| Rev |
Log message |
Author |
Age |
Path |
| 30 |
Minor documentation edits. |
dgisselq |
3269d 05h |
/dblclockfft/trunk/bench/cpp/ |
| 29 |
Checking in a lot of changes here. These changes were focused on two
things primarily: 1st the ability to match, in bench testing, the bench
test to the configuration of the generated FFT. For this purpose, the
fftgen program now creates fftsize.h and ifftsize.h header files. These
header files contain the parameters that were used in the creation of the
various verilog files, and therefore the C++ test benches may now be compiled
to match the test files. The 2nd change is the multiply. Based upon a
set of slides from Xilinx, I rebuilt my shiftaddmpy into a longbimpy.
(Think if 'bimpy' as a 'bi', or two-bit, 'mpy', or multiply.) Longbimpy
depends upon bimpy, an optimized 2xN bit multiply--optimized for 6-bit
LUTs with carry chains. Longbimpy simply expands that capability to a
NxN bit multiply. Sadly, the longbimpy approach increased my area on the
chip when it was supposed to be a cheaper multiply, so I may well take it
back out in the future. |
dgisselq |
3425d 14h |
/dblclockfft/trunk/bench/cpp/ |
| 28 |
This revision represents a lot of work to get the Verilator simulation to now
match the FPGA performance. The big problem turned out to be in the
bit reversal stage, where a '=' was used on a register instead of a '<='.
Neither Verilator nor Vivado complained, but they each treated the result
differently. In addition, a bug was traced to the soft butterfly, butterfly.v,
whereby the delay through the butterfly did not properly change when the
delay through the multiply changed. All of this has been fixed, and now
appears to work and work well in both hardware and simulation. |
dgisselq |
3435d 08h |
/dblclockfft/trunk/bench/cpp/ |
| 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 15h |
/dblclockfft/trunk/bench/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 05h |
/dblclockfft/trunk/bench/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 08h |
/dblclockfft/trunk/bench/cpp/ |
| 19 |
Added the capability to accumulate bits internal to the FFT, only to drop
those extra bits just before the end. This helps to reduce truncation
error, and may even drop it by a factor of four (my own measurements). |
dgisselq |
3541d 13h |
/dblclockfft/trunk/bench/cpp/ |
| 18 |
This file was placed into the bench/rtl/ directory. |
dgisselq |
3543d 06h |
/dblclockfft/trunk/bench/cpp/ |
| 16 |
Cleaned up the test bench build scripts, made sure license statements were
placed on all files, etc. |
dgisselq |
3543d 06h |
/dblclockfft/trunk/bench/cpp/ |
| 15 |
Added rounding into the routine to remove bias. All of the test benches have
been modified so that the FFT, with rounding, now passes. While the rounding
implementation applied does remove bias, it does not yet remove all bias.
Some work still remains. |
dgisselq |
3544d 04h |
/dblclockfft/trunk/bench/cpp/ |
| 14 |
Found several bugs in the previous version. The biggest were in the qtrstage.
Apparently, the qtrstage didn't work before, even though I thought it did.
Further, the FFT testbench has been adjusted to place proper values into
the fft_tb.dbl file it creates. (I've been testing it by reading this into
Octave, and visually inspecting the results--quantitative testing of the
fft_tb and ifft_tb are still lacking.) Now, however, if I cascade the
forward and reverse together, I seem to get something at least close to the
right answer. Close, of course, is relative. I think all that I still
struggle with is rounding and truncation errors, hence I'm checking in
my changes.
The FFT generator was also modified to allow arbitrary length paths
in the command line specified path prefix. This has not been tested.
A bug was also found in the butterfly, whereby for certain multiply delays
the butterfly would be unable to determine whether or not its results were
valid. Adding an extra bit to the FIFO address in these cases fixed the
problem. This change was encapsulated into the lgdelay() function, and
an additional bflydelay function. In my frustration, I modified the
fftstage function so that, when it is built, the parameters it is built
with are the default parameters. This should only affect testing, by
making any testing more realistic, but that may still remain to be seen.
Another change was made to the core generator, so that now when a core
is generated, the main file now contains a copy of the arguments that were
used when the core generator was invoked. This is good for posterity, in
case you ever need to ask yourself how I ended up here. |
dgisselq |
3545d 03h |
/dblclockfft/trunk/bench/cpp/ |
| 13 |
I updated the butterfly testbench to automatically determine the delay
internal to the chip and multiply, and then to use that delay in determining
whether the values were accurate or not. This is better than the fixed
delay approach that was used before. The change was necessitated by an
attempt to use a different multiply structure that had a different
internal delay to it. (The multiply didn't work out, as it only worked
on operands with identical numbers of bits.) |
dgisselq |
3545d 08h |
/dblclockfft/trunk/bench/cpp/ |
| 9 |
Now working on the test bench for the FFT. Currently, the FFT passes
all test bench "tests." However, the test bench does not yet accurately
report on the success of its work. This remains for future work. Lots
of bugs fixed while making this test bench code work.
(I should mention, while all test benches currently pass, that doesn't
mean that the code works ... yet. I just haven't found the bug that
breaks it.) |
dgisselq |
3551d 08h |
/dblclockfft/trunk/bench/cpp/ |
| 8 |
This completes the initial work on a test bench for the FFT stage. I
chose to test the odd 2048 stage only, but (hopefully) the testbench
will still apply to all other stages as well. At any rate, based upon
some trial runs, it looks like the FFT may be starting to work as well.
More testing is needed, for certain, but to do that I'm going to have
to figure out just what tests are needed, and how exactly to apply those
tests within the test bench construct. |
dgisselq |
3551d 15h |
/dblclockfft/trunk/bench/cpp/ |
| 7 |
Two sources belonging to the last commit, whose comments go with the
last commit, that just didn't make it in time. |
dgisselq |
3552d 02h |
/dblclockfft/trunk/bench/cpp/ |
| 6 |
Lots of work accomplished today. Test benches now exist and work for the:
butterfly, multiply, bitreversal, pairwise FFT stage (dblstage), and the
four-wise FFT stage (qtrstage). Work continues on the single (generic)
FFT stage, and (of course) the FFT isn't ready yet. A second commit will
follow this one shortly with the new files added (oops!--I should've added
them this time--my bad.) |
dgisselq |
3552d 02h |
/dblclockfft/trunk/bench/cpp/ |
| 5 |
The butterfly_tb is now written, and the butterfly succeeds at the test
bench! |
dgisselq |
3552d 09h |
/dblclockfft/trunk/bench/cpp/ |
| 4 |
Bench tests updated, they now state SUCCESS upon successful completion,
return a 0 on success, and all bench tests test all function outputs
(now). |
dgisselq |
3552d 14h |
/dblclockfft/trunk/bench/cpp/ |
| 3 |
The first upload of the s/w didn't take. Had it taken, the comment would've
been: This is the first upload of the double clocked FFT software. While it
should (roughly) be complete, a lot of work remains to be done--primarily
in building test benches, modifying the interface of fftgen to make it
more friendly, etc. In fact, the c++ code not only compiles, but the
Verilog code it produces actually builds as well!
Now, however, I have several test benches written, and have verified the
unit functionality of the multiply, bit reversal stage, the dblstage (FFT
len 2), and the qtrstage (FFT len 4). I then took a closer look at the
multiply, discovered it failed at signed integers and rebuilt it. The
new test bench tests the full 16-bit signed integer support properly. This
leaves butterflies and generic FFT stages that still need test benches, as
does the main (I)FFT program. |
dgisselq |
3552d 15h |
/dblclockfft/trunk/bench/cpp/ |
