ethercat-linux/src/bridge.rs

//! EL6695 bridge bring-up (J1900/primary side).
//!
//! Hard-won firmware constraints (all verified on hardware in the reference
//! project, kept identical here):
//! - The EL6695 user OD is wiped by the firmware whenever the master changes,
//!   so configuration and the data loop must happen in the same session.
//! - Mapping objects must be written with a Complete Access download in a
//!   single mailbox message; the standard initiate+segments flow is rejected
//!   with MBXERR_INVALIDSIZE.
//! - The PDO layout must replicate the TwinCAT secondary-side OD byte for
//!   byte: 0x1608/0x1A08 with 35 entries = [real object @240bit]
//!   + 33 x [0x0000:00 @240bit continuation] + 1 x [0x0000:00 @32bit],
//!   i.e. 8192 bit hanging on a single object (0x7000:01 / 0x6000:01).
//! - 0x1C12 = [0x1608]; 0x1C13 = [0x1A01 or 0x1A02, 0x1A08].
//! - SM registers and the AL state machine are driven with raw fpwr/fprd,
//!   bypassing ethercrab's CoE PDO parsing entirely.
//! - After SAFEOP the mailbox dies: no SDO traffic inside the data loop.

use ethercrab::{Command, MainDevice};
use std::time::Duration;

use crate::regs;

/// TwinCAT line-format 35-entry blob: first entry is the real object at
/// 240 bit, then 33 continuation entries at 240 bit, final entry 32 bit.
/// Entry format = [len_bits: u8, sub: u8, idx_lo: u8, idx_hi: u8].
fn twin_layout_blob(obj: u16) -> Vec<u8> {
    let mut blob = Vec::with_capacity(2 + 35 * 4);
    blob.extend_from_slice(&35u16.to_le_bytes());
    blob.extend_from_slice(&[240, 1, (obj & 0xFF) as u8, (obj >> 8) as u8]);
    for _ in 0..33 {
        blob.extend_from_slice(&[240, 0, 0, 0]);
    }
    blob.extend_from_slice(&[32, 0, 0, 0]);
    blob
}

/// SM assign blob: entry count (u16 LE) + mapped object indices.
fn assign_blob(objs: &[u16]) -> Vec<u8> {
    let mut blob = Vec::with_capacity(2 + objs.len() * 2);
    blob.extend_from_slice(&(objs.len() as u16).to_le_bytes());
    for &o in objs {
        blob.extend_from_slice(&o.to_le_bytes());
    }
    blob
}

/// Complete Access write of a whole object, 3 attempts.
async fn sdo_ca<S>(sd: &ethercrab::SubDeviceRef<'_, S>, idx: u16, blob: &[u8]) -> bool
where
    S: std::ops::Deref<Target = ethercrab::SubDevice>,
{
    for attempt in 0..3 {
        match sd.sdo_write_complete(idx, 0, blob).await {
            Ok(_) => return true,
            Err(e) => {
                if attempt == 2 {
                    println!("    CA write 0x{:04X} ({}B) failed x3: {:?}", idx, blob.len(), e);
                    return false;
                }
                std::thread::sleep(Duration::from_millis(100));
            }
        }
    }
    false
}

async fn read_u8<S>(sd: &ethercrab::SubDeviceRef<'_, S>, idx: u16, sub: u8) -> u8
where
    S: std::ops::Deref<Target = ethercrab::SubDevice>,
{
    sd.sdo_read(idx, sub).await.unwrap_or(0xFF)
}

/// Raw AL control request + poll until the state takes effect (max ~3 s).
/// Returns (AL status, AL status code).
///
/// The AL control register is a *command* register: the protocol requires
/// writing the full target state, so read-modify-write does not apply.
pub async fn drive_state(md: &MainDevice<'_>, station: u16, state: u16) -> (u16, u16) {
    let _ = Command::fpwr(station, regs::AL_CONTROL).send(md, state).await;
    for _ in 0..20 {
        std::thread::sleep(Duration::from_millis(150));
        let al = Command::fprd(station, regs::AL_STATUS)
            .receive::<u16>(md)
            .await
            .unwrap_or(0xFFFF);
        if al & regs::AL_ERROR != 0 || al & regs::AL_STATE_MASK == state {
            let alc = Command::fprd(station, regs::AL_STATUS_CODE)
                .receive::<u16>(md)
                .await
                .unwrap_or(0xFFFF);
            return (al, alc);
        }
    }
    (0xFFFF, 0xFFFF)
}

pub fn verdict(al: u16, alc: u16) -> String {
    let state = match al & 0x0F {
        1 => "INIT",
        2 => "PREOP",
        4 => "SAFEOP",
        8 => "OP",
        _ => "?",
    };
    let meaning = match alc {
        0x0000 => "OK",
        0x001D => "invalid OUTPUT config",
        0x001E => "invalid INPUT config",
        0x0003 => "invalid device setup",
        _ => "?",
    };
    format!(
        "AL=0x{:04X} ({}{}) code=0x{:04X} {}",
        al,
        state,
        if al & 0x10 != 0 { "+ERR" } else { "" },
        alc,
        meaning
    )
}

