Standard Properties

Introduction

INDI does not place any special semantics on property names (i.e. properties are just texts, numbers, or switches that represent no physical function). While GUI clients can construct graphical representation of properties in order to permit the user to operate the device, we run into situations where clients and drivers need to agree on the exact meaning of some fundamental properties.

What if some client need to be aware of the existence of some property in order to perform some function useful to the user? How can that client tie itself to such a property if the property can be arbitrary defined by drivers?

The solution is to define Standard Properties in order to establish a level of interoperability among INDI drivers and clients. We propose a set of shared INDI properties that encapsulate the most common characteristics of astronomical instrumentation of interest.

If the semantics of such properties are properly defined, not only it will insure base interoperability, but complete device automation becomes possible as well. Put another way, INDI standard properties are in essence properties that represent a clearly defined characteristic related to the operation of the device drivers.

For example, a very common standard property is EQUATORIAL_EOD_COORD. This property represents the telescope’s current RA and DEC. Clients need to be aware of this property in order to, for example, draw the telescope’s cross hair on the sky map. If you write a script to control a telescope, you know that any telescope supporting EQUATORIAL_EOD_COORD will behave in an expected manner when the property is invoked.

INDI clients are required to honor standard properties if when and they implement any functions associated with a particular standard property. Furthermore, INDI drivers employing standard properties should strictly adhere to the standard properties structure as defined next.

General

The following tables describe standard properties pertaining to generic devices and class-specific devices like telescope, CCDs…etc. The name of a standard property and its members must be strictly reserved in all drivers. However, it is permissible to change the label element of properties. You can find numerous uses of the standard properties in the INDI library driver repository.

ACTIVE_DEVICES is used to aid clients in automatically providing the users with a list of active devices (i.e. CONNECTION is ON) whenever needed. For example, a CCD driver may define ACTIVE_DEVICES property with one member: ACTIVE_TELESCOPE. Suppose that the client is also running LX200 Basic driver to control the telescope. If the telescope is connected, the client may automatically fill the ACTIVE_TELESCOPE field or provide a drop-down list of active telescopes to select from. Once set, the CCD driver may record, for example, the telescope name, RA, DEC, among other metadata once it captures an image. Therefore, ACTIVE_DEVICES is primarily used to link together different classes of devices to exchange warnrmation if required.

Telescopes

Telescope standard properties define critical properties for the operation and control of the mount. In addition to the properties below, all properties in INDI Alignment Subsystem are considered standard properties as well and must be reserved in all implementations.

For clients that want to implement the GOTO functionality of a telescope, they should expect telescope drivers to define either:

• EQUATORIAL_EOD_COORD for current Epoch; and/or
• HORIZONTAL_COORD.

CCDs

Most CCD_* properties are also applicable to GUIDER chip, so replace CCD with GUIDER above to define properties for the GUIDER chip, if applicable.

Streaming

Some CCD drivers support streaming and recording of video streams. All the properties defined in StreamManager are considered reserved standard properties. The stream data is sent via the same CCD1 BLOB used for image transmission and therefore it is not possible to stream and send regular CCD captures at the same time.

• _D_ is replaced with the date (‘YYYY-MM-DD’)
• _H_ is replaced with the time (‘hh-mm-ss’)
• _T_ is replaced with a timestamp
• _F_ is replaced with the filter name currently in use

| | RECORD_FILE_DIR | Directory to save the file. It defaults to $HOME/indi__D_ | | RECORD_FILE_NAME | Recording file name. It defaults to indi_record__T_ | | RECORD_OPTIONS | Switch | | Set the desired duration in seconds or total frames required for the recording. | | RECORD_DURATION | Duration in seconds. | | RECORD_FRAME_TOTAL | Total number of frames required | | RECORD_STREAM | Switch | | Start or Stop the stream recording to a file. | | RECORD_ON | Start recording. Do not stop unless asked to. | | RECORD_DURATION_ON | Start recording until the duration set in RECORD_OPTIONS has elapsed. | | RECORD_FRAME_ON | Start recording until the number of frames set in RECOR_OPTIONS has been captured. | | RECORD_OFF | Stops recording. |

Filter wheels

Focusers

Domes