90 lines
4.4 KiB
Markdown
90 lines
4.4 KiB
Markdown
# LIN Interface Call Flow
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This document explains how LIN operations flow through the abstraction for the Mock, MUM, and legacy BabyLIN adapters.
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## Contract (base)
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File: `ecu_framework/lin/base.py`
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- `connect()` / `disconnect()`
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- `send(frame: LinFrame)`
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- `receive(id: int | None = None, timeout: float = 1.0) -> LinFrame | None`
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- `request(id: int, length: int, timeout: float = 1.0) -> LinFrame | None`
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- `flush()`
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`LinFrame` validates:
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- ID is 0x00–0x3F (6-bit LIN ID)
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- Data length ≤ 8 bytes
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## Mock adapter flow
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File: `ecu_framework/lin/mock.py`
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- `connect()`: initialize buffers and state
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- `send(frame)`: enqueues the frame and (for echo behavior) schedules it for RX
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- `receive(timeout)`: waits up to timeout for a frame in RX buffer
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- `request(id, length, timeout)`: synthesizes a deterministic response of the given length for predictability
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- `disconnect()`: clears state
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Use cases:
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- Fast local dev, deterministic responses, no hardware
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- Timeout and boundary behavior validation
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## MUM adapter flow (Melexis Universal Master)
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File: `ecu_framework/lin/mum.py`
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The MUM is a networked LIN master (default IP `192.168.7.2`) with built-in
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power control on `power_out0`. It is **master-driven**: there is no passive
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listen — to read a slave-published frame, the master triggers a header on
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that frame ID. Diagnostic frames (BSM-SNPD, service ID 0xB5) require LIN 1.x
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**Classic** checksum and are sent through the transport layer's
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`ld_put_raw`, not the regular `send_message`.
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- `connect()`: lazy-imports `pymumclient` + `pylin`; opens MUM
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(`MelexisUniversalMaster.open_all(host)`), gets the LIN device
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(`linmaster`) and power device (`power_control`), runs `linmaster.setup()`,
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builds `LinBusManager` + `LinDevice22`, sets `lin_dev.baudrate`, fetches
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the transport layer (`get_device("bus/transport_layer")`), and finally
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`power_control.power_up()` followed by a `boot_settle_seconds` sleep
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- `send(frame)`: `lin_dev.send_message(master_to_slave=True, frame_id, data_length, data)`
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- `receive(id, timeout)`: `lin_dev.send_message(master_to_slave=False, frame_id=id, data_length=frame_lengths.get(id, default_data_length))`
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— pylin returns the response bytes (or raises on timeout, which we treat as `None`).
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`id=None` raises `NotImplementedError` because the MUM cannot listen passively.
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- `disconnect()`: best-effort `power_control.power_down()` followed by `linmaster.teardown()`
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- MUM-only extras: `send_raw(bytes)` (Classic checksum via `ld_put_raw`),
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`power_up()`, `power_down()`, `power_cycle(wait)`
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Configuration:
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- `interface.host` is required; `interface.lin_device` and `interface.power_device` default to MUM conventions
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- `interface.bitrate` is the actual LIN baudrate the MUM drives
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- `interface.frame_lengths` lets you map slave frame IDs to their fixed data lengths so `receive(id)` can fetch the correct number of bytes; built-in defaults cover ALM_Status (4) and ALM_Req_A (8)
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## BabyLIN adapter flow (SDK wrapper)
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File: `ecu_framework/lin/babylin.py`
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- `connect()`: import SDK `BabyLIN_library.py`, discover ports, open first, optionally `BLC_loadSDF`, get channel handle, and `BLC_sendCommand("start schedule N;")`
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- `send(frame)`: calls `BLC_mon_set_xmit(channelHandle, frameId, data, slotTime=0)`
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- `receive(timeout)`: calls `BLC_getNextFrameTimeout(channelHandle, timeout_ms)` and converts returned `BLC_FRAME` to `LinFrame`
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- `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()`
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- `disconnect()`: calls `BLC_closeAll()`
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- Error handling: uses `BLC_getDetailedErrorString` (if available)
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Configuration:
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- `interface.sdf_path` locates the SDF to load
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- `interface.schedule_nr` sets the schedule to start upon connect
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- `interface.channel` selects the channel index
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## Edge considerations
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- Ensure the correct architecture (x86/x64) of the DLL matches Python
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- Channel/bitrate must match your network configuration
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- Some SDKs require initialization/scheduling steps before transmit/receive
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- Time synchronization and timestamp units vary per SDK — convert as needed
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Note on master requests:
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- Our mock wrapper returns a deterministic byte pattern when called with the `length` signature.
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- When only the bytes signature is available, zeros of the requested length are used in tests.
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