Flexible image acquisition using reconfigurable hardware

We describe the use of a reconfigurable interface board based on FPGAs in a high bandwidth image acquisition system. We show that a generic interface board can be readily adapted to three quite different CCD image sensors. Our guiding philosophy is to implement the entire interface in programmable logic. We depart from this principle only for electrical adaptation which is performed by relatively simple daughter boards. The CCDs we describe are used for data collection and telescope control at the Swedish Vacuum Solar Telescope located at the Rogue de los Muchachos, La Palma, Canary Islands, where various versions of our interface have been in use since May 1993. Reconfigurable solutions are particularly well suited to this application which is inherently low volume and requires many minor variants in response to changing experimental conditions. The CCDs used deliver image data at 10-30 MB/s. Our interfaces cope comfortably with multiple CCDs operating continuously at this rate on a single host, while also performing low bandwidth servo control tasks. We present the structure of the CCD interface configurations and the design issues that arose during their development. Reconfigurability allows the interface configurations and supporting software to be developed together leading to efficient, tightly coupled, total system solutions.