**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.
+ 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.
## Diagnostic Messages
### Requests
- {"bus": 1,
- "id": 1234,
- "mode": 1,
- "pid": 5,
- "payload": "0x1234",
- "frequency": 0}
+A request to add or update a diagnostic request is sent to a vehicle interface
+with this command format:
+
+ { "command": "diagnostic_request",
+ "request": {
+ "bus": 1,
+ "id": 1234,
+ "mode": 1,
+ "pid": 5,
+ "payload": "0x1234",
+ "parse_payload": true,
+ "multiple_responses": false,
+ "factor": 1.0,
+ "offset": 0,
+ "frequency": 1,
+ "name": "my_pid"
+ }
+ }
+ }
**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).
+**mode** - the OBD-II mode of the request - 1 through 15 (1 through 9 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.
+ 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.
+
+**parse_payload** - (optional, false by default) if `true`, the complete payload
+ in the response message will be parsed as a number and returned in the
+ `value` field of the response. The `payload` field will be omitted in
+ responses with a `value`.
+
+**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.
+
+**factor** - (optional, 1.0 by default) if `parse_payload` is true, the value in
+ the payload will be multiplied by this factor before returning. The `factor`
+ is applied before the `offset`.
+
+**offset** - (optional, 0 by default) if `parse_payload` is true, this offset
+ will be added to the value in the payload before returning. The `offset` is
+ applied after the `factor`.
**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
+The `bus+id+mode+pid` key is unique, so if you send a create request with that
+key twice, it'll overwrite the existing one (i.e. it will change the frequency,
+the only other parameter). To cancel a recurring request, send this command with
+the frequency set to 0.
-If you're just requesting a PID, you can use a simplified format for the
-request:
+If you're just requesting a PID, you can use this minimal field set for the
+`request` object:
{"bus": 1, "id": 1234, "mode": 1, "pid": 5}
### Responses
+The response to a successful request:
+
{"bus": 1,
"id": 1234,
"mode": 1,
"pid": 5,
"success": true,
- "negative_response_code": 17,
- "payload": "0x1234"}
+ "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.
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,
+**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 hexidecimal number in a string. Many JSON parser cannot
+ 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.
-The response to a simple PID requset would look like this:
+**value** - (optional) if the response had a payload, this may be the
+ payload interpreted as an integer and transformed with a factor and offset
+ provided with the request.
+
+The response to a simple PID request would look like this:
+
+ {"success": true, "bus": 1, "id": 1234, "mode": 1, "pid": 5, "payload": "0x2"}
+
+## Commands
+
+### 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"}
- {"bus": 1, "id": 1234, "mode": 1, "pid": 5, "payload": "0x2"}
+**Response**
-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
+ { "command_response": "device_id", "message": "0012345678"}
## Trace File Format