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List: usrp-users
Subject: [USRP-users] RFNoC + GNU Radio: spp is set differently
From: "Bachmaier, Luca" <luca.bachmaier () iis ! fraunhofer ! de>
Date: 2023-10-09 14:56:22
Message-ID: 75c7acf9196142a6a2c0fda19fe48938 () iis ! fraunhofer ! de
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Hi all,
I'm currently implementing a GNU Radio flowgraph that makes use of the RFNoC FFT \
block. After fixing a bug found out by Rob Kossler (mail in this mailing list from \
September 14) in the UHD repository, the original problem persists in GNU Radio: \
trying to use FFT lengths greater than 256 throws the error "samples per package must \
not be smaller than atomic item size".
When trying to look closer into the problem I noticed that the spp parameter is set \
differently when using the UHD python API directly (script rfnoc_rx_to_file) and when \
using GNU Radio. I added debug statements to the rfnoc_rx_streamer block that print \
the values of spp and ais.get() (atomic item size). When calling the rfnoc_rx_to_file \
script with a spp set to 1024 and an FFT length of 1024 I get the following output:
[INFO] [0/LogPwr#0] Setting default MTU forward policy.
Using radio 0, channel 0 Attempting to connect FFT:0 to 0/Radio#0:0...
Requesting RX Freq: 0 MHz... Actual RX Freq: 1 MHz...
Waiting for "lo_locked": ++++++++++ locked.
Requesting samples per packet of: 1024
Actual samples per packet = 1024
Using streamer args:
[DEBUG] spp = 18446744073709551615
[DEBUG] ais.get() = 1
[DEBUG] spp = 2000
[DEBUG] ais.get() = 1
[DEBUG] spp = 2000
[DEBUG] ais.get() = 1024
[DEBUG] spp = 1024
[DEBUG] ais.get() = 1024
Since here spp is not smaller than ais.get(), the flowgraph is able to run. When \
trying the same as a GNU Radio flowgraph, the output is the following:
[INFO] [0/LogPwr#0] Setting default MTU forward policy.
[DEBUG] spp = 18446744073709551615
[DEBUG] ais.get() = 1
[DEBUG] spp = 2000
[DEBUG] ais.get() = 1
[DEBUG] spp = 2000
[DEBUG] ais.get() = 2048
[DEBUG] spp = 0
[DEBUG] ais.get() = 2048
For some reason, spp is finally set to zero and ais.get() is set to 2048. I do not \
understand why, and I also don't get why the behavior is different for GNU Radio at \
all. Is it possible that GNU Radio uses its own version of UHD? Up until now I \
believed that GNU Radio simply uses the already installed UHD implementation over the \
UHD Python API. If this is not the case, how can I change this specific GNU Radio UHD \
version? I tried looking into the source code of gnuradio/gr-uhd/lib/rfnoc but I do \
not understand it unfortunately.
Regards
Luca
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<p class="MsoNormal">Hi all,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">I’m currently implementing a GNU Radio \
flowgraph that makes use of the RFNoC FFT block. After fixing a bug found out by Rob \
Kossler (mail in this mailing list from September 14) in the UHD repository, the \
original problem persists in GNU Radio: trying to use FFT lengths greater than 256 \
throws the error “samples per package must not be smaller than atomic item \
size”.<o:p></o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US"><o:p> </o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US">When trying to look closer into the problem I noticed that the spp \
parameter is set differently when using the UHD python API directly (script \
rfnoc_rx_to_file) and when using GNU Radio. I added debug statements to the \
rfnoc_rx_streamer block that print the values of spp and ais.get() (atomic item \
size). When calling the rfnoc_rx_to_file script with a spp set to 1024 and an FFT \
length of 1024 I get the following output:<o:p></o:p></span></p> <p \
class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">[INFO] [0/LogPwr#0] \
Setting default MTU forward policy.<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">Using radio 0, channel 0 Attempting to \
connect FFT:0 to 0/Radio#0:0...<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">Requesting RX Freq: 0 MHz... Actual RX \
Freq: 1 MHz...<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">Waiting for "lo_locked": \
++++++++++ locked.<o:p></o:p></span></p> <p \
class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">Requesting samples \
per packet of: 1024<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">Actual samples per packet = \
1024<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US">Using streamer args:<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] spp = \
18446744073709551615<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] ais.get() = \
1<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US"><o:p> </o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] spp = \
2000<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US">[DEBUG] ais.get() = 1<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] spp = \
2000<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US">[DEBUG] ais.get() = 1024<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] spp = \
1024<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US">[DEBUG] ais.get() = 1024<o:p></o:p></span></p> <p \
class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal"><span lang="EN-US">Since here spp is not smaller than ais.get(), \
the flowgraph is able to run. When trying the same as a GNU Radio flowgraph, the \
output is the following:<o:p></o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US"><o:p> </o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">[INFO] [0/LogPwr#0] Setting default MTU \
forward policy. <br>
<br>
[DEBUG] spp = 18446744073709551615<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] ais.get() \
= 1<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US"><o:p> </o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] spp = \
2000<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US">[DEBUG] ais.get() = 1<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] spp = \
2000<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US">[DEBUG] ais.get() = 2048<o:p></o:p></span></p> <p class="MsoNormal" \
style="margin-left:35.4pt"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">[DEBUG] spp = \
0<o:p></o:p></span></p> <p class="MsoNormal" style="margin-left:35.4pt"><span \
lang="EN-US">[DEBUG] ais.get() = 2048<o:p></o:p></span></p> <p \
class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p> <p \
class="MsoNormal"><span lang="EN-US">For some reason, spp is finally set to zero and \
ais.get() is set to 2048. I do not understand why, and I also don’t get why the \
behavior is different for GNU Radio at all. Is it possible that GNU Radio uses its \
own version of UHD? Up until now I believed that GNU Radio simply uses the already \
installed UHD implementation over the UHD Python API. If this is not the case, how \
can I change this specific GNU Radio UHD version? I tried looking into the source \
code of gnuradio/gr-uhd/lib/rfnoc but I do not understand it \
unfortunately.<o:p></o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US"><o:p> </o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US">Regards<o:p></o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US">Luca<o:p></o:p></span></p> </div>
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