LDF Parser

Common errors

• FileNotFoundError: 'non_existent.ldf' doesn't exist

  cause The path provided to `ldfparser.parse_ldf` does not point to an accessible LDF file.
  fix Ensure the LDF file exists at the specified path and that the Python process has read permissions for it. Double-check the file name and directory.

• KeyError: 'Frame_X'

  cause Attempted to access a frame (e.g., `ldf.get_unconditional_frame('Frame_X')`) or signal that does not exist or is misspelled in the parsed LDF.
  fix Verify the exact name of the frame or signal in the LDF file. Use `ldf.frames` or `ldf.signals` to inspect available names or iterate through them.

• AttributeError: 'LinSignal' object has no attribute 'frame'

  cause Attempting to access `signal.frame` when the signal is associated with multiple frames, especially after v0.26.0 which introduced `signal.frames`.
  fix Use `signal.frames` (which is a list of frames) to determine the owners of a signal. Iterate over this list if a signal can belong to multiple frames. For signals with a single frame owner, `signal.frame` will still be populated for backward compatibility.

• ldfparser.parser.LDFParserException: Error parsing LDF file: ...

  cause The provided LDF file contains syntax errors or deviations from the LIN standard that the parser cannot handle, leading to a parsing failure.
  fix Review the LDF file for syntax errors. Validate it with a commercial LDF editor if possible. Consider simplifying the LDF to isolate the problematic section or upgrading `ldfparser` if it's an old version with a known parsing bug.

Warnings

• breaking As of v0.26.0, `signal.frames` is the new way to determine signal owners for compatibility with signals associated with multiple frames. While `signal.frame` is still set if a signal belongs to only one frame, relying on `signal.frame` directly for multi-frame signals is discouraged.
  Fix: Migrate code to use `signal.frames` (which returns a list) instead of `signal.frame` when iterating over signal ownership.
• breaking In v0.26.0, physical values are now rounded to the nearest integer during conversion, rather than always rounded down. This can change the output of decoded signals.
  Fix: Review any logic that depends on the previous rounding-down behavior for physical value conversions and adjust expectations or implement custom rounding if needed.
• deprecated Prior to v0.10.0, several functions like `parseLDF`, `parseLDFtoDict`, `parseComments`, and direct attribute access like `LDF.frame(x)` were common. These have been deprecated in favor of snake_case function names (`parse_ldf`) and proper getter methods.
  Fix: Update function calls to their snake_case equivalents (e.g., `parse_ldf`) and use getter methods (e.g., `ldf.get_frame('FrameName')`) to ensure future compatibility.
• gotcha The library is in a 'pre-release' state, and features may break between minor versions. This means APIs or internal behaviors can change without a major version increment.
  Fix: It is highly recommended to pin the exact minor version (e.g., `ldfparser==0.26.0`) in production environments and perform thorough integration tests when updating to a new minor version.
• gotcha Due to known ambiguities or errors in LIN standard documentation, `ldfparser` cannot guarantee parsing correctness for *all* LDF files.
  Fix: If parsing issues occur, first verify the LDF file with a commercial tool (e.g., Vector LDF Explorer). If the LDF is valid, consider opening an issue with an anonymized LDF snippet.

Install

• pip install ldfparser Install stable version

Imports

• parse_ldf

  from ldfparser import parse_ldf

  The primary function to load and parse an LDF file.
• LDF

  import ldfparser
  ldf = ldfparser.parse_ldf(path='file.ldf')

  The LDF object is returned by parse_ldf and provides access to parsed data.

Quickstart

This quickstart demonstrates how to parse an LDF file, retrieve network parameters like baudrate, access specific frames, and then encode and decode LIN messages using defined signals. A temporary LDF file is created for a runnable example.

import ldfparser
import os
import tempfile
import binascii

# Create a dummy LDF file for demonstration
ldf_content = """
LIN_description_file;
LIN_protocol_version = "2.1";
LIN_language_version = "2.1";
LIN_speed = 19.2 kbps;
Nodes {
    Master: MasterNode, 5 ms, 0.1 ms;
    Slaves: SlaveNode1;
}
Signals {
    EngineRPM: 12, 0, MasterNode, MasterNode;
    CoolantTemp: 8, 12, MasterNode, MasterNode;
}
Frames {
    EngineFrame: 0x10, 8, MasterNode;
    Signals {
        EngineRPM, 0;
        CoolantTemp, 2;
    }
}
Signal_encoding_types {
    MotorRPM_encoding:
        physical_value,
        0, 255, 1, 0, "RPM";
}
Signal_representation {
    MotorRPM_encoding: EngineRPM;
}
"""

with tempfile.NamedTemporaryFile(mode='w', delete=False, suffix='.ldf') as temp_ldf_file:
    temp_ldf_file.write(ldf_content)
    ldf_path = temp_ldf_file.name

try:
    # Load LDF
    ldf = ldfparser.parse_ldf(path=ldf_path)
    print(f"Successfully parsed LDF from: {ldf_path}")

    # Get baudrate
    print(f"Baudrate: {ldf.get_baudrate()} kbps")

    # Get an unconditional frame
    frame = ldf.get_unconditional_frame('EngineFrame')
    print(f"Frame 'EngineFrame' ID: {frame.frame_id}, Length: {frame.length} bytes")

    # Encode signal values
    signal_values = {"EngineRPM": 1500, "CoolantTemp": 95}
    message = frame.encode(signal_values)
    print(f"Encoded message for {signal_values}: 0x{binascii.hexlify(message).decode('utf-8')}")

    # Decode message
    decoded_values = frame.decode(message)
    print(f"Decoded message: {decoded_values}")

except Exception as e:
    print(f"An error occurred: {e}")
finally:
    # Clean up the temporary LDF file
    if os.path.exists(ldf_path):
        os.remove(ldf_path)