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).
-## 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.
+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.
-### 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.
-
-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
-
-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 whether low-level CAN messages are passed
-through from the CAN bus through the VI to the output stream. If the CAN
-acceptance filter is in bypass mode and passthrough is enabled, the output
-stream will include all received CAN messages. If the bypass filter is enabled,
-only those CAN messages that have been pre-defined in the firmware are
-forwarded.
-
-**Request**
-
- { "command": "passthrough",
- "bus": 1,
- "enabled": true
- }
-
-**Response**
-
-If the bus in the request was valid and the passthrough mode was changed, the
-`status` field in the response will be `true`. If `false`, the passthrough mode
-was not changed.
-
- { "command_response": "passthrough", "status": true}
-
-#### Acceptance Filter Bypass
-
-The `af_bypass` command controls whether the CAN message acceptance filter is
-bypassed for each CAN controller. By default, hardware acceptance filter (AF) is
-enabled in the VI - only previously defined CAN message IDs will be received.
-Send this command with `bypass: true` to force the filters to bypassed.
-
-If `passthrough` mode is also enabled, when the AF is bypassed, the output will
-include all CAN messages received.
-
-**Request**
-
- { "command": "af_bypass",
- "bus": 1,
- "bypass": true
- }
-
-**Response**
-
-If the bus in the request was valid and the AF mode was changed, the `status`
-field in the response will be `true`. If `false`, the passthrough mode was not
-changed.
-
- { "command_response": "af_bypass", "status": true}
-
-#### Payload Format Control
-
-The `payload_format` command determines the format for output data from the VI
-and the expected format of commands sent to the VI.
-
-Valid formats are `json` and `protobuf`.
-
-**Request**
-
- { "command": "payload_format",
- "format": "json"
- }
-
-**Response**
-
-If the format was changed successfully, the `status` in the response will be
-`true`. The response will be in the original message format, and all subsequent
-messages will be in the new format.
-
- { "command_response": "payload_format", "status": true}
-
-#### Automatic Pre-Defined OBD-II PID Requests
-
-The `predefined_obd2` command enables and disables the querying for and
-translating of a set of pre-defined OBD-II PIDs from the attached vehicle. When
-enabled, the VI will query the vehicle to see if these PIDs are claimed to be
-supported and for those that are, it will set up recurring requests. The
-responses will be output as simple vehicle messages, with the names defined in
-the "Signals Defined from Diagnostic Messages" section below.
-
-**Request**
-
- { "command": "predefined_obd2",
- "enabled": true
- }
+## Binary (Protocol Buffers)
-**Response**
+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.
-f the predefined requests were enabled or disabled successfully, the `status` in
-the response will be `true`.
+The binary messages are published by the VI using the standard length-delimited
+method (any protobuf library should support this).
- { "command_response": "predefined_obd2", "status": true}
+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
+## 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
* numerical, -179.0 to 179.0 degrees with standard GPS accuracy
* 1Hz
-### Signals from Diagnostic Messages
+## 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).
Code Review / apps / low-level-can-service.git / blobdiff