If you use TachyCAD on a Trimble Total Station, at the end of the installation process, enable the Install Trimble Precision SDK (TPSDK) option. By default, this option is disabled.
If you get a message stating .NET Framework version 3.5 is missing, install the feature. An internet connection is required for installation otherwise the Microsoft installer will abort.
The "Tell me more about this feature" link in the dialog box above, provides additional information from the following Microsoft help article: Install the .NET Framework 3.5 on Windows 10, Windows 8.1, and Windows 8.
software development toolkit, total station interface