3 files changed, 338 insertions, 0 deletions

diff --git a/embassy-usb/src/class/midi.rs b/embassy-usb/src/class/midi.rs
new file mode 100644
index 000000000..c5cf8d876
--- /dev/null
+++ b/embassy-usb/src/class/midi.rs
@@ -0,0 +1,227 @@
+//! MIDI class implementation.
+
+use crate::driver::{Driver, Endpoint, EndpointError, EndpointIn, EndpointOut};
+use crate::Builder;
+
+/// This should be used as `device_class` when building the `UsbDevice`.
+pub const USB_AUDIO_CLASS: u8 = 0x01;
+
+const USB_AUDIOCONTROL_SUBCLASS: u8 = 0x01;
+const USB_MIDISTREAMING_SUBCLASS: u8 = 0x03;
+const MIDI_IN_JACK_SUBTYPE: u8 = 0x02;
+const MIDI_OUT_JACK_SUBTYPE: u8 = 0x03;
+const EMBEDDED: u8 = 0x01;
+const EXTERNAL: u8 = 0x02;
+const CS_INTERFACE: u8 = 0x24;
+const CS_ENDPOINT: u8 = 0x25;
+const HEADER_SUBTYPE: u8 = 0x01;
+const MS_HEADER_SUBTYPE: u8 = 0x01;
+const MS_GENERAL: u8 = 0x01;
+const PROTOCOL_NONE: u8 = 0x00;
+const MIDI_IN_SIZE: u8 = 0x06;
+const MIDI_OUT_SIZE: u8 = 0x09;
+
+/// Packet level implementation of a USB MIDI device.
+///
+/// This class can be used directly and it has the least overhead due to directly reading and
+/// writing USB packets with no intermediate buffers, but it will not act like a stream-like port.
+/// The following constraints must be followed if you use this class directly:
+///
+/// - `read_packet` must be called with a buffer large enough to hold max_packet_size bytes.
+/// - `write_packet` must not be called with a buffer larger than max_packet_size bytes.
+/// - If you write a packet that is exactly max_packet_size bytes long, it won't be processed by the
+///   host operating system until a subsequent shorter packet is sent. A zero-length packet (ZLP)
+///   can be sent if there is no other data to send. This is because USB bulk transactions must be
+///   terminated with a short packet, even if the bulk endpoint is used for stream-like data.
+pub struct MidiClass<'d, D: Driver<'d>> {
+    read_ep: D::EndpointOut,
+    write_ep: D::EndpointIn,
+}
+
+impl<'d, D: Driver<'d>> MidiClass<'d, D> {
+    /// Creates a new MidiClass with the provided UsbBus, number of input and output jacks and max_packet_size in bytes.
+    /// For full-speed devices, max_packet_size has to be one of 8, 16, 32 or 64.
+    pub fn new(builder: &mut Builder<'d, D>, n_in_jacks: u8, n_out_jacks: u8, max_packet_size: u16) -> Self {
+        let mut func = builder.function(USB_AUDIO_CLASS, USB_AUDIOCONTROL_SUBCLASS, PROTOCOL_NONE);
+
+        // Audio control interface
+        let mut iface = func.interface();
+        let audio_if = iface.interface_number();
+        let midi_if = u8::from(audio_if) + 1;
+        let mut alt = iface.alt_setting(USB_AUDIO_CLASS, USB_AUDIOCONTROL_SUBCLASS, PROTOCOL_NONE, None);
+        alt.descriptor(CS_INTERFACE, &[HEADER_SUBTYPE, 0x00, 0x01, 0x09, 0x00, 0x01, midi_if]);
+
+        // MIDIStreaming interface
+        let mut iface = func.interface();
+        let _midi_if = iface.interface_number();
+        let mut alt = iface.alt_setting(USB_AUDIO_CLASS, USB_MIDISTREAMING_SUBCLASS, PROTOCOL_NONE, None);
+
+        let midi_streaming_total_length = 7
+            + (n_in_jacks + n_out_jacks) as usize * (MIDI_IN_SIZE + MIDI_OUT_SIZE) as usize
+            + 7
+            + (4 + n_out_jacks as usize)
+            + 7
+            + (4 + n_in_jacks as usize);
+
+        alt.descriptor(
+            CS_INTERFACE,
+            &[
+                MS_HEADER_SUBTYPE,
+                0x00,
+                0x01,
+                (midi_streaming_total_length & 0xFF) as u8,
+                ((midi_streaming_total_length >> 8) & 0xFF) as u8,
+            ],
+        );
+
+        // Calculates the index'th external midi in jack id
+        let in_jack_id_ext = |index| 2 * index + 1;
+        // Calculates the index'th embedded midi out jack id
+        let out_jack_id_emb = |index| 2 * index + 2;
+        // Calculates the index'th external midi out jack id
+        let out_jack_id_ext = |index| 2 * n_in_jacks + 2 * index + 1;
+        // Calculates the index'th embedded midi in jack id
