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Add USB max packet size parameters to eusb v5 to support HS usb #140

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2929010
Add USB max packet size parameters to eusb v5
kevswims Sep 4, 2025
182a962
Add USB max packet size to examples
kevswims Sep 4, 2025
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9 changes: 7 additions & 2 deletions example/firmware/src/bin/comms-01.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ use postcard_rpc::{
server::{
impls::embassy_usb_v0_5::{
dispatch_impl::{WireRxBuf, WireRxImpl, WireSpawnImpl, WireStorage, WireTxImpl},
PacketBuffers,
PacketBuffers, USB_FS_MAX_PACKET_SIZE,
},
Dispatch, Server,
},
Expand Down Expand Up @@ -88,7 +88,12 @@ async fn main(spawner: Spawner) {
let config = usb_config();

let context = Context;
let (device, tx_impl, rx_impl) = STORAGE.init(driver, config, pbufs.tx_buf.as_mut_slice());
let (device, tx_impl, rx_impl) = STORAGE.init(
driver,
config,
pbufs.tx_buf.as_mut_slice(),
USB_FS_MAX_PACKET_SIZE,
);
let dispatcher = MyApp::new(context, spawner.into());
let vkk = dispatcher.min_key_len();
let mut server: AppServer = Server::new(
Expand Down
9 changes: 7 additions & 2 deletions example/firmware/src/bin/comms-02.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ use postcard_rpc::{
dispatch_impl::{
spawn_fn, WireRxBuf, WireRxImpl, WireSpawnImpl, WireStorage, WireTxImpl,
},
PacketBuffers,
PacketBuffers, USB_FS_MAX_PACKET_SIZE,
},
Dispatch, Sender, Server, SpawnContext,
},
Expand Down Expand Up @@ -162,7 +162,12 @@ async fn main(spawner: Spawner) {
accel: accel_ref,
};

let (device, tx_impl, rx_impl) = STORAGE.init(driver, config, pbufs.tx_buf.as_mut_slice());
let (device, tx_impl, rx_impl) = STORAGE.init(
driver,
config,
pbufs.tx_buf.as_mut_slice(),
USB_FS_MAX_PACKET_SIZE,
);

// Set timeout to 4ms/frame, instead of the default 2ms/frame
tx_impl.set_timeout_ms_per_frame(4).await;
Expand Down
9 changes: 7 additions & 2 deletions example/firmware/src/bin/logging.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ use postcard_rpc::{
server::{
impls::embassy_usb_v0_5::{
dispatch_impl::{WireRxBuf, WireRxImpl, WireSpawnImpl, WireStorage, WireTxImpl},
PacketBuffers,
PacketBuffers, USB_FS_MAX_PACKET_SIZE,
},
Dispatch, Sender, Server,
},
Expand Down Expand Up @@ -87,7 +87,12 @@ async fn main(spawner: Spawner) {

let context = Context {};

let (device, tx_impl, rx_impl) = STORAGE.init(driver, config, pbufs.tx_buf.as_mut_slice());
let (device, tx_impl, rx_impl) = STORAGE.init(
driver,
config,
pbufs.tx_buf.as_mut_slice(),
USB_FS_MAX_PACKET_SIZE,
);
let dispatcher = MyApp::new(context, spawner.into());
let vkk = dispatcher.min_key_len();
let server: AppServer = Server::new(
Expand Down
9 changes: 7 additions & 2 deletions example/firmware/src/bin/minimal.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ use postcard_rpc::{
server::{
impls::embassy_usb_v0_5::{
dispatch_impl::{WireRxBuf, WireRxImpl, WireSpawnImpl, WireStorage, WireTxImpl},
PacketBuffers,
PacketBuffers, USB_FS_MAX_PACKET_SIZE,
},
Dispatch, Server,
},
Expand Down Expand Up @@ -90,7 +90,12 @@ async fn main(spawner: Spawner) {

let context = Context {};

let (device, tx_impl, rx_impl) = STORAGE.init(driver, config, pbufs.tx_buf.as_mut_slice());
let (device, tx_impl, rx_impl) = STORAGE.init(
driver,
config,
pbufs.tx_buf.as_mut_slice(),
USB_FS_MAX_PACKET_SIZE,
);
let dispatcher = MyApp::new(context, spawner.into());
let vkk = dispatcher.min_key_len();
let server: AppServer = Server::new(
Expand Down
63 changes: 51 additions & 12 deletions source/postcard-rpc/src/server/impls/embassy_usb_v0_5.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,10 @@ static HDLR: ConstStaticCell<PoststationHandler> = ConstStaticCell::new(Poststat

