© Daniel van der Schuur
In their mission of eliminating all vendor-dependence from the graphical CASPER toolflow, CASPER developers at the South African Radio Astronomy Observatory (SARAO) have been looking into open source alternatives to the current CASPER FPGA processing code (gateware) - among which is the FFT (Fast Fourier Transform), a very important building block in astronomy signal processing.
Over the years, gateware developers at ASTRON created quite a library of reusable (VHDL) building blocks (used in LOFAR and APERTIF), one of which is - you guessed it - an FFT. A very special kind of FFT in fact; it is designed to work in applications where the sample clock is higher than the FPGA processing clock (the clock factor is shown as P in the top left figure). And as VHDL is a text based description of gateware, is it more portable than graphical gateware representations.
SARAO has recently ported this ASTRON wideband FFT to the CASPER toolflow, with initial results looking promising. SARAO not only reused the ASTRON FFT, but made several improvements and additions along the way, which will be backported to the ASTRON FFT hosted on OpenCores.org.
This is a great example of how open source gateware benefits not only those (re)using it, but also those who initially created it. Open source code (if sufficiently exposed) evolves over time, stimulating collaboration and exchange of expertise, allowing developers worldwide to reduce the time to science.