# OpenXC Message Format Specification
+Version: v0.4-dev
+
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.
+interfaces (e.g. USB or Bluetooth) as JSON or Protocol Buffers (protobuf).
+
+## JSON
+
+The JSON format is the most flexible and easiest to use. The format is fully
+specified in the [JSON.mkd](JSON.mkd) file in this repository.
+a more flexible option than binary, but is less compact and
+therefore takes more bandwidth and processing power.
+
+The JSON format is best for most developers, as it is fairly efficient and very
+flexible.
+
+## Binary (Protocol Buffers)
+
+The binary format is encoded using [Google Protocol
+Buffers](https://code.google.com/p/protobuf/). The format is specified in the
+file [openxc.proto](openxc.proto). The descriptions of the messages can be foud
+in the JSON specs - the binary format mirrors this.
-There are two valid message types - single valued and evented.
+The binary messages are published by the VI using the standard length-delimited
+method (any protobuf library should support this).
-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 binary format is best if you need to maximize the amount of data that can be
+sent from the VI, trading off flexibility for efficiency.
-## Single Valued
+## Trace File Format
-The expected format of a single valued message is:
+An OpenXC vehicle trace file is a plaintext file that contains JSON objects,
+separated by newlines (which may be either `\r\n` or `\n`, depending on the
+platform the trace file was recorded).
- {"name": "steering_wheel_angle", "value": 45}
+The first line may be a metadata object, although this is optional:
-## Evented
+```
+{"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 expected format of an event message is:
+The following lines are OpenXC messages with a `timestamp` field added, e.g.:
- {"name": "button_event", "value": "up", "event": "pressed"}
+ {"timestamp": 1385133351.285525, "name": "steering_wheel_angle", "value": 45}
-This format is good for something like a button event, where there are two
-discrete pieces of information in the measurement.
+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
* 1Hz, but sent immediately on change
* transmission_gear_position
* states: first, second, third, fourth, fifth, sixth, seventh, eighth,
- reverse, neutral
+ 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
+ fourth, fifth, sixth, seventh, eighth, ninth, tenth
* 1Hz, but sent immediately on change
* odometer
* Numerical, km
* numerical, -179.0 to 179.0 degrees with standard GPS accuracy
* 1Hz
-## Raw CAN Message format
+## Signals from Diagnostic Messages
-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:
+This set of signals is often retreived from OBD-II requests. The units can be
+found in the [OBD-II standard](http://en.wikipedia.org/wiki/OBD-II_PIDs#Mode_01).
- {"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.
+* engine_load
+* engine_coolant_temperature
+* barometric_pressure
+* commanded_throttle_position
+* throttle_position
+* fuel_level
+* intake_air_temperature
+* intake_manifold_pressure
+* running_time
+* fuel_pressure
+* mass_airflow
+* accelerator_pedal_position
+* ethanol_fuel_percentage
+* engine_oil_temperature
+* engine_torque
License
=======
-Copyright (c) 2012-2013 Ford Motor Company
+Copyright (c) 2012-2014 Ford Motor Company
Licensed under the BSD license.
Code Review / apps / agl-service-can-low-level.git / blobdiff