ProxyExt properties

Regardless of the driver, the proxy extension (ProxyExt) for any proxy point has a number of core properties that provide the same behavior. Depending on the driver, other ProxyExt properties are often present—see the particular driver document for details on those properties.

Core properties in any ProxyExt include the following:

Status

(read only) Status of the proxy extension, which in turn determines parent point status. See Proxy point status.
Fault Cause

(read only) If point has fault status, provides text description why.
Enabled

Either true (default) or false. While set to false, the point’s status becomes disabled and polling is suspended.
Device Facets

(read only) Native facets used in proxy read or writes (Parent point’s facets are used in point status display, and are available for edit in Add and Edit dialogs in Point Manager).
Conversion

Specifies the conversion used between the “read value” (in Device Facets) and the parent point’s output (in selected point facets).
In most cases, except when working with particular Ndio proxy points, or perhaps Modbus proxy points, the standard “Default” conversion selection is best.

Conversion selections include:
- Default
  
  (The default selection). Conversion between “similar units” is automatically performed within the proxy point. For example, if a Lon proxy point with a LonFloatProxyExt (Device Facets of degrees C), if you set the point’s Facets to degrees F, its output value automatically adjusts.
  
  If you set the parent point’s Facets to dissimilar units (say, in this case to kilograms), the parent point has a fault status to indicate a configuration error.
- Linear
  
  Applies to certain Ndio proxy points, such as NdioVoltageInput and NdioResistiveInput. Also commonly used in some Modbus proxy points. For these points, you typically want the point’s output value in some units other than Device Facets (if Ndio, voltage or resistance), and the Linear selection provides two fields to make the transition:
  - Scale: Determines linear response slope.
  - Offset: Offset used in output calculation.
- Reverse Polarity
  
  Useful in a Boolean-type Ndio proxy point to reverse the logic of the hardware binary input. Also, may be used in any driver’s proxied BooleanPoint, as a way to “flip” the read state of the native value.
  Be careful in the use of the reverse polarity conversion, as it may lead to later confusion when troubleshooting logic or communications problems.
- Thermistor Type 3
  
  Applies to an NdioThermistorInput point, where this selection provides a “built-in” input resistance-to-temperature value response curve for Type 3 Thermistor temperature sensors.
- Tabular Thermistor
  
  Applies to an NdioThermistorInput point, where this selection provides a control for a popup dialog for a custom resistance-to-temperature value response curve, including ability to import and export response curves.
Tuning Policy Name

(most drivers) Associated network tuning policy for this proxy point, by name. Tuning policies are used to separate poll rates and other driver features. See About Tuning Policies.
Read Value

(read only) Last value read from the device, expressed in device facets.
Write Value

(read only) Applies if writable point only. Last value written, using device facets.