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
52 lines
1.7 KiB
Python
52 lines
1.7 KiB
Python
"""Probe the USB-CAN adapter to confirm it speaks a Lawicel-style ASCII protocol.
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The adapter is a CANdapter (Ewert Energy Systems / candapter.com), which
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enumerates as an FTDI FT240X USB-serial chip and shares its bring-up commands
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(V/N/S/O/C) with SLCAN, though its frame format diverges - see candapter.py.
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This script only exercises the shared commands (no CAN bus needs to be
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connected yet) to read the firmware version and serial number.
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"""
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import sys
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import time
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import serial
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PORT = "/dev/cu.usbserial-DNBJV4F5"
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BAUD = 115200 # standard SLCAN control baud rate (independent of CAN bitrate)
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def query(ser: serial.Serial, cmd: str, wait: float = 0.3) -> str:
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ser.reset_input_buffer()
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ser.write((cmd + "\r").encode("ascii"))
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time.sleep(wait)
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return ser.read(ser.in_waiting or 1).decode("ascii", errors="replace")
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def main() -> int:
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try:
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ser = serial.Serial(PORT, BAUD, timeout=1)
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except serial.SerialException as exc:
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print(f"Could not open {PORT}: {exc}", file=sys.stderr)
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return 1
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with ser:
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# Close channel first in case it was left open, ignore any response.
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query(ser, "C")
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version = query(ser, "V")
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serial_no = query(ser, "N")
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print(f"Port: {PORT}")
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print(f"Raw version reply: {version!r}")
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print(f"Raw serial# reply: {serial_no!r}")
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if version.startswith("V") or serial_no.startswith("N"):
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print("\nAdapter responded to SLCAN commands - looks like a Lawicel/CANUSB-compatible device.")
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else:
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print("\nNo recognizable SLCAN response. The adapter may use a different protocol.")
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return 0
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if __name__ == "__main__":
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raise SystemExit(main())
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