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def
writable-point
Point with writable output using 16-level priority array. Writable points typically are a setpoint or actuator command. Haystack writable points are modeled on the BACnet 16-level priority array with a relinquish default which effectively acts as level 17.
The following levels have special behavior:
- Level 1: highest priority reserved for emergency overrides
- Level 8: manual override with ability to set timer to expire back to auto
- Default: implicitly acts as level 17 for relinquish default
The priority array provides for contention resolution when many different control applications may be vying for control of a given point. Low level applications like scheduling typically control levels 14, 15, or 16. Then users can override at level 8. But a higher levels like 2 to 7 can be used to trump a user override (for example a demand response energy routine that requires higher priority).
The actual value to write is resolved by starting at level 1 and working down to relinquish default to find the first non-null value. It is possible for all levels to be null, in which case the overall write output is null (which in turn may be auto/null to another system). Anytime a null value is written to a priority level, we say that level has been set to auto or released (this allows the next highest level to take command of the output).
Also see Points chapter.
conjunct
meta
usage
supertypes
| marker |
Marker labels a dict with typing information |
|---|---|
| entity |
Top-level dicts with a unique identifier |
| point |
Data point such as a sensor or actuator |
tags
| cur |
Supports current value |
|---|---|
| dis |
Display name for an entity |
| enum |
Defines an eumeration of string key names |
| equipRef |
Reference to equip which contains this entity |
| his |
Supports historization of data |
| id |
Defines the unique identifier of an entity in system using a |
| kind |
Kind name used to identity a value data type |
| maxVal |
Inclusive maximum for a numeric value |
| minVal |
Inclusive minimum for a numeric value |
| pointFunction |
Classifies the point as a sensor, command, or setpoint |
| pointQuantity |
Quantity the point senses or controls |
| pointSubject |
What the point senses or controls |
| siteRef |
Reference to site which contains the entity |
| spaceRef |
Reference to space which contains this entity |
| systemRef |
Reference to system |
| tz |
Timezone identifier from standard timezone database |
| unit |
Unit identifier from standard unit database |
| vfd |
Variable-frequency drive |
| writable |
Supports writing data |
| writeErr |
Error description when |
| writeLevel |
Current priority level for |
| writeStatus |
Current status of a writable point output |
| writeVal |
Current desired value to write to output |