69 lines
2.3 KiB
Rust
69 lines
2.3 KiB
Rust
#![no_std]
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#![no_main]
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use defmt::*;
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use embassy_executor::Spawner;
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use embassy_stm32::bind_interrupts;
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use embassy_stm32::can::filter::Mask32;
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use embassy_stm32::can::{
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Can, Fifo, Frame, Rx0InterruptHandler, Rx1InterruptHandler, SceInterruptHandler, StandardId, TxInterruptHandler,
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};
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use embassy_stm32::gpio::{Input, Pull};
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use embassy_stm32::peripherals::CAN1;
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use embassy_time::Instant;
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use {defmt_rtt as _, panic_probe as _};
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bind_interrupts!(struct Irqs {
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CAN1_RX0 => Rx0InterruptHandler<CAN1>;
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CAN1_RX1 => Rx1InterruptHandler<CAN1>;
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CAN1_SCE => SceInterruptHandler<CAN1>;
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CAN1_TX => TxInterruptHandler<CAN1>;
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});
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#[embassy_executor::main]
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async fn main(_spawner: Spawner) {
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info!("Hello World!");
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let mut p = embassy_stm32::init(Default::default());
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// The next two lines are a workaround for testing without transceiver.
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// To synchronise to the bus the RX input needs to see a high level.
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// Use `mem::forget()` to release the borrow on the pin but keep the
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// pull-up resistor enabled.
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let rx_pin = Input::new(p.PA11.reborrow(), Pull::Up);
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core::mem::forget(rx_pin);
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let mut can = Can::new(p.CAN1, p.PA11, p.PA12, Irqs);
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can.modify_filters().enable_bank(0, Fifo::Fifo0, Mask32::accept_all());
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can.modify_config()
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.set_loopback(true) // Receive own frames
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.set_silent(true)
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.set_bitrate(1_000_000);
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can.enable().await;
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let mut i: u8 = 0;
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loop {
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let tx_frame = Frame::new_data(unwrap!(StandardId::new(i as _)), &[i]).unwrap();
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let tx_ts = Instant::now();
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can.write(&tx_frame).await;
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let envelope = can.read().await.unwrap();
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// We can measure loopback latency by using receive timestamp in the `Envelope`.
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// Our frame is ~55 bits long (exlcuding bit stuffing), so at 1mbps loopback delay is at least 55 us.
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// When measured with `tick-hz-1_000_000` actual latency is 80~83 us, giving a combined hardware and software
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// overhead of ~25 us. Note that CPU frequency can greatly affect the result.
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let latency = envelope.ts.saturating_duration_since(tx_ts);
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info!(
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"loopback frame {=u8}, latency: {} us",
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envelope.frame.data()[0],
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latency.as_micros()
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);
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i = i.wrapping_add(1);
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}
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}
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