L. Emery, M. Borland, H. Shang, R. Soliday
Advanced Photon Source
May 7, 2008
The SDDS-compliant EPICS toolkit is a set of software applications for the collection or writing of data in Experimental Physics and Industrial Control System (EPICS) database records. Though most of the applications essentially do rather simple operations, the combination of these and others from the SDDS postprocessing toolkit allow arbitrarily complicated analysis of data and control of the accelerators at the Advanced Photon Source. These tools are general and can be applied to devices other than accelerators under control of EPICS.
The EPICS tools presented here read and store data to SDDS-protocol files. SDDS (Self-Describing Data Set) refers to a particular implementation of a self-describing file protocol used at APS. Self-describing means that the data is refered to and accessed by name. Thus, a user doesn't need to know, say, in which column a piece of tabular data is located. An ASCII header contains information about the file's data structure, i.e. definitions of structure elements such as columns (tabular data) and parameters (single values).
Initially adopted for complex physics simulation programs, it was clear that the SDDS file protocol would excel in data-collecting software as well. Typically, an EPICS tool would write EPICS data to an SDDS file with each readback written to a column of name corresponding to the EPICS database record name. Single value data that describe the experimental conditions might be written to the file as parameters. Once collected, the EPICS data can be further analyzed and plotted with any of the SDDS tools described in . One can regard the EPICS tools as the layer between the EPICS control system and more functional analyzing tools and scripts, with SDDS protocol files as an intermediary.
Following conventional usage, EPICS database records will be refered to as ``process variables'' or PVs in this manual.