# 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).
+
+## 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`. Those are published 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.
+
+## JSON
+
+This document describes the JSON format and includes a high level description of
+each type and field. Each JSON message published by a VI is delimited with a
+`\0 ` character.
-There are two valid message types - single valued and evented.
+The JSON format is best for most developers, as it is fairly efficient and very
+flexible.
+
+### Extra Values
+
+Any of the following JSON objects may optionally include an `extras`
+field. The value may be any valid JSON object or array. The client libraries
+will do their best to parse this information into a generic format and pass it
+to your application. For example:
+
+ {"name": "steering_wheel_angle",
+ "value": 45,
+ "extras": {
+ "calibrated": false
+ }
+ }
+
+### Single Valued
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
+### Evented
The expected format of an event message is:
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
+
+The format for a raw CAN message:
+
+ {"bus": 1, "id": 1234, "data": "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. Each byte in
+ the string *must* be represented with 2 characters, e.g. `0x1` is `0x01` - the
+ complete string must have an even number of characters. The `0x` prefix is
+ optional.
+
+### Diagnostic Messages
+
+#### Requests
+
+A diagnostic request is added or cancelled with a JSON object like this example:
+
+ { "command": "diagnostic_request",
+ "action": "add",
+ "request": {
+ "bus": 1,
+ "id": 1234,
+ "mode": 1,
+ "pid": 5,
+ "payload": "0x1234",
+ "multiple_responses": false,
+ "frequency": 1,
+ "name": "my_pid"
+ }
+ }
+ }
+
+* The `command` must be `diagnostic_request.`
+* The `action` must be included, and must be one of:
+ * `add` - create a new one-off or recurring diagnostic request.
+ * `cancel` - cancel an existing request.
+* The details of the request must be included in the `request` field, using
+ the sub-fields defined below.
+
+A diagnostic request's `bus`, `id`, `mode` and `pid` (or lack of a `pid`)
+combine to create a unique key to identify a request. These four fields will be
+referred to as the key of the diagnostic request. For example, to create a
+simple one-time diagnostic request:
+
+ { "command": "diagnostic_request",
+ "action": "add",
+ "request": {
+ "bus": 1,
+ "id": 1234,
+ "mode": 1,
+ "pid": 5
+ }
+ }
+ }
+
+Requests are completed after any responses are received (unless
+`multiple_responses` is set), or the request has timed out after a certain
+number of seconds. After a request is completed, you can re-`create` the same
+key to make another request.
+
+Requests with a `frequency` are added as *recurring* requests, e.g. to add the
+previous example as a recurring request at 1Hz:
+
+ { "command": "diagnostic_request",
+ "action": "add",
+ "request": {
+ "bus": 1,
+ "id": 1234,
+ "mode": 1,
+ "pid": 5,
+ "frequency": 1
+ }
+ }
+ }
+
+To cancel a recurring request, send a `cancel` action with the same key, e.g.:
+
+ { "command": "diagnostic_request",
+ "action": "cancel",
+ "request": {
+ "bus": 1,
+ "id": 1234,
+ "mode": 1,
+ "pid": 5
+ }
+ }
+ }
+
+Simultaneous recurring requests for the same key at different rates (e.g. 1Hz
+*and* 2Hz) is not supported. However, non-recurring ("one-off") requests may
+exist in parallel with a recurring request for the same key.
+
+**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).
+
+**id** - the CAN arbitration ID for the request.
+
+**mode** - the OBD-II mode of the request - 0x1 through 0xff (1 through 9 are the
+ standardized modes and 0x22 is a common proprietary mode).
+
+**pid** - (optional) the PID for the request, if applicable.
+
+**payload** - (optional) up to 7 bytes of data for the request's payload
+ represented as a hexadecimal number in a string. Many JSON parser cannot
+ handle 64-bit integers, which is why we are not using a numerical data type.
+ Each byte in the string *must* be represented with 2 characters, e.g. `0x1`
+ is `0x01` - the complete string must have an even number of characters. The
+ `0x` prefix is optional.
+
+**name** - (optional, defaults to nothing) A human readable, string name for
+ this request. If provided, the response will have a `name` field (much like a
+ normal translated message) with this value in place of `bus`, `id`, `mode` and
+ `pid`.
+
+**multiple_responses** - (optional, false by default) if true, request will stay
+ active for a full 100ms, even after receiving a diagnostic response message.
