X-Git-Url: https://gerrit.automotivelinux.org/gerrit/gitweb?a=blobdiff_plain;f=README.md;h=29baa3a3bfbde99f1f472ba921c5c9f2a3abcbea;hb=fde9efb8224468dd8fb3c6204a7e80a9dd38a97c;hp=ba1641929e0047a0872bb460dc11a66c986a5d83;hpb=d5d62371b4b6b2c2c7211aef55a3a967540948fe;p=apps%2Fagl-service-can-low-level.git diff --git a/README.md b/README.md index ba164192..29baa3a3 100644 --- a/README.md +++ b/README.md @@ -1,126 +1,40 @@ # 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. - -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. - -## Diagnostic Messages - -### Requests - - {"bus": 1, - "id": 1234, - "mode": 1, - "pid": 5, - "payload": "0x1234", - "frequency": 0} +interfaces (e.g. USB or Bluetooth) as JSON or Protocol Buffers (protobuf). -**bus** - the numerical identifier of the CAN bus where this request should be - sent, most likely 1 or 2 (for a vehicle interface with 2 CAN controllers). +## JSON -**id** - the CAN arbitration ID for the request. +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. -**mode** - the OBD-II mode of the request - 0x1 through 0xf (0x1 through 0xa - are the standardized modes). +The JSON format is best for most developers, as it is fairly efficient and very +flexible. -**pid** - (optional) the PID for the request, if applicable. +## Binary (Protocol Buffers) -**payload** - (optional) up to 7 bytes of data for the request'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. +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. -**frequency** - (optional, defaults to 0) The frequency in Hz to send this - request. To send a single request, set this to 0 or leave it out. +The binary messages are published by the VI using the standard length-delimited +method (any protobuf library should support this). -TODO it'd be nice to have the OBD-II PIDs built in, with the proper conversion -functions - that may need a different output format - -If you're just requesting a PID, you can use a simplified format for the -request: - - {"bus": 1, "id": 1234, "mode": 1, "pid": 5} - -### Responses - - {"bus": 1, - "id": 1234, - "mode": 1, - "pid": 5, - "success": true, - "negative_response_code": 17, - "payload": "0x1234"} - -**bus** - the numerical identifier of the CAN bus where this response was - received. - -**id** - the CAN arbitration ID for this response. - -**mode** - the OBD-II mode of the original diagnostic request. - -**pid** - (optional) the PID for the request, if applicable. - -**success** - true if the response received was a positive response. If this - field is false, the remote node returned an error and the - `negative_response_code` field should be populated. - -**negative_response_code** - (optional) If requsted node returned an error, - `success` will be `false` and this field will contain the negative response - code (NRC). - -**payload** - (optional) up to 7 bytes of data returned in the response, - 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. - -The response to a simple PID requset would look like this: - - {"bus": 1, "id": 1234, "mode": 1, "pid": 5, "payload": "0x2"} - -TODO again, it'd be nice to have the OBD-II PIDs built in, with the proper -conversion functions so the response here included the actual transformed value -of the pid and a human readable name +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. ## Trace File Format An OpenXC vehicle trace file is a plaintext file that contains JSON objects, -separated by newlines. +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: @@ -177,11 +91,11 @@ 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 @@ -217,10 +131,31 @@ manufacturers may support custom message names. * 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) 2012-2013 Ford Motor Company +Copyright (c) 2012-2014 Ford Motor Company Licensed under the BSD license.