vcan_loopback/

vcan_loopback.rs

//! End-to-end SDO over a Linux `vcan0` virtual CAN bus — the first time the
//! SocketCAN transport actually executes on a bus (no hardware needed).
//!
//! A server thread exposes an object dictionary on `vcan0`; the main thread is
//! a client that reads and writes it, exercising both expedited and segmented
//! transfers. Because SocketCAN delivers every frame to all sockets bound to
//! the interface, the two ends simply share `vcan0`.
//!
//! Set up the interface first (see `tools/vcan_setup.sh`), then:
//!
//! ```text
//! cargo run -p canopen-host --example vcan_loopback
//! ```

fn main() {
    #[cfg(target_os = "linux")]
    {
        if let Err(e) = linux::run() {
            eprintln!("vcan_loopback FAILED: {e}");
            std::process::exit(1);
        }
    }
    #[cfg(not(target_os = "linux"))]
    {
        eprintln!("This example requires Linux SocketCAN (vcan0); see tools/vcan_setup.sh.");
    }
}

#[cfg(target_os = "linux")]
mod linux {
    use std::error::Error;
    use std::sync::mpsc;
    use std::thread;
    use std::time::Duration;

    use canopen_host::transport::{Received, SocketCan};
    use canopen_rs::node::{Node, MAX_PDO_MAPPING};
    use canopen_rs::sync::SYNC_COB_ID;
    use canopen_rs::{
        Address, DataType, Entry, MappingEntry, NmtCommand, NodeId, ObjectDictionary, PdoMapping,
        TransmissionType, Value,
    };

    const IFACE: &str = "vcan0";

    pub fn run() -> Result<(), Box<dyn Error>> {
        let node = NodeId::new(0x10)?;

        // --- Server node: serve an object dictionary on vcan0 in a thread. ---
        let (ready_tx, ready_rx) = mpsc::channel::<()>();
        thread::spawn(move || {
            if let Err(e) = serve(node, ready_tx) {
                eprintln!("server thread error: {e}");
            }
        });
        // Wait until the server socket is open and listening.
        ready_rx.recv().map_err(|_| "server failed to start")?;

        // --- Client: talk to the node over vcan0. ---
        let bus = SocketCan::open(IFACE)?;
        bus.set_read_timeout(Duration::from_secs(2))?;

        // Expedited read (4-byte object).
        let device_type = bus.sdo_read(node, Address::new(0x1000, 0), DataType::Unsigned32)?;
        println!("read  0x1000 device type      = {device_type:?}");
        assert_eq!(device_type, Value::Unsigned32(0x0004_0192));

        // Expedited write then read-back (2-byte object).
        bus.sdo_write(node, Address::new(0x1017, 0), Value::Unsigned16(2500))?;
        let heartbeat = bus.sdo_read(node, Address::new(0x1017, 0), DataType::Unsigned16)?;
        println!("write 0x1017 heartbeat -> read = {heartbeat:?}");
        assert_eq!(heartbeat, Value::Unsigned16(2500));

        // 8-byte object forces SEGMENTED transfer over the real bus.
        let big = Value::Unsigned64(0x0102_0304_0506_0708);
        bus.sdo_write(node, Address::new(0x2000, 0), big)?;
        let back = bus.sdo_read(node, Address::new(0x2000, 0), DataType::Unsigned64)?;
        println!("write 0x2000 (segmented) -> read = {back:?}");
        assert_eq!(back, big);

        // --- PDO: go operational, drive an RPDO in and a SYNC-triggered TPDO
        //     out. RPDO1 (0x200+node) writes 0x6000/1; TPDO1 (0x180+node) maps
        //     the same object, so a SYNC echoes back what the RPDO wrote. ---
        let rpdo1 = 0x200 + node.raw() as u16;
        let tpdo1 = 0x180 + node.raw() as u16;
        bus.send_nmt(NmtCommand::StartRemoteNode, node)?; // -> operational
        bus.send(rpdo1, &[0xCD, 0xAB])?; // RPDO1: 0x6000/1 <- 0xABCD
        bus.send(SYNC_COB_ID, &[])?; // SYNC: node emits synchronous TPDOs

        let tpdo = recv_cob(&bus, tpdo1)?;
        println!("RPDO in 0xABCD -> SYNC -> TPDO out = {:02X?}", tpdo.data());
        assert_eq!(tpdo.data(), &[0xCD, 0xAB]);

        println!(
            "\nvcan0 loopback OK — SDO (expedited + segmented), NMT, and PDO all round-tripped."
        );
        Ok(())
    }

    /// Receive frames until one arrives on `cob_id`.
    fn recv_cob(bus: &SocketCan, cob_id: u16) -> Result<Received, Box<dyn Error>> {
        loop {
            let frame = bus.recv()?;
            if frame.cob_id == cob_id {
                return Ok(frame);
            }
        }
    }

    /// A device node: build an OD, configure a PDO pair, boot, and serve frames
    /// (SDO, NMT, RPDO) plus SYNC-triggered TPDOs until the bus goes quiet.
    fn serve(node_id: NodeId, ready: mpsc::Sender<()>) -> Result<(), Box<dyn Error>> {
        let bus = SocketCan::open(IFACE)?;
        bus.set_read_timeout(Duration::from_secs(3))?;

        let mut od = ObjectDictionary::<8>::new();
        od.insert(
            Address::new(0x1000, 0),
            Entry::constant(Value::Unsigned32(0x0004_0192)),
        )?;
        od.insert(Address::new(0x1017, 0), Entry::rw(Value::Unsigned16(1000)))?;
        od.insert(Address::new(0x2000, 0), Entry::rw(Value::Unsigned64(0)))?;
        od.insert(Address::new(0x6000, 1), Entry::rw(Value::Unsigned16(0)))?;

        let mut node = Node::new(node_id, od);
        // RPDO1 receives into 0x6000/1; TPDO1 transmits it back on SYNC.
        node.add_rpdo(0x200 + node_id.raw() as u16, mapping(0x6000, 1, 16))?;
        node.add_tpdo(
            0x180 + node_id.raw() as u16,
            mapping(0x6000, 1, 16),
            TransmissionType::SynchronousAcyclic,
        )?;
        node.boot(); // enter pre-operational so SDO is served
        ready.send(()).map_err(|_| "client went away")?;

        // Serve until a read times out (the client is done and the bus is idle).
        while let Ok(frame) = bus.recv() {
            if let Some(tx) = node.on_frame(frame.cob_id, frame.data()) {
                bus.send(tx.cob_id, tx.data())?;
            }
            if frame.cob_id == SYNC_COB_ID {
                for tx in node.sync_tpdos() {
                    bus.send(tx.cob_id, tx.data())?;
                }
            }
        }
        Ok(())
    }

    /// A single-object PDO mapping.
    fn mapping(index: u16, subindex: u8, bits: u8) -> PdoMapping<MAX_PDO_MAPPING> {
        let mut m = PdoMapping::new();
        m.push(MappingEntry::new(index, subindex, bits))
            .expect("one entry fits");
        m
    }
}