SWAP Protocol Decoder Encoder

SWAP Protocol Decoder Encoder

The Simple WSN Application Protocol (SWAP) Protocol

The SWAP protocol provides an easy and lightweight alternative to service oriented application level protocols like the Constrained Application Protocol (CoAP). As packages may get larger than e.g., the MTU of 802.15.4, one usually runs the SWAP protocol on base of a fragmenting protocol such as the Remote UART protocol.

Implementations

Message Types

Request Message

0:   CMD_TYPE = 70
1:   REQUEST_ID
2:   REQUEST_TYPE
3:   REQUEST_OPTIONS_LENGTH
4-n: REQUEST_OPTIONS

Response Message

0:   CMD_TYPE = 71
1:   REQUEST_ID
2:   RESPONSE_CODE
3:   RESPONSE_PAYLOAD_LENGTH
4-n: RESPONSE_PAYLOAD

Push Message

0:   CMD_TYPE = 72
1:   SUBSCRIPTION_ID
2:   PAYLOAD_LENGTH
3-n: PAYLOAD

Possible Values for Requests, Responses and Push Messages

Request -> Response

The following table shows the possible values for the various fields of request and response messages:

REQUEST_TYPE	REQUEST_OPTIONS	RESPONSE_PAYLOAD
0x00 GET_SENSORS		newline character-separated string of sensor names and associated key-value pairs, e.g., "temp=1\nhumid=2\nacc=3"
0x01 GET_SENSORNODE_META_DATA		key-value pairs, newline character-separated, e.g., "type=isense\nrevision=jennic85391"
0x02 GET_SENSOR_VALUE	1 byte uint_8, identifying the sensor, e.g. "1", see GET_SENSORS	sensor-specific binary representation of a sensor value, see below
0x03 GET_SENSOR_META_DATA	1 byte uint_8, identifying the sensor, e.g. "1", see GET_SENSORS	key-value pairs, newline character-separated, e.g., "type=temperature\nunit=degreecelsius"
0x04 SUBSCRIBE	key-value pairs, newline character-separated, e.g., "method=push\nduration=7200000"	1 byte subscription ID
0x05 UNSUBSCRIBE	1 byte subscription ID
0x06 PUT_SENSOR_META_DATA	1 byte identifying the sensor, e.g., "1", 1 byte string length, string with meta data as key-value pair, e.g., "type=temperature"	empty response with an appropriate response code

Push

The data representation of a push messages' PAYLOAD field is defined below (sensor-specific binary representation of sensor values).

Sensor-Specific Binary Representation of Sensor Values

Sensor values are encoded as 3-tuples of the following form:

ENCODING_BYTE

DATA_LENGTH (in byte)

DATA

The `ENCODING_BYTE` takes, depending on the value to be encoded, one of the following values:

UNKNOWN_ENCODING	0xff
BOOL	0x01
UINT8	0x02
INT8	0x03
UINT16	0x04
INT16	0x05
UINT32	0x06
INT32	0x07
UINT64	0x08
INT64	0x09
STRING	0x0a
DOUBLE	0x0b

`DATA_LENGTH` defines the length of the value in `DATA`, e.g., "1" for `ENCODING_BYTE = 0x02` (UINT8).

Sensor Meta Data Representation

room = int
type = temp | occupation
unit = celsius/fahrenheit (bei temp) | bool (bei occupation)
position = gps