/// Default time in milliseconds to wait for the completion of sending
pub const DEFAULT_TIMEOUT_MS_PER_FRAME: usize = 2;
/// Default max packet size for USB Full Speed
pub const USB_FS_MAX_PACKET_SIZE: usize = 64;
/// Default max packet size for USB High Speed
pub const USB_HS_MAX_PACKET_SIZE: usize = 512;

impl embassy_usb_0_5::Handler for PoststationHandler {
fn get_string(
Expand Down Expand Up @@ -110,6 +114,7 @@ pub mod dispatch_impl {
driver: D,
config: Config<'static>,
tx_buf: &'static mut [u8],
max_usb_frame_size: usize,
) -> (UsbDevice<'static, D>, WireTxImpl<M, D>, WireRxImpl<D>) {
let bufs = self.bufs_usb.take();

Expand Down Expand Up @@ -156,6 +161,7 @@ pub mod dispatch_impl {
tx_buf,
pending_frame: false,
timeout_ms_per_frame: DEFAULT_TIMEOUT_MS_PER_FRAME,
max_usb_frame_size: max_usb_frame_size,
}));

// Build the builder.
Expand All @@ -172,8 +178,10 @@ pub mod dispatch_impl {
driver: D,
config: Config<'static>,
tx_buf: &'static mut [u8],
max_usb_frame_size: usize,
) -> (UsbDevice<'static, D>, WireTxImpl<M, D>, WireRxImpl<D>) {
let (builder, wtx, wrx) = self.init_without_build(driver, config, tx_buf);
let (builder, wtx, wrx) =
self.init_without_build(driver, config, tx_buf, max_usb_frame_size);
let usb = builder.build();
(usb, wtx, wrx)
}
Expand All @@ -185,7 +193,9 @@ pub mod dispatch_impl {
driver: D,
config: Config<'static>,
tx_buf: &'static mut [u8],
max_usb_frame_size: usize,
) -> (Builder<'static, D>, WireTxImpl<M, D>, WireRxImpl<D>) {
assert!(max_usb_frame_size.is_power_of_two());
let bufs = self.bufs_usb.take();

let mut builder = Builder::new(
Expand Down Expand Up @@ -215,8 +225,8 @@ pub mod dispatch_impl {
let mut function = builder.function(0xFF, 0, 0);
let mut interface = function.interface();
let mut alt = interface.alt_setting(0xFF, 0, 0, None);
let ep_out = alt.endpoint_bulk_out(None, 64);
let ep_in = alt.endpoint_bulk_in(None, 64);
let ep_out = alt.endpoint_bulk_out(None, max_usb_frame_size as u16);
let ep_in = alt.endpoint_bulk_in(None, max_usb_frame_size as u16);
drop(function);

let wtx = self.cell.init(Mutex::new(EUsbWireTxInner {
Expand All @@ -225,6 +235,7 @@ pub mod dispatch_impl {
tx_buf,
pending_frame: false,
timeout_ms_per_frame: DEFAULT_TIMEOUT_MS_PER_FRAME,
max_usb_frame_size: max_usb_frame_size,
}));

(builder, EUsbWireTx { inner: wtx }, EUsbWireRx { ep_out })
Expand All @@ -243,6 +254,7 @@ pub struct EUsbWireTxInner<D: Driver<'static>> {
tx_buf: &'static mut [u8],
pending_frame: bool,
timeout_ms_per_frame: usize,
max_usb_frame_size: usize,
}

