OpenWebNet

An OpenWebNet message is structured with variable length fields separated by the special character '*' and closed by '##'.

The characters admitted in the fields are numbers and the character “#”.

The structure of a message is therefore:

• field1*field2*… *fieldN##

The following fields are admitted: WHO WHAT WHERE DIMENSION VALUE

WHO

It characterizes the domotic system function to which the OpenWebNet message is referred.

For example: WHO = 1, characterizes the messages for lighting system management.

WHAT

It characterizes an action to do or a status to read. For every WHO (and therefore for every function) there is a specific WHAT table.

The field WHAT can also contain optional parameters: WHAT#PAR1#PAR2… #PARn.

Example of actions: switch ON light, dimmer to 75%, switch DOWN shutter, radio ON, etc. Example of status: light ON, active alarm, battery unload, etc.

WHERE

It characterizes the set of objects to which the OpenWebNet message is referred. It can be a single object, a group of objects, a specific environment, the entire system, etc.

For every WHO (and therefore for every function) there is a specified WHERE table.

The tag WHERE can also contain optional parameters: WHERE#PAR1#PAR2… #PARn.

Example of where: all the lights of group 1, sensor 2 of zone 1 of alarm system, etc.

DIMENSION

Is a range of value that characterizes the dimension of the object to which the message is referred. For every WHO (and therefore for every function) there is a specific DIMENSION table.

It’s possible to require/to read/to write the value of one dimension. Every dimension has a prefixed number of values, described in VALUE field.

Example of dimension: sensor temperature, loudspeaker volume, firmware version of a device, etc.

VALUE

It characterizes the read/written value of a written/required/read dimension.

There are 4 types of OpenWebNet Message:

• Command / Status Message
• Status Request Message
• Request/Read/Write Dimension Message
• Acknowledge Message

Command / Status Message

*WHO*WHAT*WHERE##

Status Request Message

*#WHO*WHERE##

Request/Read/Write Dimension Message Request:

*#WHO*WHERE*DIMENSION##

Read:

*#WHO*WHERE*DIMENSION*VALUE1*...*VALUEn##

Write:

*#WHO*WHERE*#DIMENSION*VALUE1*...*VALUEn##

Acknowledge Message ACK:

*#*1##

NACK:

*#*0##

The current implementation by BTicino is also an embedded web server. It works as a translator between OpenWebNet messages via TCP/IP and the SCS messages transmitted on the SCS bus.

It is possible to control three different kinds of buses:

• BUS SCS
• KNX
• DMX

The Ethernet gateway offers two modes of authentication:

• via a list of whitelisted IPAs
• using a nonce-type password exchange (see in the external links for code)

The gateway is an interface that works as a translator between the OpenWebNet messages transmitted on USB or serial and the SCS messages transmitted on the SCS bus.