Signal Flow Tools

Table of Contents

• The Signal Flow Service Provider
  • Signal Bridges
    • Accessing Signal Bridges
• The Signal Flow I/O Driver
  • Registers
    • Register Blocks
    • Accessing Registers
    • Accessing Register Blocks

The Signal Flow Service Provider

Xentara has a built-in service provider named SignalFlow. This service provider provides element types that can be used to direct signal and data flow within Xentara.

Signal Bridges

Signal bridges are microservices that copy the values from one attribute to another. Each bridge consists of a number of connection between a readable attribute of a Xentara element, and a writable attribute of the same or of a different Xentara element. Whenever the copy operation is triggered, all the values are read from the source attributes and copied to the corresponding target attributes.

Normally, a signal bridge only copies the attribute values in the operational stage. A bridge can be configure to copy the values in any stage, however.

Signal bridges expose a single task named copy that performs the copying. You can insert that task into an execution pipeline and attach it to a timer or an event. To refer to the task, use its primary key. The primary key of the copy task of a signal bridge called “My.Signal.Bridge” is “My.Signal.Bridge.copy”.

Accessing Signal Bridges

Signal bridges have the following members:

Attributes

key	The signal bridge’s primary key.
name	The signal bridge’s name. The name is the last component of the primary key.
UUID	The unique UUID of the signal bridge.

Tasks

copy	Copies the values from the source attributes to the target attributes

To refer to a member, use its primary key. The primary key of the copy task of a signal bridge called “My.Signal.Bridge” is “My.Signal.Bridge.copy”.

The Signal Flow I/O Driver

Xentara also has a built-in I/O driver named SignalFlow. Like the service provider, this driver provides element types that can be used to direct signal and data flow within Xentara.

Registers

Registers are I/O points that store a settable value. The register is initialized with a default value, and can be modified by writing to its “value” attribute.

Registers can be used if a value that is written by some external source, like the Xentara Web Service, needs to be accessed later by other components. The value can then be stored in a register, and read back as needed.

Register Blocks

Registers are grouped together into I/O components called “register blocks”. Register blocks have no functionality themselves; they are only containers for registers.

Accessing Registers

Registers have the following members:

Attributes

key	The register’s primary key.
name	The register’s name. The name is the last component of the primary key.
UUID	The unique UUID of the register.
value	The current value of the regfister. This attribute can be written to to change the stored value.
updateTime	The last time a value was written to the register. This attribute is always the same as the writeTime attribute.
writeTime	The last time a value was written to the register. This attribute is always the same as the updateTime attribute.
quality	The quality of the register value. The quality of a register is always “good” and never changes.
changeTime	The last time the value changed. Contrary to the writeTime and updateTime attribute, this time stamp is not updated if the same value is written multiple times.

Events

value	This event is emitted whenever the value changes.
quality	This event would normally be emitted whenever the quality changes. Since the quality of a register is always “good”, and never changes, this event is never sent. It only exists to keep the interface consistent with other types of I/O points.
written	This event is emitted whenever the value is written, whether it changed or not.
changed	This event would normally be emitted when either the value or the quality changes. Since the quality of a register is always “good”, and never changes, this event is equivalent to the value event.

To refer to a member, use its primary key. The primary key of the value attribute of a register called “My.Register” is “My.Register.value”.

Accessing Register Blocks

Register Blocks only have the default members that all Xentara elements have:

Attributes

key	The register block’s primary key.
name	The register block’s name. The name is the last component of the primary key.
UUID	The unique UUID of the register block.

To refer to a member, use its primary key. The primary key of the UUID attribute of a register block called “My.Register.Block” is “My.Register.Block.UUID”.