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diff --git a/libs/openxc-message-format/README.md b/libs/openxc-message-format/README.md new file mode 100644 index 00000000..77758b83 --- /dev/null +++ b/libs/openxc-message-format/README.md @@ -0,0 +1,177 @@ +# 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 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. + +## 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 + +For protocol specification visit: +https://github.com/msgpack/msgpack/blob/master/spec.md + +We are using the following lib: +https://github.com/camgunz/cmp + +MessagePack provides a binary alternative to ProtoBuf. There are pros & cons to each +so you can decide what works best for your project. + +## Trace File Format + +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 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 + +## Signals from Diagnostic Messages + +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). + +* 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) 2012-2014 Ford Motor Company + +Licensed under the BSD license. + +[OpenXC]: http://openxcplatform.com |