+ This is useful for requests to the functional broadcast arbitration ID
+ (`0x7df`) when you need to get responses from multiple modules. It's possible
+ to set this to `true` for non-broadcast requests, but in practice you won't
+ see any additional responses after the first and it will just take up memory
+ in the VI for longer.
+
+**frequency** - (optional) Make this request a recurring request, at a this
+ frequency in Hz. To send a single non-recurring request, leave this field out.
+
+**decoded_type** - (optional, defaults to "obd2" if the request is a recognized
+OBD-II mode 1 request, otherwise "none") If specified, the valid values are
+`"none"` and `"obd2"`. If `obd2`, the payload will be decoded according to the
+OBD-II specification and returned in the `value` field. Set this to `none` to
+manually override the OBD-II decoding feature for a known PID.
+
+#### Responses
+
+The response to a successful request:
+
+ {"bus": 1,
+ "id": 1234,
+ "mode": 1,
+ "pid": 5,
+ "success": true,
+ "payload": "0x1234",
+ "value": 4660}
+
+and to an unsuccessful request, with the `negative_response_code` and no `pid`
+echo:
+
+ {"bus": 1,
+ "id": 1234,
+ "mode": 1,
+ "success": false,
+ "negative_response_code": 17}
+
+**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 requested node returned an error,
+ `success` will be `false` and this field will contain the negative response
+ code (NRC).
+
+Finally, the `payload` and `value` fields are mutually exclusive:
+
+**payload** - (optional) up to 7 bytes of data returned in the response,
+ represented as a hexadecimal number in a string. Many JSON parser cannot
+ handle 64-bit integers, which is why we are not using a numerical data type.
+
+**value** - (optional) if the response had a payload, this may be the
+ payload interpreted as an integer.
+
+The response to a simple PID request would look like this:
+
+ {"success": true, "bus": 1, "id": 1234, "mode": 1, "pid": 5, "payload": "0x2"}
+
+### Commands
+
+In addition to the `diagnostic_request` command described earlier, there are
+other possible values for the `command` field.
+
+#### Version Query
+
+The `version` command triggers the VI to inject a firmware version identifier
+response into the outgoing data stream.
+
+**Request**
+
+ { "command": "version"}
+
+**Response**
+
+ { "command_response": "version", "message": "v6.0-dev (default)"}
+
+#### Device ID Query
+
+The `device_id` command triggers the VI to inject a unique device ID (e.g. the
+MAC address of an included Bluetooth module) into into the outgoing data stream.
+
+**Request**
+
+ { "command": "device_id"}
+
+**Response**
+
+ { "command_response": "device_id", "message": "0012345678"}
+
+#### Passthrough CAN Mode
+
+The `passthrough` command controls the passthrough mode for each of the CAN
+buses. There are three passthrough modes:
+
+* `off` - Only the specified simple vehicle messages are processed and output
+ from the VI.
+* `filtered` - If the CAN acceptance filter is not otherwise disabled, only the
+ pre-defined CAN messages (i.e. those compiled with the firmware) will be
+ output in the low-level CAN format from VI.
+* `unfiltered` - All received CAN messages will be passed through from the bus
+ to the VI's output.
+
+**Request**
+
+ { "command": "passthrough"
+ "bus": 1,
+ "mode":
+ }
+
+**Response**
+
+If the bus and mode in the request were recognized, the `status` field in the
+response will be `true`. If `false`, the passthrough mode was not changed.
+
+ { "command_response": "passthrough", "status": true}
+
+### 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, degrees
+ * numerical, -600 to +600 degrees
+ * 10Hz
* torque_at_transmission
- * numerical, Nm
+ * numerical, -500 to 1500 Nm
+ * 10Hz
* engine_speed
- * numerical, RPM
-* vehicle_speed, numerical, Kph
+ * 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,
- 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, 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, liters (goes to 0 every time the
- vehicle interfaces power cycles)
+ * 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
+ * numerical, -89.0 to 89.0 degrees with standard GPS accuracy
+ * 1Hz
* longitude
- * numerical
+ * numerical, -179.0 to 179.0 degrees with standard GPS accuracy
+ * 1Hz
+
+### Signals from Diagnostics 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.
Code Review / apps / low-level-can-service.git / blobdiff