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[/] [dblclockfft/] [trunk/] [bench/] [cpp/] [hwbfly_tb.cpp] - Rev 29

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26 A lot of updates and upgrades in this release. Specifically, work took place
over the last several days to demonstrate this FFT on an FPGA. It was
demonstrated on the Xilinx Artix-7 found on a Basys-3 development board.
Part of the effort stemmed around making certain that the DSPs were used
optimally, part of it stemmed around making certain that various parts of the
FFT could use block RAM-type memories. The other massive change involved
removing as much unnecessary logic as possible, so that two 16-bit 1k FFTs
could fit onto this part--together with other glue logic. The bottom line,
though, is that it all now works. Specifically, I've tested it successfully
with

fftgen -f <FFTSIZE> -n 16 -m 16 -p 7 -c 1 -x 1

and with FFTSIZEs of 32, 64, 128, 256, 512, and 1024.

Oh, I should mention that there's also an undocumented DEBUG interface to the
part, and I fixed where the Verilog files went when given an argument, so
that they actually went to the directory specified. Minor updates have taken
place to the documentation format, making it match the documentation format
for other opencores projects that I've produced.

On a sadder note, the Verilator simulation fft_tb no longer works. (Yeah, get
that---the FFT implementation works but Verilator does not. Sigh).		 dgisselq 3457d 13h /dblclockfft/trunk/bench/cpp/hwbfly_tb.cpp
23 Lot's of work to implement a variable means of rounding. The variable
rounding is now implemented within the code, all that's left is to
place a command line option to the generator to choose how values
are to be rounded: either by truncation (drop the lower bits), by
always rounding half up (if the first extra bit is one, go up),
by rounding away from zero (if exactly .5, move away from zero), or
by rounding towards even (if exactly .5, move towards the nearest
even value).

This added an extra clock cycle to each stage, so all of the
test benches needed to be reworked. There is currently no testbench
to test the rounding method itself. This necessitated some
wholescale changes to the testbench code, and the addition
of the twoc.[h|cpp] files. (They were within every piece of code, just
copied from one to the next, this now encapsulates them within their
own file so fixes will propagate to all.) Other changes include creating
testbench classes, adjusting the classes so that one can test what will
happen if the sync isn't added initially, and more. In the end, my
problem was tied to an assumption within fftmain.v that dblstage would
always be a one tick delay, whereas with the one tick of the rounding
function it now becomes a two tick delay .... but the task is done, and
the FFT appears to work again. The maximum sum of square errors (XISQ)
is about half what it was before now, when I use convergent rounding.		 dgisselq 3537d 04h /dblclockfft/trunk/bench/cpp/hwbfly_tb.cpp
22 Lot's of changes, mostly around getting this multiply to fit within a
particular FPGA. Specifically, we just added the capability of using
hardware multiplies to the command line options. Use them if you have
them, and it will simplify the operation of the FFT.		 dgisselq 3538d 07h /dblclockfft/trunk/bench/cpp/hwbfly_tb.cpp

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