/// Ensure the user OD holds the expected PDO layout; (re)configure if not.
///
/// `txpdo_first` is the first TxPDO in 0x1C13: 0x1A01 (diagnostic word,
/// plain mode) or 0x1A02 (22-byte SYNC timestamps, follow mode).
///
/// If the mailbox is dead (SAFEOP-nuked from a previous session) the bridge
/// is cycled INIT -> PREOP first.
pub async fn ensure_od<S>(
    sd: &ethercrab::SubDeviceRef<'_, S>,
    md: &MainDevice<'_>,
    station: u16,
    txpdo_first: u16,
) -> Result<(), String>
where
    S: std::ops::Deref<Target = ethercrab::SubDevice>,
{
    let configured = match sd.sdo_read::<u16>(0x1C13, 1).await {
        Ok(v) if v == txpdo_first => {
            let rb = (
                read_u8(sd, 0x1C12, 0).await,
                read_u8(sd, 0x1C13, 0).await,
                read_u8(sd, 0x1608, 0).await,
                read_u8(sd, 0x1A08, 0).await,
            );
            if rb == (1, 2, 35, 35) {
                println!(
                    "EL6695 OD already configured (0x1C13=[0x{:04X}, 0x1A08])",
                    txpdo_first
                );
                return Ok(());
            }
            println!("EL6695 OD partial (rb={:?}); rewriting layout...", rb);
            true
        }
        Ok(v) => {
            println!(
                "EL6695 OD has 0x1C13:01=0x{:04X}, need 0x{:04X}; reconfiguring...",
                v, txpdo_first
            );
            true
        }
        Err(e) => {
            println!("SDO read failed ({:?}); INIT->PREOP reset then configure", e);
            let (al, _) = drive_state(md, station, 0x0001).await;
            if al & 0x0F != 0x01 {
                return Err(format!("not INIT after reset ({})", verdict(al, 0)));
            }
            let (al, alc) = drive_state(md, station, 0x0002).await;
            if al & 0x0F != 0x02 {
                return Err(format!("not PREOP after reset ({})", verdict(al, alc)));
            }
            true
        }
    };

    if !configured {
        return Ok(());
    }

    let mut ok = true;
    ok &= sdo_ca(sd, 0x1608, &twin_layout_blob(0x7000)).await;
    ok &= sdo_ca(sd, 0x1A08, &twin_layout_blob(0x6000)).await;
    ok &= sdo_ca(sd, 0x1C12, &assign_blob(&[0x1608])).await;
    ok &= sdo_ca(sd, 0x1C13, &assign_blob(&[txpdo_first, 0x1A08])).await;
    let rb = (
        read_u8(sd, 0x1C12, 0).await,
        read_u8(sd, 0x1C13, 0).await,
        read_u8(sd, 0x1608, 0).await,
        read_u8(sd, 0x1A08, 0).await,
    );
    let a1 = sd.sdo_read::<u16>(0x1C13, 1).await.unwrap_or(0xFFFF);
    let a2 = sd.sdo_read::<u16>(0x1C13, 2).await.unwrap_or(0xFFFF);
    println!(
        "  writes_ok={} rb={:?} 0x1C13=[0x{:04X}, 0x{:04X}]",
        ok, rb, a1, a2
    );
    if !ok || rb != (1, 2, 35, 35) || (a1, a2) != (txpdo_first, 0x1A08) {
        return Err("PDO config write/readback mismatch".into());
    }
    Ok(())
}

/// Raw SM2/SM3 register config (start/len/ctrl/enable per the ESI).
///
/// Start/length/ctrl are complete configuration values written wholesale;
/// the enable byte is applied read-modify-write so unrelated bits survive.
pub async fn write_sms(md: &MainDevice<'_>, station: u16, sm2_addr: u16, sm2_len: u16, sm3_addr: u16, sm3_len: u16) {
    use crate::regs::*;
    // SM2: outputs (master -> slave), ESI ctrl byte
    let _ = Command::fpwr(station, sm_base(2) + SM_OFF_START).send(md, sm2_addr).await;
    let _ = Command::fpwr(station, sm_base(2) + SM_OFF_LEN).send(md, sm2_len).await;
    let _ = Command::fpwr(station, sm_base(2) + SM_OFF_CTRL).send(md, SM_CTRL_OUTPUTS_ESI).await;
    let _ = rmw_u8(md, station, sm_base(2) + SM_OFF_ENABLE, SM_ENABLE, 0).await;
    // SM3: inputs (slave -> master), ESI ctrl byte
    let _ = Command::fpwr(station, sm_base(3) + SM_OFF_START).send(md, sm3_addr).await;
    let _ = Command::fpwr(station, sm_base(3) + SM_OFF_LEN).send(md, sm3_len).await;
    let _ = Command::fpwr(station, sm_base(3) + SM_OFF_CTRL).send(md, SM_CTRL_INPUTS_ESI).await;
    let _ = rmw_u8(md, station, sm_base(3) + SM_OFF_ENABLE, SM_ENABLE, 0).await;
}