB device has received an address from the host.
@@ -37,9 +40,19 @@ pub enum UsbDeviceState {
 
     /// The USB device has been configured and is fully functional.
     Configured,
+}
 
-    /// The USB device has been suspended by the host or it has been unplugged from the USB bus.
+#[derive(PartialEq, Eq, Copy, Clone, Debug)]
-    Suspend,
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum RemoteWakeupError {
+    InvalidState,
+    Unsupported,
+}
+
+impl From<driver::Unsupported> for RemoteWakeupError {
+    fn from(_: driver::Unsupported) -> Self {
+        RemoteWakeupError::Unsupported
+    }
 }
 
 /// The bConfiguration value for the not configured state.
@@ -53,8 +66,30 @@ pub const DEFAULT_ALTERNATE_SETTING: u8 = 0;
 
 pub const MAX_INTERFACE_COUNT: usize = 4;
 
+/// A handler trait for changes in the device state of the [UsbDevice].
+pub trait DeviceStateHandler {
+    /// Called when the USB device has been enabled or disabled.
+    fn enabled(&self, _enabled: bool) {}
+
+    /// Called when the host resets the device.
+    fn reset(&self) {}
+
+    /// Called when the host has set the address of the device to `addr`.
+    fn addressed(&self, _addr: u8) {}
+
+    /// Called when the host has enabled or disabled the configuration of the device.
+    fn configured(&self, _configured: bool) {}
+
+    /// Called when the bus has entered or exited the suspend state.
+    fn suspended(&self, _suspended: bool) {}
+
+    /// Called when remote wakeup feature is enabled or disabled.
+    fn remote_wakeup_enabled(&self, _enabled: bool) {}
+}
+
 pub struct UsbDevice<'d, D: Driver<'d>> {
     bus: D::Bus,
+    handler: Option<&'d dyn DeviceStateHandler>,
     control: ControlPipe<D::ControlPipe>,
 
     config: Config<'d>,
@@ -64,6 +99,7 @@ pub struct UsbDevice<'d, D: Driver<'d>> {
     control_buf: &'d mut [u8],
 
     device_state: UsbDeviceState,
+    suspended: bool,
     remote_wakeup_enabled: bool,
     self_powered: bool,
     pending_address: u8,
@@ -72,9 +108,10 @@ pub struct UsbDevice<'d, D: Driver<'d>> {
 }
 
 impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
-    pub(crate) async fn build(
+    pub(crate) fn build(
         mut driver: D,
         config: Config<'d>,
+        handler: Option<&'d dyn DeviceStateHandler>,
         device_descriptor: &'d [u8],
         config_descriptor: &'d [u8],
         bos_descriptor: &'d [u8],
@@ -87,17 +124,19 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
 
         // Enable the USB bus.
         // This prevent further allocation by consuming the driver.
-        let bus = driver.enable().await;
+        let bus = driver.into_bus();
 
         Self {
             bus,
             config,
+            handler,
             control: ControlPipe::new(control),
             device_descriptor,
             config_descriptor,
             bos_descriptor,
             control_buf,
-            device_state: UsbDeviceState::Default,
+            device_state: UsbDeviceState::Disabled,
+            suspended: false,
             remote_wakeup_enabled: false,
             self_powered: false,
             pending_address: 0,
@@ -105,37 +144,130 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
         }
     }
 
