Hi everybody,
I experience a weird behavior while streaming from my N200 at low sampling
rates.
The setup is as follows: USRP N200 with latest FPGA image, UHD Version
3.14.1.0, Host computer is a Intel NUC Hades Canyon with Ubuntu 18.04 LTS and
CPU governor set to performance. The USRP is directly connected to the NUC (no
switch in between)
If I use the benchmark program at 1 MHz sampling rate, I get multiple sequence
errors, see one example log at the end of this Mail. It does not seem to
correlate with the MTU size: I tried smaller ones and in same cases a smaller
MTU size (about 1000) seems to decrease the number of sequence errors a bit.
The overall CPU load is pretty small. I also experience the same troubles if I
simply stream into a null-sink or any other block in Gnuradio.
If I use a sampling rate of 20MHz or 25MHz I do not get any sequence errors.
And that's what puzzles me: Does anyone have an idea why it works worse at low
sampling rates?
In the manual I found the entry about the ups_per_fifo and ups_per_sec for the
N200 series. However, I did not find more information on that: Would changing
those settings help, and if so, in which direction should I change those
parameters?
Best regards,
Emanuel
xx@xx:/usr/local/lib/uhd/examples$ ./benchmark_rate --duration 600 --rx_subdev
A:A --rx_rate 1e6 --args "addr=192.168.21.2"
[INFO] [UHD] linux; GNU C++ version 8.3.0; Boost_106501;
UHD_3.14.1.HEAD-0-gbfb9c1c7
[00:00:00.000001] Creating the usrp device with: addr=192.168.21.2...
[INFO] [USRP2] Opening a USRP2/N-Series device...
[INFO] [USRP2] Current recv frame size: 1472 bytes
[INFO] [USRP2] Current send frame size: 1472 bytes
[INFO] [USRP2] Detecting internal GPSDO....
[INFO] [GPS] Found an internal GPSDO: Jackson-Labs, FireFly , Firmware Rev 0.929
[INFO] [USRP2] Setting references to the internal GPSDO
Using Device: Single USRP:
Device: USRP2 / N-Series Device
Mboard 0: N200r4
RX Channel: 0
RX DSP: 0
RX Dboard: A
RX Subdev: BasicRX (A)
TX Channel: 0
TX DSP: 0
TX Dboard: A
TX Subdev: Unknown (0xffff) - 0
[00:00:02.491478] Setting device timestamp to 0...
[00:00:02.491698] Testing receive rate 1.000000 Msps on 1 channels
[D00:01:03.889970] Detected Rx sequence error.
[D00:01:28.796795] Detected Rx sequence error.
[D00:01:32.880153] Detected Rx sequence error.
[D00:02:34.087632] Detected Rx sequence error.
[D00:05:13.241379] Detected Rx sequence error.
[D00:06:13.370751] Detected Rx sequence error.
[D00:07:05.771504] Detected Rx sequence error.
[D00:07:12.235087] Detected Rx sequence error.
[D00:08:25.865832] Detected Rx sequence error.
[D00:09:18.883324] Detected Rx sequence error.
[00:10:02.491954] Benchmark complete.
Benchmark rate summary:
Num received samples: 599997347
Num dropped samples: 3630
Num overruns detected: 0
Num transmitted samples: 0
Num sequence errors (Tx): 0
Num sequence errors (Rx): 10
Num underruns detected: 0
Num late commands: 0
Num timeouts (Tx): 0
Num timeouts (Rx): 0
Done!
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