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