Luca
c32c4645b5
Tooling and findings for running an E8x/E9x electric power steering unit
outside its donor car, e.g. in an EV conversion.
Headline result: the EPS needs only two CAN messages plus a 12V enable
wire, not the 69-message set the car puts on the bus:
0x130 CAS terminal status (100ms) brings the unit up
0x1A0 DSC road speed (20ms) sets the assist level
Total required rate is 60 frames/s. Protocol write-up, including what is
proven vs. inferred and the open questions, is in eps-comms/.
Contents:
adapters/ CANdapter (its SLCAN dialect differs) and generic SLCAN
gateway/ car<->EPS relay, replay, message bench, EPS controller,
4-tab Streamlit UI
decoder/ PT-CAN frame decoding and live/replay sources
can-io/ XIAO ESP32-S3 firmware: CAN IO board + USB-CAN bridge with
a CAN-independent digital IO channel
tools/ capture, bitrate scan, startup-order and session analysis,
checksum solver
captures/ reference working session + the replay set eps_control reads
66 lines
2.4 KiB
Python
66 lines
2.4 KiB
Python
"""Read and decode CAN frames from the CANdapter (candapter.com) USB adapter.
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Usage:
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python read_can.py [--bitrate 500000] [--port /dev/cu.usbserial-DNBJV4F5]
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Connect the adapter to the CAN bus first, then run this script. It opens the
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channel at the given bitrate and prints every frame it receives: timestamp,
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arbitration ID (with an 'x' suffix for 29-bit extended IDs), DLC, raw bytes
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(hex), and an ASCII preview.
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If you don't know the bus's bitrate, common values are 125000, 250000,
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500000 (most likely - the adapter is rated for automotive use at 500 kbps),
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and 1000000. Wrong bitrate usually means zero frames or garbled data --
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try another value.
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"""
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import argparse
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import sys
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from pathlib import Path
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sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
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from adapters.candapter import Candapter # noqa: E402
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DEFAULT_PORT = "/dev/cu.usbserial-DNBJV4F5"
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DEFAULT_BITRATE = 500000
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def ascii_preview(data: bytes) -> str:
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return "".join(chr(b) if 32 <= b < 127 else "." for b in data)
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def main() -> int:
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parser = argparse.ArgumentParser(description=__doc__)
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parser.add_argument("--port", default=DEFAULT_PORT, help="Serial device path")
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parser.add_argument("--bitrate", type=int, default=DEFAULT_BITRATE, help="CAN bus bitrate")
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args = parser.parse_args()
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try:
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adapter = Candapter(args.port, args.bitrate, timestamps=True)
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except (OSError, ValueError) as exc:
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print(f"Failed to open adapter on {args.port}: {exc}", file=sys.stderr)
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return 1
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print(f"Listening on {args.port} at {args.bitrate} bps (Ctrl+C to stop)...\n")
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print(f"{'timestamp':>14} {'id':>10} {'dlc':>3} data (hex) ascii")
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try:
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with adapter:
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while True:
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frame = adapter.read_frame(timeout=None)
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if frame is None:
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continue
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id_str = f"{frame.arbitration_id:08X}x" if frame.is_extended else f"{frame.arbitration_id:03X}"
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data_hex = " ".join(f"{b:02X}" for b in frame.data)
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ts = frame.timestamp_ms if frame.timestamp_ms is not None else frame.recv_time
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print(
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f"{ts:14.3f} {id_str:>10} {len(frame.data):>3} "
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f"{data_hex:<24} {ascii_preview(frame.data)}"
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)
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except KeyboardInterrupt:
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print("\nStopped.")
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return 0
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if __name__ == "__main__":
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raise SystemExit(main())
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