Fasti is an innovative design for infrared and fast optical detectors and is mainly implemented as software. All circuit logic is built using programmable chips, the sequence generator is a specialized microprocessor build in a PGA (Programmable Gate Array), all the system is controlled by a Linux embedded controller, the waveforms are described by an ad hoc assembler.
Fasti is meant to be a light electronic system, and is designed to be modular, flexible, extendible and to avoid obsolescence as much as possible. It is divided into modules with clear-cut boundaries. Fasti is seen as a network device, giving very few constraints to the controlling architecture. Fasti can hold up to four completely different waveforms, so is capable of controlling the detector in radically different operation modes.
The first uses of Fasti will be the replacement of the Nics (Nics is the Infrared Camera Spectrometer developed by Arcetri Infrared Group for the TNG, the Italian National Telescope Galileo, see Baffa et al. 2001) electronics and the fast LBT (Large Binocular Telescope) wavefront sensor optical detectors control (Esposito et al. (2002), Foppiani et al. (2002)).
Fasti is designed as modules, its structure can be seen in Figure 1. Fasti building blocks are:
We describe briefly the main modules.
The flexible waveform generator is a custom part of which we had already built the prototype. It is based on a specialized micro-controller, where the waveform definition is built by means of a program in a pseudo assembler language, greatly simplifying the definition of new waveforms. We had already developed all the support software for waveform design and testing. This part, named SVB, can generate not only the standard waveforms to read the full array, but also arbitrary sub-array scan patterns. It can be reprogrammed in seconds, and hold up to four different clocking schemes, which can be selected on a per-integration basis. The SVB is implemented in programmable chips, but, being a conceptual design, can be easily transferred to newer devices.
Inside Fasti there is a central controller for startup, general housekeeping, global control of operations (start integrations for example), data collection, formatting and buffering, or for data preprocessing when needed. In the present design all this is realized with a diskless embedded computer, using an Intel or Alpha family CPU and few commercial boards. The parallel digital acquisition board and the fast Ethernet interface are hosted here.
This part has been custom developed. This section mainly consists of a small number (4 for NICMOS3 and Hawaii) of analog to digital converters and some glue logic. We will use high quality 16 bit converters for the Nics version, and very fast, lower resolution (12 or 14 bits), converters for the Adaptive Optics version.
This part consists mainly of the bias level generation, of digital clocks level shifting and of detector output conditioning. For the Infrared version this part inherits the Nics design, and for LCCD uses a Marconi commercial board.
Fasti has some support software to ease its use and integration in a particular application.
Baffa, C., Comoretto, G., Gennari, S., Lisi, F., Oliva, E., Biliotti, V., Checcucci, A., G., Gavrioussev, V., Giani, E., Ghinassi, F., Hunt, L. K., Maiolino, R., Mannucci, F., Marcucci, G., Sozzi, M., Stefanini, P., Testi, L. 2001, A&A, 378, 722
Baffa, C. 2001, IV Convegno Nazionale di Astronomia Infrarossa, Ciprini, S. ed., Perugia, Italy
Esposito, S., Riccardi, A., Storm, J., Accardo, M., Baffa, C., Biliotti, V., Foppiani, I., Puglisi, A., Ragazzoni, R., Ranfagni, P., Stefanini, P., Salinari, P., Seifert, W., Storm, J. 2002, SPIE Conference AS06, Wizinowich, P. L. Ed., in press
Foppiani, I., Baffa, C., Biliotti, V., Bregoli, G., Cosentino, G, Giani, E., Esposito, S., Marano, B., Salinari, P. 2002, SPIE Conference AS06, Wizinowich, P.L. Ed., in press