/// A [`WireTx`] implementation for embassy-usb 0.4.
Expand Down Expand Up @@ -313,14 +325,22 @@ impl<M: RawMutex + 'static, D: Driver<'static> + 'static> WireTx for EUsbWireTx<
tx_buf,
pending_frame,
timeout_ms_per_frame,
max_usb_frame_size,
}: &mut EUsbWireTxInner<D> = &mut inner;

let (hdr_used, remain) = hdr.write_to_slice(tx_buf).ok_or(WireTxErrorKind::Other)?;
let bdy_used = postcard::to_slice(msg, remain).map_err(|_| WireTxErrorKind::Other)?;
let used_ttl = hdr_used.len() + bdy_used.len();

if let Some(used) = tx_buf.get(..used_ttl) {
send_all::<D>(ep_in, used, pending_frame, *timeout_ms_per_frame).await
send_all::<D>(
ep_in,
used,
pending_frame,
*timeout_ms_per_frame,
*max_usb_frame_size,
)
.await
} else {
Err(WireTxErrorKind::Other)
}
Expand All @@ -332,9 +352,17 @@ impl<M: RawMutex + 'static, D: Driver<'static> + 'static> WireTx for EUsbWireTx<
ep_in,
pending_frame,
timeout_ms_per_frame,
max_usb_frame_size,
..
}: &mut EUsbWireTxInner<D> = &mut inner;
send_all::<D>(ep_in, buf, pending_frame, *timeout_ms_per_frame).await
send_all::<D>(
ep_in,
buf,
pending_frame,
*timeout_ms_per_frame,
*max_usb_frame_size,
)
.await
}

async fn send_log_str(&self, kkind: VarKeyKind, s: &str) -> Result<(), Self::Error> {
Expand All @@ -346,6 +374,7 @@ impl<M: RawMutex + 'static, D: Driver<'static> + 'static> WireTx for EUsbWireTx<
tx_buf,
pending_frame,
timeout_ms_per_frame,
max_usb_frame_size,
}: &mut EUsbWireTxInner<D> = &mut inner;

let key = match kkind {
Expand All @@ -366,7 +395,14 @@ impl<M: RawMutex + 'static, D: Driver<'static> + 'static> WireTx for EUsbWireTx<
let used_ttl = hdr_used.len() + bdy_used.len();

if let Some(used) = tx_buf.get(..used_ttl) {
send_all::<D>(ep_in, used, pending_frame, *timeout_ms_per_frame).await
send_all::<D>(
ep_in,
used,
pending_frame,
*timeout_ms_per_frame,
*max_usb_frame_size,
)
.await
} else {
Err(WireTxErrorKind::Other)
}
Expand All @@ -385,6 +421,7 @@ impl<M: RawMutex + 'static, D: Driver<'static> + 'static> WireTx for EUsbWireTx<
tx_buf,
pending_frame,
timeout_ms_per_frame,
max_usb_frame_size,
}: &mut EUsbWireTxInner<D> = &mut inner;
let ttl_len = tx_buf.len();

Expand Down Expand Up @@ -460,6 +497,7 @@ impl<M: RawMutex + 'static, D: Driver<'static> + 'static> WireTx for EUsbWireTx<
&tx_buf[..act_used],
pending_frame,
*timeout_ms_per_frame,
*max_usb_frame_size,
)
.await
}
Expand All @@ -471,6 +509,7 @@ async fn send_all<D>(
out: &[u8],
pending_frame: &mut bool,
timeout_ms_per_frame: usize,
max_usb_frame_size: usize,
) -> Result<(), WireTxErrorKind>
where
D: Driver<'static>,
Expand All @@ -481,7 +520,7 @@ where

// Calculate an estimated timeout based on the number of frames we need to send
// For now, we use 2ms/frame by default, rounded UP
let frames = (out.len() + 63) / 64;
let frames = out.len().div_ceil(max_usb_frame_size);
let timeout_ms = frames * timeout_ms_per_frame;

let send_fut = async {
Expand All @@ -492,17 +531,17 @@ where
}
*pending_frame = true;

// write in segments of 64. The last chunk may
// be 0 < len <= 64.
for ch in out.chunks(64) {
// write in segments of max_usb_frame_size. The last chunk may
// be 0 < len <= max_usb_frame_size.
for ch in out.chunks(max_usb_frame_size) {
if ep_in.write(ch).await.is_err() {
return Err(WireTxErrorKind::ConnectionClosed);
}
}
// If the total we sent was a multiple of 64, send an
// If the total we sent was a multiple of max_usb_frame_size, send an
// empty message to "flush" the transaction. We already checked
// above that the len != 0.
if (out.len() & (64 - 1)) == 0 && ep_in.write(&[]).await.is_err() {
if (out.len() & (max_usb_frame_size - 1)) == 0 && ep_in.write(&[]).await.is_err() {
return Err(WireTxErrorKind::ConnectionClosed);
}

Expand Down
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