TopBox User Manual


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Motor Control

The two filter wheels and the autoguider linear positioner have nearly identical programmable control units which communicate with a control computer through RS-232 serial ports. In the TopBox electronics a single serial line from the control computer is daisy-chained to all three controllers. A terminal application on the control computer can connect to the TTY interface of any one of the three motor controllers to transmit text commands from the keyboard. Each motor controller supports editing, storage, and execution of control programs.

Focus Control

The autoguider focuser is motor driven and has an encoder for absolute or relative postioning. An RS-232 serial line from the control computer is connected to the focus controller box, which is mounted inside the TopBox electronics enclosure. The controller box has manual pushbutton controls, but it is normally operated over the serial line from its own graphical software interface on the control computer. The main camera control application (MaxImDL) can also provide the autoguider focus control interface by an ASCOM link to the same software.

Robotic Observatory Control System Integration

The control modes described above give direct access to the TopBox filter wheels, autoguider positioner, and focuser for testing and adjustment. For routine automated operation of the observatory system the TopBox is controlled by an ASCOM Filter Wheel driver for MaxImDL.

The driver is a Windows DLL assembled in Microsoft Visual Basic 2010 Express Edition (free software including Microsoft .NET Framework 4) according to templates and instructions included in the ASCOM Platform Version 5.5 (also free software), with additions from the ASCOM software developer kit (SDK). Within the structure of the ASCOM IFilterWheel interface template, the filter wheels are controlled by an ASCII dialog with the motor controllers over a serial interface, using the ASCOM Serial Helper Utilities.

In ASCOM teminology, this driver is a .NET assembly (dll). It is an "in-process driver," as opposed to a "local server," and it implements a master interface for early binding by clients. The driver was compiled for .NET Framework 3.5 because that is the standard for the ASCOM Platform Version 5.5 running on the control computer.

The driver should be installed by running the installer program "TopBox2.9Setup.exe" generated by Inno Setup (another free software package) according to the ASCOM SDK instructions. An uninstaller will be created in the directory C:\Program Files\Common Files\ASCOM\Uninstall\FilterWheel\TopBox2\.

Because MaxImDL does not directly implement the ASCOM FilterWheel driver interface, filter wheel control must be configured in the MaxImDL Camera Control Setup by selecting ASCOM for filter wheel, then using the Advanced button to choose "TopBox2 FilterWheel" as the driver, then setting its Properties to use the COM port that is connected to the PC Motor Jack of the TopBox electronics rack (currently COM15). More detailed instructions on how to set up the DualWheels filter wheel plugin and the SBIG STL-1001E CCD Camera with its internal filter wheel and external autoguider head can be found in the MaxImDL Help manual.

The TopBox2 Filter Wheel driver V2.9 also includes automation functions to query the GSC to find a guide star, then position and adjust the focus of the autoguider camera. The autoguider focuser is linked through an ASCOM Pipe interface to the focuser driver, which uses the COM port that is connected to the PC Focuser Jack of the TopBox electronics rack (currently COM4).

Last modified: Sep 13, 2012
David McDavid