1 # OpenXC Message Format Specification
5 This specification is a part of the [OpenXC platform][OpenXC].
7 An OpenXC vehicle interface sends generic vehicle data over one or more output
8 interfaces (e.g. USB or Bluetooth) as JSON or Protocol Buffers (protobuf).
12 The JSON format is the most flexible and easiest to use. The format is fully
13 specified in the [JSON.mkd](JSON.mkd) file in this repository.
14 a more flexible option than binary, but is less compact and
15 therefore takes more bandwidth and processing power.
17 The JSON format is best for most developers, as it is fairly efficient and very
20 ## Binary (Protocol Buffers)
22 The binary format is encoded using [Google Protocol
23 Buffers](https://code.google.com/p/protobuf/). The format is specified in the
24 file [openxc.proto](openxc.proto). The descriptions of the messages can be foud
25 in the JSON specs - the binary format mirrors this.
27 The binary messages are published by the VI using the standard length-delimited
28 method (any protobuf library should support this).
30 The binary format is best if you need to maximize the amount of data that can be
31 sent from the VI, trading off flexibility for efficiency.
35 An OpenXC vehicle trace file is a plaintext file that contains JSON objects,
36 separated by newlines (which may be either `\r\n` or `\n`, depending on the
37 platform the trace file was recorded).
39 The first line may be a metadata object, although this is optional:
44 "vehicle_interface_id": "7ABF",
51 "description": "highway drive to work",
52 "driver_name": "TJ Giuli",
53 "vehicle_id": "17N1039247929"
57 The following lines are OpenXC messages with a `timestamp` field added, e.g.:
59 {"timestamp": 1385133351.285525, "name": "steering_wheel_angle", "value": 45}
61 The timestamp is in [UNIX time](http://en.wikipedia.org/wiki/Unix_time)
62 (i.e. seconds since the UNIX epoch, 00:00:00 UTC, 1/1/1970).
66 These signal names are a part of the OpenXC specification, although some
67 manufacturers may support custom message names.
69 * steering_wheel_angle
70 * numerical, -600 to +600 degrees
72 * torque_at_transmission
73 * numerical, -500 to 1500 Nm
76 * numerical, 0 to 16382 RPM
79 * numerical, 0 to 655 km/h (this will be positive even if going in reverse
80 as it's not a velocity, although you can use the gear status to figure out
83 * accelerator_pedal_position
86 * parking_brake_status
87 * boolean, (true == brake engaged)
88 * 1Hz, but sent immediately on change
90 * boolean (True == pedal pressed)
91 * 1Hz, but sent immediately on change
92 * transmission_gear_position
93 * states: first, second, third, fourth, fifth, sixth, seventh, eighth,
94 ninth, tenth, reverse, neutral
95 * 1Hz, but sent immediately on change
97 * states: neutral, park, reverse, drive, sport, low, first, second, third,
98 fourth, fifth, sixth, seventh, eighth, ninth, tenth
99 * 1Hz, but sent immediately on change
102 0 to 16777214.000 km, with about .2m resolution
105 * states: off, accessory, run, start
106 * 1Hz, but sent immediately on change
110 * fuel_consumed_since_restart
111 * numerical, 0 - 4294967295.0 L (this goes to 0 every time the vehicle
112 restarts, like a trip meter)
115 * Value is State: driver, passenger, rear_left, rear_right.
116 * Event is boolean: true == ajar
117 * 1Hz, but sent immediately on change
119 * boolean, true is on
120 * 1Hz, but sent immediately on change
122 * boolean, true is on
123 * 1Hz, but sent immediately on change
124 * windshield_wiper_status
125 * boolean, true is on
126 * 1Hz, but sent immediately on change
128 * numerical, -89.0 to 89.0 degrees with standard GPS accuracy
131 * numerical, -179.0 to 179.0 degrees with standard GPS accuracy
134 ## Signals from Diagnostic Messages
136 This set of signals is often retreived from OBD-II requests. The units can be
137 found in the [OBD-II standard](http://en.wikipedia.org/wiki/OBD-II_PIDs#Mode_01).
140 * engine_coolant_temperature
141 * barometric_pressure
142 * commanded_throttle_position
145 * intake_air_temperature
146 * intake_manifold_pressure
150 * accelerator_pedal_position
151 * ethanol_fuel_percentage
152 * engine_oil_temperature
158 Copyright (c) 2012-2014 Ford Motor Company
160 Licensed under the BSD license.
162 [OpenXC]: http://openxcplatform.com