+        let in_jack_id_emb = |index| 2 * n_in_jacks + 2 * index + 2;
+
+        for i in 0..n_in_jacks {
+            alt.descriptor(CS_INTERFACE, &[MIDI_IN_JACK_SUBTYPE, EXTERNAL, in_jack_id_ext(i), 0x00]);
+        }
+
+        for i in 0..n_out_jacks {
+            alt.descriptor(CS_INTERFACE, &[MIDI_IN_JACK_SUBTYPE, EMBEDDED, in_jack_id_emb(i), 0x00]);
+        }
+
+        for i in 0..n_out_jacks {
+            alt.descriptor(
+                CS_INTERFACE,
+                &[
+                    MIDI_OUT_JACK_SUBTYPE,
+                    EXTERNAL,
+                    out_jack_id_ext(i),
+                    0x01,
+                    in_jack_id_emb(i),
+                    0x01,
+                    0x00,
+                ],
+            );
+        }
+
+        for i in 0..n_in_jacks {
+            alt.descriptor(
+                CS_INTERFACE,
+                &[
+                    MIDI_OUT_JACK_SUBTYPE,
+                    EMBEDDED,
+                    out_jack_id_emb(i),
+                    0x01,
+                    in_jack_id_ext(i),
+                    0x01,
+                    0x00,
+                ],
+            );
+        }
+
+        let mut endpoint_data = [
+            MS_GENERAL, 0, // Number of jacks
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // Jack mappings
+        ];
+        endpoint_data[1] = n_out_jacks;
+        for i in 0..n_out_jacks {
+            endpoint_data[2 + i as usize] = in_jack_id_emb(i);
+        }
+        let read_ep = alt.endpoint_bulk_out(max_packet_size);
+        alt.descriptor(CS_ENDPOINT, &endpoint_data[0..2 + n_out_jacks as usize]);
+
+        endpoint_data[1] = n_in_jacks;
+        for i in 0..n_in_jacks {
+            endpoint_data[2 + i as usize] = out_jack_id_emb(i);
+        }
+        let write_ep = alt.endpoint_bulk_in(max_packet_size);
+        alt.descriptor(CS_ENDPOINT, &endpoint_data[0..2 + n_in_jacks as usize]);
+
+        MidiClass { read_ep, write_ep }
+    }
+
+    /// Gets the maximum packet size in bytes.
+    pub fn max_packet_size(&self) -> u16 {
+        // The size is the same for both endpoints.
+        self.read_ep.info().max_packet_size
+    }
+
+    /// Writes a single packet into the IN endpoint.
+    pub async fn write_packet(&mut self, data: &[u8]) -> Result<(), EndpointError> {
+        self.write_ep.write(data).await
+    }
+
+    /// Reads a single packet from the OUT endpoint.
+    pub async fn read_packet(&mut self, data: &mut [u8]) -> Result<usize, EndpointError> {
+        self.read_ep.read(data).await
+    }
+
+    /// Waits for the USB host to enable this interface
+    pub async fn wait_connection(&mut self) {
+        self.read_ep.wait_enabled().await
+    }
+
+    /// Split the class into a sender and receiver.
+    ///
+    /// This allows concurrently sending and receiving packets from separate tasks.
+    pub fn split(self) -> (Sender<'d, D>, Receiver<'d, D>) {
+        (
+            Sender {
+                write_ep: self.write_ep,
+            },
+            Receiver { read_ep: self.read_ep },
+        )
+    }
+}
+
+/// Midi class packet sender.
+///
+/// You can obtain a `Sender` with [`MidiClass::split`]
+pub struct Sender<'d, D: Driver<'d>> {
+    write_ep: D::EndpointIn,
+}
+
+impl<'d, D: Driver<'d>> Sender<'d, D> {
+    /// Gets the maximum packet size in bytes.
+    pub fn max_packet_size(&self) -> u16 {
+        // The size is the same for both endpoints.
+        self.write_ep.info().max_packet_size
+    }
+
+    /// Writes a single packet.
+    pub async fn write_packet(&mut self, data: &[u8]) -> Result<(), EndpointError> {
+        self.write_ep.write(data).await
+    }
+
+    /// Waits for the USB host to enable this interface
+    pub async fn wait_connection(&mut self) {
+        self.write_ep.wait_enabled().await
+    }
+}
+
+/// Midi class packet receiver.
+///
+/// You can obtain a `Receiver` with [`MidiClass::split`]
+pub struct Receiver<'d, D: Driver<'d>> {
+    read_ep: D::EndpointOut,
+}
+
+impl<'d, D: Driver<'d>> Receiver<'d, D> {
+    /// Gets the maximum packet size in bytes.
