Access Functions

Protocol Modes

Similar to Modbus, the ThingSet protocol supports two different modes: A human-readable text mode and a binary mode.

In the text mode, payload data is encoded in JSON format (RFC 8259open in new window). This mode is recommended when using serial communication interfaces as the low layer protocol, as it can be easily used directly on a terminal.

The binary mode uses CBOR (RFC 8949open in new window) instead of JSON for payload data encoding in order to reduce the protocol overhead for ressource-constrained devices or low bandwith communication via CAN or LoRa.

A device may implement both variants of the protocol, but it is also allowed to support only the mode most suitable for the application.

The first byte of a ThingSet message is either a text-mode identifier (?, =, !, +, -, :, @ and #), a binary request code or a binary status code. Received data with unknown first byte is ignored, so that other text output (e.g. debug print information) can be used in parallel to the ThingSet protocol on the same serial interface.


The protocol supports the typical CRUD operationsopen in new window. Request codes match with CoAP to allow transparent mapping between ThingSet and CoAP devices.

Binary modeText modeFunctionCoAP equivalentDescription
0x01?GETGETRetrieve all data from a path
0x05?FETCHFETCHRetrieve a part of the data from a path
0x07=UPDATEiPATCHUpdate (overwrite) data of a path
0x06+CREATEPATCHAppend data to an object
0x04-DELETEDELETEDelete data from an object
0x02!EXECPOSTExecute a function

The CoAP PUT method is not explicitly implemented. PUT is equivalent to an update of all sub-objects of a resource using a PATCH request. UPDATE requests for ThingSet are always idempotent, so only the iPATCH request code is used. The PATCH method is used to create new data.

Additional request codes may be introduced in the future. Codes 0x0A, 0x0D and 0x20-0x7F are reserved, as they represent the ASCII characters for readable text including LF and CR.


Response messages in binary format are identified by a first byte greater than or equal to 128 (0x80) containing a status code which shows if the request could be handled successfully. For status codes between 0x80 and 0x9F, the response was successful. If the status code is greater than or equal to 0xA0, an error occured.

The status codes are again aligned with CoAP response codesopen in new window, but contain an offset so that there is no interference with ASCII characters (less than 0x80).

0x812.01201CreatedAnswer to CREATE requests
0x822.02204DeletedAnswer to DELETE request
0x842.04200/204ChangedAnswer to EXEC and UPDATE requests
0x852.05200ContentAnswer to GET and FETCH requests
0xA04.00400Bad Request
0xA14.01401UnauthorizedAuthentication needed
0xA34.03403ForbiddenTrying to write read-only value
0xA44.04404Not Found
0xA54.05405Method Not AllowedIf e.g. DELETE is not allowed for that object
0xA84.08400Request Entity Incomplete
0xA94.09409ConflictConfiguration conflicts with other settings
0xAD4.13413Request Entity Too Large
0xAF4.15415Unsupported Content-FormatIf trying to assign a string to an int
0xC05.00500Internal Server ErrorGeneric catch-all response
0xC15.01501Not ImplementedRequest method is not supported
0xC45.04504Gateway TimeoutNode cannot be reached through gateway
0xC55.05505Not a GatewayNode is not a gateway and does not support absolute paths

Responses text mode use the colon : as the first byte identifier, followed by the hexadecimal response code converted into a string without the 0x prefix. The binary mode uses the code directly as the first byte.

Desires and Reports

Desires and reports are neither requests nor response messages, as they are sent without expecting a confirmation. Below table lists the message specifiers in text and binary mode.

Binary modeText modeDescription

The overlay _Reporting is used to configure the device to publish certain data items on a regular basis through a defined communication channel (UART, CAN, LoRaWAN, etc.). If implemented in the firmware, the publication interval may be adjustable.

More details regarding the ThingSet protocol methods for data access will be explained in the next chapter.