-    pub async fn run(&mut self) {
+    /// Runs the `UsbDevice` forever.
+    ///
+    /// This future may leave the bus in an invalid state if it is dropped.
+    /// After dropping the future, [`UsbDevice::disable()`] should be called
+    /// before calling any other `UsbDevice` methods to fully reset the
+    /// peripheral.
+    pub async fn run(&mut self) -> ! {
+        loop {
+            self.run_until_suspend().await;
+            self.wait_resume().await;
+        }
+    }
+
+    /// Runs the `UsbDevice` until the bus is suspended.
+    ///
+    /// This future may leave the bus in an invalid state if it is dropped.
+    /// After dropping the future, [`UsbDevice::disable()`] should be called
+    /// before calling any other `UsbDevice` methods to fully reset the
+    /// peripheral.
+    pub async fn run_until_suspend(&mut self) -> () {
+        if self.device_state == UsbDeviceState::Disabled {
+            self.bus.enable().await;
+            self.device_state = UsbDeviceState::Default;
+
+            if let Some(h) = &self.handler {
+                h.enabled(true);
+            }
+        }
+
         loop {
             let control_fut = self.control.setup();
             let bus_fut = self.bus.poll();
             match select(bus_fut, control_fut).await {
-                Either::Left(evt) => match evt {
+                Either::First(evt) => {
+                    self.handle_bus_event(evt);
+                    if self.suspended {
+                        return;
+                    }
+                }
+                Either::Second(req) => match req {
+                    Setup::DataIn(req, stage) => self.handle_control_in(req, stage).await,
+                    Setup::DataOut(req, stage) => self.handle_control_out(req, stage).await,
+                },
+            }
+        }
+    }
+
+    /// Disables the USB peripheral.
+    pub async fn disable(&mut self) {
+        if self.device_state != UsbDeviceState::Disabled {
+            self.bus.disable().await;
+            self.device_state = UsbDeviceState::Disabled;
+            self.suspended = false;
+            self.remote_wakeup_enabled = false;
+
+            if let Some(h) = &self.handler {
+                h.enabled(false);
+            }
+        }
+    }
+
+    /// Waits for a resume condition on the USB bus.
+    ///
+    /// This future is cancel-safe.
+    pub async fn wait_resume(&mut self) {
+        while self.suspended {
+            let evt = self.bus.poll().await;
+            self.handle_bus_event(evt);
+        }
+    }
+
+    /// Initiates a device remote wakeup on the USB bus.
+    ///
+    /// If the bus is not suspended or remote wakeup is not enabled, an error
+    /// will be returned.
+    ///
+    /// This future may leave the bus in an inconsistent state if dropped.
+    /// After dropping the future, [`UsbDevice::disable()`] should be called
+    /// before calling any other `UsbDevice` methods to fully reset the peripheral.
+    pub async fn remote_wakeup(&mut self) -> Result<(), RemoteWakeupError> {
+        if self.suspended && self.remote_wakeup_enabled {
+            self.bus.remote_wakeup().await?;
+            self.suspended = false;
+
+            if let Some(h) = &self.handler {
+                h.suspended(false);
+            }
+
+            Ok(())
+        } else {
+            Err(RemoteWakeupError::InvalidState)
+        }
+    }
+
+    fn handle_bus_event(&mut self, evt: Event) {
+        match evt {
             Event::Reset => {
                 trace!("usb: reset");
-                        self.bus.reset();
-
                 self.device_state = UsbDeviceState::Default;
+                self.suspended = false;
                 self.remote_wakeup_enabled = false;
                 self.pending_address = 0;
 
                 for (_, h) in self.interfaces.iter_mut() {
                     h.reset();
                 }
+
+                if let Some(h) = &self.handler {
+                    h.reset();
+                }
             }
             Event::Resume => {
                 trace!("usb: resume");
+                self.suspended = false;
+                if let Some(h) = &self.handler {
+                    h.suspended(false);
+                }
             }
             Event::Suspend => {
                 trace!("usb: suspend");
-                        self.bus.suspend();
+                self.suspended = true;
-                        self.device_state = UsbDeviceState::Suspend;
+                if let Some(h) = &self.handler {
+                    h.suspended(true);
                 }
-                },
-                Either::Right(req) => match req {
-                    Setup::DataIn(req, stage) => self.handle_control_in(req, stage).await,
-                    Setup::DataOut(req, stage) => self.handle_control_out(req, stage).await,
-                },
             }
         }
     }
@@ -156,20 +288,33 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
             (RequestType::Standard, Recipient::Device) => match (req.request, req.value) {
                 (Request::CLEAR_FEATURE, Request::FEATURE_DEVICE_REMOTE_WAKEUP) => {
                     self.remote_wakeup_enabled = false;
+                    if let Some(h) = &self.handler {
+                        h.remote_wakeup_enabled(false);
+                    }
                     self.control.accept(stage)
                 }
                 (Request::SET_FEATURE, Request::FEATURE_DEVICE_REMOTE_WAKEUP) => {
                     self.remote_wakeup_enabled = true;
+                    if let Some(h) = &self.handler {
+                        h.remote_wakeup_enabled(true);
+                    }
                     self.control.accept(stage)
                 }
                 (Request::SET_ADDRESS, addr @ 1..=127) => {
                     self.pending_address = addr as u8;
                     self.bus.set_device_address(self.pending_address);
+                    self.device_state = UsbDeviceState::Addressed;
+                    if let Some(h) = &self.handler {
+                        h.addressed(self.pending_address);
+                    }
                     self.control.accept(stage)
                 }
                 (Request::SET_CONFIGURATION, CONFIGURATION_VALUE_U16) => {
                     self.device_state = UsbDeviceState::Configured;
                     self.bus.set_configured(true);
+                    if let Some(h) = &self.handler {
+                        h.configured(true);
+                    }
                     self.control.accept(stage)
                 }
                 (Request::SET_CONFIGURATION, CONFIGURATION_NONE_U16) => match self.device_state {
@@ -177,6 +322,9 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
                     _ => {
                         self.device_state = UsbDeviceState::Addressed;
                         self.bus.set_configured(false);
+                        if let Some(h) = &self.handler {
+                            h.configured(false);
+                        }
                         self.control.accept(stage)
                     }
                 },

