ArtTrigger

ArtTrigger

The ArtTrigger packet is used to send triggers and macros to the network. There is no reply packet.

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Broadcast and Unicast algorithms

The ArtTrigger packet can be broadcast or unicast to the network. The decision on which to use is application specific. The most common implementation involves a single controller broadcasting to all other devices.

In some circumstances a controller may only wish to trigger a single device or a small group in which case unicast would be used.

ArtTrigger – Packet Definition

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ID

The ID field is 8 bytes in length and contains the null terminated string of ASCII characters:

A r t – N e t

The purpose of the field is to identify the packet as an Art-Net protocol packet. All Art-Net packets start with this field. Receivers must check this field is correct and discard the packet if it is not.

OpCode

The OpCode field is a 16-bit word transmitted low byte first. The OpCode identifies the packet type. In the ArtTrigger packet this field is set to ‘OpTrigger’.

ProtVer

The ProtVer field is a 16-bit word transmitted high byte first. It identifies the version of the Art-Net protocol. The protocol version is not related to Art-Net 1, II, 3 or 4. Only one protocol version has ever existed in production equipment which is 1410. Receivers should use the following good packet test:

ProtVer >= 14

The ProtVer may be increased in a future releases to identify significant functionality changes.

Filler1-2          

These fields are used to pad the length of this packet to match the ArtPoll header. They are transmitted as zero and never tested by receivers.

Oem   

The OEM Code is a 16-bit number which uniquely defines the Art-Net products which should process this packet. A value of ffff16 is the ‘global’ value which means that all devices should process the message.

Key     

The Key is an 8-bit number which defines the purpose of the packet. The interpretation of this field is dependent upon the Oem field. If the Oem field is set to a value other than ffff16 then the Key and SubKey fields are manufacturer specific.

However, when the Oem field = ffff16 the meaning of the Key, SubKey and Payload is defined by the following table:

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SubKey

The SubKey is an 8-bit number. The interpretation of this field is dependent upon the Oem field. If the Oem field is set to a value other than ffff16 then the Key and SubKey fields are manufacturer specific.

However, when the Oem field = ffff16 the meaning of the SubKey field is defined by the table above.

Payload         

The Payload is a fixed length array of 512, 8-bit bytes. The interpretation of this field is dependent upon the Oem field. If the Oem field is set to a value other than ffff16 then the Payload is manufacturer specific.

Currently when the Oem field = ffff16 the Payload is not defined, although it is often used for informational text to aid system debugging.