Skip to content

Run and analyze a simulated vehicle traffic profile

Goal

Generate a believable mix of classic CAN frames, J1939 PGN traffic, and occasional DM1 fault bursts — without a live vehicle, a recorded capture, or any hardware — and then analyze the result with CANarchy's existing decode and DM1 tooling.

Step 1 — Plan a run with --dry-run

Before transmitting anything, inspect what a profile produces. --dry-run samples the same deterministic frame sequence but skips opening a transport:

canarchy simulate --profile heavy-truck --rate 50 --duration 2 --seed 1 --dry-run --text

command: simulate
interface: unknown
profile: heavy-truck
frames: 100
(0.000000) can0 0CF00400#1C2E2BB8569D806C
(0.020000) can0 18FEF200#0001020304050607
...

--seed makes the run reproducible: the same profile, rate, duration, and seed always produce the same arbitration IDs, payload bytes, and timestamps.

Step 2 — Pipe simulated traffic onto a virtual bus

Bring up a virtual SocketCAN interface (see Build a virtual CAN loop), then transmit the profile:

sudo modprobe vcan
sudo ip link add dev vcan0 type vcan
sudo ip link set up vcan0

canarchy simulate vcan0 --profile heavy-truck --rate 50 --duration 10 --seed 1 --ack-active

simulate is an active-transmit command: it prints a preflight warning, and with --ack-active it asks you to type YES before any frame leaves the interface — the same safety gate used by generate and send. You can also target a udp_multicast address or rely on --dry-run plus shell piping if you only need a candump-style stream for another tool.

Step 3 — Capture and decode the simulated traffic

In a second terminal, capture what the simulator produced:

canarchy capture vcan0 --candump > /tmp/heavy-truck-sim.candump

Then run it through the J1939 tooling exactly as you would a real capture — for example, to see the simulated DM1 fault burst:

canarchy j1939 dm1 /tmp/heavy-truck-sim.candump --json

The heavy-truck profile injects an SPN 110 (Engine Coolant Temperature) fault with FMI 16 and an amber warning lamp; passenger-car injects an SPN 84 (Vehicle Speed) fault with FMI 2 and the MIL lamp. Both decode cleanly because simulate packs DM1 payloads using the same byte layout canarchy.j1939.dm1_messages expects.

Step 4 — Add your own profile

Profiles are plain JSON resources under canarchy/resources/simulate/profiles.json — no code changes required. Each profile mixes weighted classic_frames, j1939_messages, and an optional dm1 burst:

{
  "my-archetype": {
    "description": "...",
    "classic_frames": [
      {"name": "...", "arbitration_id": "0x100", "extended": false, "dlc": 8, "weight": 4, "data_pattern": "counter"}
    ],
    "j1939_messages": [
      {"name": "EEC1", "pgn": 61444, "priority": 3, "source_address": 0, "dlc": 8, "weight": 8, "data_pattern": "counter"}
    ],
    "dm1": {
      "weight": 1,
      "source_address": 0,
      "lamp_status": "mil",
      "fault_codes": [{"spn": 110, "fmi": 16, "occurrence_count": 1}]
    }
  }
}

weight controls how often a template is sampled relative to its peers, and data_pattern may be counter, slow-drift, or random.

Where to go next