embassy-usb/src/util.rs

@@ -1,45 +0,0 @@
-use core::future::Future;
-use core::pin::Pin;
-use core::task::{Context, Poll};
-
-#[derive(Debug, Clone)]
-pub enum Either<A, B> {
-    Left(A),
-    Right(B),
-}
-
-pub fn select<A, B>(a: A, b: B) -> Select<A, B>
-where
-    A: Future,
-    B: Future,
-{
-    Select { a, b }
-}
-
-pub struct Select<A, B> {
-    a: A,
-    b: B,
-}
-
-impl<A: Unpin, B: Unpin> Unpin for Select<A, B> {}
-
-impl<A, B> Future for Select<A, B>
-where
-    A: Future,
-    B: Future,
-{
-    type Output = Either<A::Output, B::Output>;
-
-    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        let this = unsafe { self.get_unchecked_mut() };
-        let a = unsafe { Pin::new_unchecked(&mut this.a) };
-        let b = unsafe { Pin::new_unchecked(&mut this.b) };
-        match a.poll(cx) {
-            Poll::Ready(x) => Poll::Ready(Either::Left(x)),
-            Poll::Pending => match b.poll(cx) {
-                Poll::Ready(x) => Poll::Ready(Either::Right(x)),
-                Poll::Pending => Poll::Pending,
-            },
-        }
-    }
-}

examples/nrf/src/bin/usb_hid_keyboard.rs

@@ -4,16 +4,20 @@
 #![feature(type_alias_impl_trait)]
 
 use core::mem;
+use core::sync::atomic::{AtomicBool, Ordering};
 use defmt::*;
+use embassy::channel::Signal;
 use embassy::executor::Spawner;
+use embassy::interrupt::InterruptExt;
 use embassy::time::Duration;
+use embassy::util::{select, select3, Either, Either3};
 use embassy_nrf::gpio::{Input, Pin, Pull};
 use embassy_nrf::interrupt;
 use embassy_nrf::pac;
 use embassy_nrf::usb::Driver;
 use embassy_nrf::Peripherals;
 use embassy_usb::control::OutResponse;
-use embassy_usb::{Config, UsbDeviceBuilder};
+use embassy_usb::{Config, DeviceStateHandler, UsbDeviceBuilder};
 use embassy_usb_hid::{HidClass, ReportId, RequestHandler, State};
 use futures::future::join;
 use usbd_hid::descriptor::{KeyboardReport, SerializedDescriptor};
@@ -21,6 +25,25 @@ use usbd_hid::descriptor::{KeyboardReport, SerializedDescriptor};
 use defmt_rtt as _; // global logger
 use panic_probe as _;
 
