Initial proof of concept

node/src/stm32/usb.rs

@@ -0,0 +1,41 @@
+// The library will have build errors when built on its own (due to not having embassy-stm32 feature for a specific microcontroller)
+// but it will work fine when used as a dependency for firmware that has the feature for a specific stm32 microcontroller.
+
+use crate::comms;
+use embassy_stm32::peripherals::USB_OTG_FS;
+use embassy_stm32::usb_otg::{Driver, Endpoint, In, Out};
+use embassy_usb::driver::{EndpointIn, EndpointOut};
+use embassy_usb::UsbDevice;
+
+pub type TypedUSB = UsbDevice<'static, Driver<'static, USB_OTG_FS>>;
+pub type TypedInterIn = Endpoint<'static, USB_OTG_FS, In>;
+pub type TypedInterOut = Endpoint<'static, USB_OTG_FS, Out>;
+
+pub struct UsbIO {
+    /// Send to master
+    pub interrupt_in: TypedInterIn,
+    /// Recieve from master
+    pub interrupt_out: TypedInterOut,
+}
+
+impl comms::Sender for TypedInterIn {
+    async fn send(&mut self, msg: &[u8]) -> Result<(), comms::Reset> {
+        self.write(msg).await.map_err(|_| comms::Reset)
+    }
+}
+
+impl comms::Receiver for TypedInterOut {
+    #[cfg(feature = "single-packet-msgs")]
+    async fn receive(&mut self, buffer: &mut [u8]) -> Result<(), comms::Reset> {
+        // This is OK when all our messages are smaller than a single packet.
+        self.read(buffer)
+            .await
+            .map(|_| ())
+            .map_err(|_| comms::Reset)
+    }
+
+    #[cfg(not(feature = "single-packet-msgs"))]
+    async fn receive(&mut self, buffer: &mut [u8]) -> Result<(), comms::Reset> {
+        todo!("Decide if we want a general purpose multi-packet message receive")
+    }
+}