+    pub fn max_packet_size(&self) -> u16 {
+        // The size is the same for both endpoints.
+        self.read_ep.info().max_packet_size
+    }
+
+    /// Reads a single packet.
+    pub async fn read_packet(&mut self, data: &mut [u8]) -> Result<usize, EndpointError> {
+        self.read_ep.read(data).await
+    }
+
+    /// Waits for the USB host to enable this interface
+    pub async fn wait_connection(&mut self) {
+        self.read_ep.wait_enabled().await
+    }
+}
diff --git a/embassy-usb/src/class/mod.rs b/embassy-usb/src/class/mod.rs
index b23e03d40..452eedf17 100644
--- a/embassy-usb/src/class/mod.rs
+++ b/embassy-usb/src/class/mod.rs
@@ -2,3 +2,4 @@
 pub mod cdc_acm;
 pub mod cdc_ncm;
 pub mod hid;
+pub mod midi;
diff --git a/examples/rp/src/bin/usb_midi.rs b/examples/rp/src/bin/usb_midi.rs
new file mode 100644
index 000000000..f0b03c81b
--- /dev/null
+++ b/examples/rp/src/bin/usb_midi.rs
@@ -0,0 +1,110 @@
+//! This example shows how to use USB (Universal Serial Bus) in the RP2040 chip.
+//!
+//! This creates a USB MIDI device that echoes MIDI messages back to the host.
+
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::{info, panic};
+use embassy_executor::Spawner;
+use embassy_futures::join::join;
+use embassy_rp::bind_interrupts;
+use embassy_rp::peripherals::USB;
+use embassy_rp::usb::{Driver, Instance, InterruptHandler};
+use embassy_usb::class::midi::MidiClass;
+use embassy_usb::driver::EndpointError;
+use embassy_usb::{Builder, Config};
+use {defmt_rtt as _, panic_probe as _};
+
+bind_interrupts!(struct Irqs {
+    USBCTRL_IRQ => InterruptHandler<USB>;
+});
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    info!("Hello world!");
+
+    let p = embassy_rp::init(Default::default());
+
+    // Create the driver, from the HAL.
+    let driver = Driver::new(p.USB, Irqs);
+
+    // Create embassy-usb Config
+    let mut config = Config::new(0xc0de, 0xcafe);
+    config.manufacturer = Some("Embassy");
+    config.product = Some("USB-MIDI example");
+    config.serial_number = Some("12345678");
+    config.max_power = 100;
+    config.max_packet_size_0 = 64;
+
+    // Required for windows compatibility.
+    // https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.9.1/kconfig/CONFIG_CDC_ACM_IAD.html#help
+    config.device_class = 0xEF;
+    config.device_sub_class = 0x02;
+    config.device_protocol = 0x01;
+    config.composite_with_iads = true;
+
+    // Create embassy-usb DeviceBuilder using the driver and config.
+    // It needs some buffers for building the descriptors.
+    let mut device_descriptor = [0; 256];
+    let mut config_descriptor = [0; 256];
+    let mut bos_descriptor = [0; 256];
+    let mut control_buf = [0; 64];
+
+    let mut builder = Builder::new(
+        driver,
+        config,
+        &mut device_descriptor,
+        &mut config_descriptor,
+        &mut bos_descriptor,
+        &mut control_buf,
+    );
+
+    // Create classes on the builder.
+    let mut class = MidiClass::new(&mut builder, 1, 1, 64);
+
+    // The `MidiClass` can be split into `Sender` and `Receiver`, to be used in separate tasks.
+    // let (sender, receiver) = class.split();
+
+    // Build the builder.
+    let mut usb = builder.build();
+
+    // Run the USB device.
+    let usb_fut = usb.run();
+
+    // Use the Midi class!
+    let midi_fut = async {
+        loop {
+            class.wait_connection().await;
+            info!("Connected");
+            let _ = midi_echo(&mut class).await;
+            info!("Disconnected");
+        }
+    };
+
+    // Run everything concurrently.
+    // If we had made everything `'static` above instead, we could do this using separate tasks instead.
+    join(usb_fut, midi_fut).await;
+}
+
+struct Disconnected {}
+
+impl From<EndpointError> for Disconnected {
+    fn from(val: EndpointError) -> Self {
+        match val {
+            EndpointError::BufferOverflow => panic!("Buffer overflow"),
+            EndpointError::Disabled => Disconnected {},
+        }
+    }
+}
+
+async fn midi_echo<'d, T: Instance + 'd>(class: &mut MidiClass<'d, Driver<'d, T>>) -> Result<(), Disconnected> {
+    let mut buf = [0; 64];
+    loop {
+        let n = class.read_packet(&mut buf).await?;
+        let data = &buf[..n];
+        info!("data: {:x}", data);
+        class.write_packet(data).await?;
+    }
+}