+static ENABLE_USB: Signal<bool> = Signal::new();
+static SUSPENDED: AtomicBool = AtomicBool::new(false);
+
+fn on_power_interrupt(_: *mut ()) {
+    let regs = unsafe { &*pac::POWER::ptr() };
+
+    if regs.events_usbdetected.read().bits() != 0 {
+        regs.events_usbdetected.reset();
+        info!("Vbus detected, enabling USB...");
+        ENABLE_USB.signal(true);
+    }
+
+    if regs.events_usbremoved.read().bits() != 0 {
+        regs.events_usbremoved.reset();
+        info!("Vbus removed, disabling USB...");
+        ENABLE_USB.signal(false);
+    }
+}
+
 #[embassy::main]
 async fn main(_spawner: Spawner, p: Peripherals) {
     let clock: pac::CLOCK = unsafe { mem::transmute(()) };
@@ -30,10 +53,6 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     clock.tasks_hfclkstart.write(|w| unsafe { w.bits(1) });
     while clock.events_hfclkstarted.read().bits() != 1 {}
 
-    info!("Waiting for vbus...");
-    while !power.usbregstatus.read().vbusdetect().is_vbus_present() {}
-    info!("vbus OK");
-
     // Create the driver, from the HAL.
     let irq = interrupt::take!(USBD);
     let driver = Driver::new(p.USBD, irq);
@@ -45,6 +64,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     config.serial_number = Some("12345678");
     config.max_power = 100;
     config.max_packet_size_0 = 64;
+    config.supports_remote_wakeup = true;
 
     // Create embassy-usb DeviceBuilder using the driver and config.
     // It needs some buffers for building the descriptors.
@@ -53,6 +73,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     let mut bos_descriptor = [0; 256];
     let mut control_buf = [0; 16];
     let request_handler = MyRequestHandler {};
+    let device_state_handler = MyDeviceStateHandler::new();
 
     let mut state = State::<8, 1>::new();
 
@@ -63,6 +84,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
         &mut config_descriptor,
         &mut bos_descriptor,
         &mut control_buf,
+        Some(&device_state_handler),
     );
 
     // Create classes on the builder.
@@ -76,10 +98,40 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     );
 
     // Build the builder.
-    let mut usb = builder.build().await;
+    let mut usb = builder.build();
+
+    let remote_wakeup = Signal::new();
 
     // Run the USB device.
-    let usb_fut = usb.run();
+    let usb_fut = async {
+        enable_command().await;
+        loop {
+            match select(usb.run_until_suspend(), ENABLE_USB.wait()).await {
+                Either::First(_) => {}
+                Either::Second(enable) => {
+                    if enable {
+                        warn!("Enable when already enabled!");
+                    } else {
+                        usb.disable().await;
+                        enable_command().await;
+                    }
+                }
+            }
+
+            match select3(usb.wait_resume(), ENABLE_USB.wait(), remote_wakeup.wait()).await {
+                Either3::First(_) => (),
+                Either3::Second(enable) => {
+                    if enable {
+                        warn!("Enable when already enabled!");
+                    } else {
+                        usb.disable().await;
+                        enable_command().await;
+                    }
+                }
+                Either3::Third(_) => unwrap!(usb.remote_wakeup().await),
+            }
+        }
+    };
 
     let mut button = Input::new(p.P0_11.degrade(), Pull::Up);
 
@@ -90,6 +142,11 @@ async fn main(_spawner: Spawner, p: Peripherals) {
         loop {
             button.wait_for_low().await;
             info!("PRESSED");
+
+            if SUSPENDED.load(Ordering::Acquire) {
+                info!("Triggering remote wakeup");
+                remote_wakeup.signal(());
+            } else {
                 let report = KeyboardReport {
                     keycodes: [4, 0, 0, 0, 0, 0],
                     leds: 0,
@@ -100,6 +157,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
                     Ok(()) => {}
                     Err(e) => warn!("Failed to send report: {:?}", e),
                 };
+            }
 
             button.wait_for_high().await;
             info!("RELEASED");
@@ -119,11 +177,31 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     let out_fut = async {
         hid_out.run(false, &request_handler).await;
     };
+
+    let power_irq = interrupt::take!(POWER_CLOCK);
+    power_irq.set_handler(on_power_interrupt);
+    power_irq.unpend();
+    power_irq.enable();
+
+    power
+        .intenset
+        .write(|w| w.usbdetected().set().usbremoved().set());
+
     // Run everything concurrently.
     // If we had made everything `'static` above instead, we could do this using separate tasks instead.
     join(usb_fut, join(in_fut, out_fut)).await;
 }
 
