trainsim/spec/interface.md

ATO ↔ TrainSim interface (v1)

Standalone. No ETCS. No ATP. JSON over HTTP.

Base URL (TrainSim): http://trainsim:8080

TrainSim → ATO reads

GET /train/state

{
  "speed_mps": 0.0,
  "position_m": 0.0,
  "track_length_m": 1000.0,
  "sim_running": false
}

ATO → TrainSim writes

POST /train/actuate

{
  "traction_pct": 0,
  "brake_pct": 0
}

Percent 0–100. Do not send both > 0 (TrainSim clamps brake wins).

POST /sim/start — start physics tick (empty body)

POST /sim/stop — pause physics (empty body)

Optional (TrainSim logs only): POST /train/doors { "command": "open" | "close" }

ATO configuration (env)

Variable	Meaning
TRAINSIM_URL	TrainSim base URL
TARGET_SPEED_MPS	Cruise target (default 10)
TICK_MS	Control period (default 100)