1 # OpenXC Message Format Specification
3 This specification is a part of the [OpenXC platform][OpenXC].
5 An OpenXC vehicle interface sends generic vehicle data over one or more output
6 interfaces (e.g. USB or Bluetooth) as JSON objects, separated by newlines.
8 There are two valid message types - single valued and evented.
10 There may not be a 1:1 relationship between input and output signals - i.e. raw
11 engine timing CAN signals may be summarized in an "engine performance" metric on
12 the abstract side of the interface.
16 The expected format of a single valued message is:
18 {"name": "steering_wheel_angle", "value": 45}
22 The expected format of an event message is:
24 {"name": "button_event", "value": "up", "event": "pressed"}
26 This format is good for something like a button event, where there are two
27 discrete pieces of information in the measurement.
31 These signal names are a part of the OpenXC specification, although some
32 manufacturers may support custom message names.
34 * steering_wheel_angle
36 * torque_at_transmission
40 * vehicle_speed, numerical, Kph
41 * accelerator_pedal_position
43 * parking_brake_status
44 * boolean, (true == brake engaged)
46 * boolean (True == pedal pressed)
47 * transmission_gear_position
48 * states: first, second, third, fourth, fifth, sixth, seventh, eighth,
51 * states: neutral, park, reverse, drive, sport, low, first, second, third,
56 * states: off, accessory, run, start
59 * fuel_consumed_since_restart
60 * numerical, liters (goes to 0 every time the
61 vehicle interfaces power cycles)
63 * Value is State: driver, passenger, rear_left, rear_right.
64 * Event is boolean: true == ajar
69 * windshield_wiper_status
76 ## Raw CAN Message format
78 An OpenXC vehicle interface may also output raw CAN messages. Each CAN message
79 is sent as a JSON object, separated by newlines. The format of each object is:
81 {"bus": 1, "id": 1234, "value": "0x12345678"}
83 **bus** - the numerical identifier of the CAN bus where this message originated,
84 most likely 1 or 2 (for a vehicle interface with 2 CAN controllers).
86 **id** - the CAN message ID
88 **data** - up to 8 bytes of data from the CAN message's payload, represented as
89 a hexidecimal number in a string. Many JSON parser cannot handle 64-bit
90 integers, which is why we are not using a numerical data type.
95 Copyright (c) 2012-2013 Ford Motor Company
97 Licensed under the BSD license.
99 [OpenXC]: http://openxcplatform.com