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# OpenXC Message Format Specification
This specification is a part of the [OpenXC platform][OpenXC].
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.
## Single Valued
The expected format of a single valued message is:
{"name": "steering_wheel_angle", "value": 45}
## Evented
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.
## Raw CAN Message format
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.
## Trace File Format
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](http://en.wikipedia.org/wiki/Unix_time)
(i.e. seconds since the UNIX epoch, 00:00:00 UTC, 1/1/1970).
## Official Signals
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,
ninth, tenth, reverse, neutral
* 1Hz, but sent immediately on change
* gear_lever_position
* states: neutral, park, reverse, drive, sport, low, first, second, third,
fourth, fifth, sixth, seventh, eighth, ninth, tenth
* 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
License
=======
Copyright (c) 2012-2013 Ford Motor Company
Licensed under the BSD license.
[OpenXC]: http://openxcplatform.com
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