X-Git-Url: https://gerrit.automotivelinux.org/gerrit/gitweb?a=blobdiff_plain;f=README.md;h=77758b835865fd28d1c877de832125aba5ff7bcb;hb=15cd69864383276e2099b803cdb11cda7f2f6d0a;hp=30720db54e04d9f044143ea44671027659d03d88;hpb=2e14ec89c5fb2e3c0d4ed4bcde5e7b04443f0413;p=apps%2Flow-level-can-service.git diff --git a/README.md b/README.md index 30720db..77758b8 100644 --- a/README.md +++ b/README.md @@ -1,30 +1,80 @@ # OpenXC Message Format Specification +Version: v0.6.0 + 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. + +The binary messages are published by the VI using the standard length-delimited +method (any protobuf library should support this). + +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. -There are two valid message types - single valued and evented. +## Message Pack +MessagePack is an efficient binary serialization format. It lets you exchange data +among multiple languages like JSON, but it's faster and smaller. Small integers are +encoded into a single byte, and typical short strings require only one extra byte +in addition to the strings themselves -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. +For protocol specification visit: +https://github.com/msgpack/msgpack/blob/master/spec.md -## Single Valued +We are using the following lib: +https://github.com/camgunz/cmp -The expected format of a single valued message is: +MessagePack provides a binary alternative to ProtoBuf. There are pros & cons to each +so you can decide what works best for your project. - {"name": "steering_wheel_angle", "value": 45} +## Trace File Format -## Evented +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). -The expected format of an event message is: +The first line may be a metadata object, although this is optional: - {"name": "button_event", "value": "up", "event": "pressed"} +``` +{"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" +} +``` -This format is good for something like a button event, where there are two -discrete pieces of information in the measurement. +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 @@ -56,11 +106,11 @@ manufacturers may support custom message names. * 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 @@ -96,26 +146,31 @@ manufacturers may support custom message names. * numerical, -179.0 to 179.0 degrees with standard GPS accuracy * 1Hz -## 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"} +## Signals from Diagnostic Messages -**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). +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). -**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.