On 04/22/2019 11:37 AM, Rob Kossler wrote:
Marcus & Ettus folks,
I just experienced a similar issue using gnuradio with the example
rfnoc_fosphor program (the issue being that the frequency I request is
not what I get). This seems to me to be a pretty significant bug.
While playing with rfnoc_fosphor, I fiddled with the Cordic Freq param
of the DDC a bit. Then, I set this parameter back to zero and ran
multiple consecutive runs without changing any params. My setup had a
center freq of 2450MHz, DDC rate of 100 MHz, and I had a 2450MHz
antenna connected directly to the X310/UBX160 input (dboard B,
Tx/Rx). I was simply monitoring all the energy in the ISM band
2400-2480 MHz (this band has lots of energy in my environment, but
outside this span it is pretty quiet).
I ran 7 iterations (consecutive runs) without changing params and I
expected to see energy from 2400-2480. In each run, I saw the energy,
but the frequency shown often did not represent reality. Note: the
"????" below denotes that the location was off-display (presumably 80
MHz from the other endpoint).
- run 1: energy located (2475-???? MHz)
- run 2: energy located (2400-2480 MHz) (as expected)
- run 3: energy located (2435-???? MHz)
- run 4: energy completely off-display (> 2500 MHz)
- run 5: energy located (2400-2480 MHz) (as expected)
- run 6: energy located (????-2467 MHz)
- run 7: energy located (2400-2480 MHz) (as expected)
I captured screenshots of each and would be glad to provide them to
anyone interested. I also have the gnuradio rfnoc_foshphor python
script if anyone is interested.
I recognize that it is not easy to duplicate the above results because
it requires an FPGA image with specific blocks that support fosphor.
However, I want to mention that all of the blocks in the experiment
above are non-modified "stock" blocks. The C++ program I attached to
the original post provides a way to duplicate this issue with the
standard FPGA image.
Rob
So, to be clear, this happens *after* you've specified a non-zero DDC
offset, and THEN revert to a zero DDC offset? Also, are you still using
timed
commands for tuning? Trying to tease-apart the possible areas to
look at.
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
