This specification is a part of the OpenXC platform.

An OpenXC vehicle interface sends generic vehicle data over one or more output interfaces (e.g. USB or Bluetooth) as JSON objects, separated by newlines.

There are two valid message types - single valued and evented.

There may not be a 1:1 relationship between input and output signals - i.e. raw engine timing CAN signals may be summarized in an "engine performance" metric on the abstract side of the interface.

The expected format of a single valued message is:

{"name": "steering_wheel_angle", "value": 45}

The expected format of an event message is:

{"name": "button_event", "value": "up", "event": "pressed"}

This format is good for something like a button event, where there are two discrete pieces of information in the measurement.

An OpenXC vehicle interface may also output raw CAN messages. Each CAN message is sent as a JSON object, separated by newlines. The format of each object is:

{"bus": 1, "id": 1234, "value": "0x12345678"}

bus - the numerical identifier of the CAN bus where this message originated, most likely 1 or 2 (for a vehicle interface with 2 CAN controllers).

id - the CAN message ID

data - up to 8 bytes of data from the CAN message's payload, represented as a hexidecimal number in a string. Many JSON parser cannot handle 64-bit integers, which is why we are not using a numerical data type.

An OpenXC vehicle trace file is a plaintext file that contains JSON objects, separated by newlines.

The first line may be a metadata object, although this is optional:

{"metadata": {
    "version": "v3.0",
    "vehicle_interface_id": "7ABF",
    "vehicle": {
        "make": "Ford",
        "model": "Mustang",
        "trim": "V6 Premium",
        "year": 2013
    },
    "description": "highway drive to work",
    "driver_name": "TJ Giuli",
    "vehicle_id": "17N1039247929"
}

The following lines are OpenXC messages with a timestamp field added, e.g.:

{"timestamp": 1385133351.285525, "name": "steering_wheel_angle", "value": 45}

The timestamp is in UNIX time (i.e. seconds since the UNIX epoch, 00:00:00 UTC, 1/1/1970).

These signal names are a part of the OpenXC specification, although some manufacturers may support custom message names.

• steering_wheel_angle
  • numerical, -600 to +600 degrees
  • 10Hz
• torque_at_transmission
  • numerical, -500 to 1500 Nm
  • 10Hz
• engine_speed
  • numerical, 0 to 16382 RPM
  • 10Hz
• vehicle_speed
  • numerical, 0 to 655 km/h (this will be positive even if going in reverse as it's not a velocity, although you can use the gear status to figure out direction)
  • 10Hz
• accelerator_pedal_position
  • percentage
  • 10Hz
• parking_brake_status
  • boolean, (true == brake engaged)
  • 1Hz, but sent immediately on change
• brake_pedal_status
  • boolean (True == pedal pressed)
  • 1Hz, but sent immediately on change
• transmission_gear_position
  • states: first, second, third, fourth, fifth, sixth, seventh, eighth, reverse, neutral
  • 1Hz, but sent immediately on change
• gear_lever_position
  • states: neutral, park, reverse, drive, sport, low, first, second, third, fourth, fifth, sixth
  • 1Hz, but sent immediately on change
• odometer
  • Numerical, km 0 to 16777214.000 km, with about .2m resolution
  • 10Hz
• ignition_status
  • states: off, accessory, run, start
  • 1Hz, but sent immediately on change
• fuel_level
  • percentage
  • 2Hz
• fuel_consumed_since_restart
  • numerical, 0 - 4294967295.0 L (this goes to 0 every time the vehicle restarts, like a trip meter)
  • 10Hz
• door_status
  • Value is State: driver, passenger, rear_left, rear_right.
  • Event is boolean: true == ajar
  • 1Hz, but sent immediately on change
• headlamp_status
  • boolean, true is on
  • 1Hz, but sent immediately on change
• high_beam_status
  • boolean, true is on
  • 1Hz, but sent immediately on change
• windshield_wiper_status
  • boolean, true is on
  • 1Hz, but sent immediately on change
• latitude
  • numerical, -89.0 to 89.0 degrees with standard GPS accuracy
  • 1Hz
• longitude
  • numerical, -179.0 to 179.0 degrees with standard GPS accuracy
  • 1Hz

Copyright (c) 2012-2013 Ford Motor Company

Licensed under the BSD license.