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.
29 ## Raw CAN Message format
31 An OpenXC vehicle interface may also output raw CAN messages. Each CAN message
32 is sent as a JSON object, separated by newlines. The format of each object is:
34 {"bus": 1, "id": 1234, "value": "0x12345678"}
36 **bus** - the numerical identifier of the CAN bus where this message originated,
37 most likely 1 or 2 (for a vehicle interface with 2 CAN controllers).
39 **id** - the CAN message ID
41 **data** - up to 8 bytes of data from the CAN message's payload, represented as
42 a hexidecimal number in a string. Many JSON parser cannot handle 64-bit
43 integers, which is why we are not using a numerical data type.
47 An OpenXC vehicle trace file is a plaintext file that contains JSON objects,
48 separated by newlines.
50 The first line may be a metadata object, although this is optional:
55 "vehicle_interface_id": "7ABF",
62 "description": "highway drive to work",
63 "driver_name": "TJ Giuli",
64 "vehicle_id": "17N1039247929"
68 The following lines are OpenXC messages with a `timestamp` field added, e.g.:
70 {"timestamp": 1385133351.285525, "name": "steering_wheel_angle", "value": 45}
72 The timestamp is in [UNIX time](http://en.wikipedia.org/wiki/Unix_time)
73 (i.e. seconds since the UNIX epoch, 00:00:00 UTC, 1/1/1970).
77 These signal names are a part of the OpenXC specification, although some
78 manufacturers may support custom message names.
80 * steering_wheel_angle
81 * numerical, -600 to +600 degrees
83 * torque_at_transmission
84 * numerical, -500 to 1500 Nm
87 * numerical, 0 to 16382 RPM
90 * numerical, 0 to 655 km/h (this will be positive even if going in reverse
91 as it's not a velocity, although you can use the gear status to figure out
94 * accelerator_pedal_position
97 * parking_brake_status
98 * boolean, (true == brake engaged)
99 * 1Hz, but sent immediately on change
101 * boolean (True == pedal pressed)
102 * 1Hz, but sent immediately on change
103 * transmission_gear_position
104 * states: first, second, third, fourth, fifth, sixth, seventh, eighth,
106 * 1Hz, but sent immediately on change
107 * gear_lever_position
108 * states: neutral, park, reverse, drive, sport, low, first, second, third,
110 * 1Hz, but sent immediately on change
113 0 to 16777214.000 km, with about .2m resolution
116 * states: off, accessory, run, start
117 * 1Hz, but sent immediately on change
121 * fuel_consumed_since_restart
122 * numerical, 0 - 4294967295.0 L (this goes to 0 every time the vehicle
123 restarts, like a trip meter)
126 * Value is State: driver, passenger, rear_left, rear_right.
127 * Event is boolean: true == ajar
128 * 1Hz, but sent immediately on change
130 * boolean, true is on
131 * 1Hz, but sent immediately on change
133 * boolean, true is on
134 * 1Hz, but sent immediately on change
135 * windshield_wiper_status
136 * boolean, true is on
137 * 1Hz, but sent immediately on change
139 * numerical, -89.0 to 89.0 degrees with standard GPS accuracy
142 * numerical, -179.0 to 179.0 degrees with standard GPS accuracy
148 Copyright (c) 2012-2013 Ford Motor Company
150 Licensed under the BSD license.
152 [OpenXC]: http://openxcplatform.com