# OpenXC Message Format Specification
+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
The expected format of a single valued message is:
-{% highlight javascript %}
-{"name": "steering_wheel_angle", "value": 45}
-{% endhighlight %}
+ {"name": "steering_wheel_angle", "value": 45}
## Evented
The expected format of an event message is:
-{% highlight javascript %}
-{"name": "button_event", "value": "up", "event": "pressed"}
-{% endhighlight %}
+ {"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}
+
+**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 0xf (0x1 through 0xa
+ are the standardized modes).
+
+**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 hexidecimal number in a string. Many JSON parser cannot
+ handle 64-bit integers, which is why we are not using a numerical data type.
+
+**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.
+
+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
+
+## Trace File Format
+
+An OpenXC vehicle trace file is a plaintext file that contains JSON objects,
+separated by newlines.
+
+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,
+ reverse, neutral
+ * 1Hz, but sent immediately on change
+* gear_lever_position
+ * states: neutral, park, reverse, drive, sport, low, first, second, third,
+ fourth, fifth, sixth
+ * 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
+
+License
+=======
+
+Copyright (c) 2012-2013 Ford Motor Company
+
+Licensed under the BSD license.
+
+[OpenXC]: http://openxcplatform.com
Code Review / apps / low-level-can-service.git / blobdiff