ecu-tests/docs/04_lin_interface_call_flow.md

LIN Interface Call Flow

This document explains how LIN operations flow through the abstraction for both Mock and BabyLin adapters.

Contract (base)

File: ecu_framework/lin/base.py

• connect() / disconnect()
• send(frame: LinFrame)
• receive(id: int | None = None, timeout: float = 1.0) -> LinFrame | None
• request(id: int, length: int, timeout: float = 1.0) -> LinFrame | None
• flush()

LinFrame validates:

• ID is 0x00–0x3F (6-bit LIN ID)
• Data length ≤ 8 bytes

Mock adapter flow

File: ecu_framework/lin/mock.py

• connect(): initialize buffers and state
• send(frame): enqueues the frame and (for echo behavior) schedules it for RX
• receive(timeout): waits up to timeout for a frame in RX buffer
• request(id, length, timeout): synthesizes a deterministic response of the given length for predictability
• disconnect(): clears state

Use cases:

• Fast local dev, deterministic responses, no hardware
• Timeout and boundary behavior validation

BabyLIN adapter flow (SDK wrapper)

File: ecu_framework/lin/babylin.py

• connect(): import SDK BabyLIN_library.py, discover ports, open first, optionally BLC_loadSDF, get channel handle, and BLC_sendCommand("start schedule N;")
• send(frame): calls BLC_mon_set_xmit(channelHandle, frameId, data, slotTime=0)
• receive(timeout): calls BLC_getNextFrameTimeout(channelHandle, timeout_ms) and converts returned BLC_FRAME to LinFrame
• request(id, length, timeout): prefers BLC_sendRawMasterRequest(channel, id, length); falls back to (channel, id, bytes); if unavailable, sends a header and waits on receive()
• disconnect(): calls BLC_closeAll()
• Error handling: uses BLC_getDetailedErrorString (if available)

Configuration:

• interface.sdf_path locates the SDF to load
• interface.schedule_nr sets the schedule to start upon connect
• interface.channel selects the channel index

Edge considerations

• Ensure the correct architecture (x86/x64) of the DLL matches Python
• Channel/bitrate must match your network configuration
• Some SDKs require initialization/scheduling steps before transmit/receive
• Time synchronization and timestamp units vary per SDK — convert as needed

Note on master requests:

• Our mock wrapper returns a deterministic byte pattern when called with the length signature.
• When only the bytes signature is available, zeros of the requested length are used in tests.