+async fn enable_command() {
+    loop {
+        if ENABLE_USB.wait().await {
+            break;
+        } else {
+            warn!("Received disable signal when already disabled!");
+        }
+    }
+}
+
 struct MyRequestHandler {}
 
 impl RequestHandler for MyRequestHandler {
@@ -146,3 +224,64 @@ impl RequestHandler for MyRequestHandler {
         None
     }
 }
+
+struct MyDeviceStateHandler {
+    configured: AtomicBool,
+}
+
+impl MyDeviceStateHandler {
+    fn new() -> Self {
+        MyDeviceStateHandler {
+            configured: AtomicBool::new(false),
+        }
+    }
+}
+
+impl DeviceStateHandler for MyDeviceStateHandler {
+    fn enabled(&self, enabled: bool) {
+        self.configured.store(false, Ordering::Relaxed);
+        SUSPENDED.store(false, Ordering::Release);
+        if enabled {
+            info!("Device enabled");
+        } else {
+            info!("Device disabled");
+        }
+    }
+
+    fn reset(&self) {
+        self.configured.store(false, Ordering::Relaxed);
+        info!("Bus reset, the Vbus current limit is 100mA");
+    }
+
+    fn addressed(&self, addr: u8) {
+        self.configured.store(false, Ordering::Relaxed);
+        info!("USB address set to: {}", addr);
+    }
+
+    fn configured(&self, configured: bool) {
+        self.configured.store(configured, Ordering::Relaxed);
+        if configured {
+            info!(
+                "Device configured, it may now draw up to the configured current limit from Vbus."
+            )
+        } else {
+            info!("Device is no longer configured, the Vbus current limit is 100mA.");
+        }
+    }
+
+    fn suspended(&self, suspended: bool) {
+        if suspended {
+            info!("Device suspended, the Vbus current limit is 500µA (or 2.5mA for high-power devices with remote wakeup enabled).");
+            SUSPENDED.store(true, Ordering::Release);
+        } else {
+            SUSPENDED.store(false, Ordering::Release);
+            if self.configured.load(Ordering::Relaxed) {
+                info!(
+                    "Device resumed, it may now draw up to the configured current limit from Vbus"
+                );
+            } else {
+                info!("Device resumed, the Vbus current limit is 100mA");
+            }
+        }
+    }
+}

examples/nrf/src/bin/usb_hid_mouse.rs

@@ -61,6 +61,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
         &mut config_descriptor,
         &mut bos_descriptor,
         &mut control_buf,
+        None,
     );
 
     // Create classes on the builder.
@@ -74,7 +75,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     );
 
     // Build the builder.
-    let mut usb = builder.build().await;
+    let mut usb = builder.build();
 
     // Run the USB device.
     let usb_fut = usb.run();

examples/nrf/src/bin/usb_serial.rs

@@ -54,13 +54,14 @@ async fn main(_spawner: Spawner, p: Peripherals) {
         &mut config_descriptor,
         &mut bos_descriptor,
         &mut control_buf,
+        None,
     );
 
     // Create classes on the builder.
     let mut class = CdcAcmClass::new(&mut builder, &mut state, 64);
 
     // Build the builder.
-    let mut usb = builder.build().await;
+    let mut usb = builder.build();
 
     // Run the USB device.
     let usb_fut = usb.run();

examples/nrf/src/bin/usb_serial_multitask.rs

@@ -79,13 +79,14 @@ async fn main(spawner: Spawner, p: Peripherals) {
         &mut res.config_descriptor,
         &mut res.bos_descriptor,
         &mut res.control_buf,
+        None,
     );
 
     // Create classes on the builder.
     let class = CdcAcmClass::new(&mut builder, &mut res.serial_state, 64);
 
     // Build the builder.
-    let usb = builder.build().await;
+    let usb = builder.build();
 
     unwrap!(spawner.spawn(usb_task(usb)));
     unwrap!(spawner.spawn(echo_task(class)));