|Cosmic Background Imager|
Control and data acquisition are divided between two computers, a real-time system running VxWorks1 on a single-board computer mounted in a VME crate2, and a Sun Microsystems3 workstation. The real-time system controls and monitors the CBI hardware via a VME backplane. Some 3000 registers, including the observed complex visibilities (10 channels times 78 baselines), are monitored every 0.8 s and sent via TCP/IP to the Sun. The Sun control program runs continuously and is responsible for data logging, executing commands received from users, and executing schedules written in a specially designed embedded scheduling language. A powerful user-interface program can be run on the same Sun or on a remote workstation. This is implemented as a set of C service functions layered under a Tcl/Tk graphical user interface (GUI) and provides real-time graphical and textual monitoring facilities, along with a command-line control interface. It can be used both to display the current instrumental status and to examine or replay archived log data. Archived data are transferred on magneto-optical disks to San Pedro for analysis.
Two Sun workstations (primary control and backup) in the control room (October 1999). Extra cooling fans are required because of the low pressure; hard disks are enclosed in pressurized containers.