UHD Error

GNU Radio
1

Hi,

I am trying to run benchmark_rx.py and the first time I execute it after
booting up the PC, I encounter the error pasted at the end of this
message.
The error goes away when I try to run benchmark_rx again, but comes back
again after rebooting and executing bechmark_rx.
Some information about the PC
~$ uname -a
Linux ubuntu 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan 25
17:13:26
UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.3 LTS
Release: 12.04
Codename: precise

~$ gnuradio-config-info -v
v3.7.0-104-g6bf21a5a

Thanks,
Kapil

Error Message:

~$ /usr/local/share/gnuradio/examples/digital/narrowband/benchmark_rx.py
-m
dbpsk -r 500000 -f 0.6e9 -a addr=192.168.10.2 --spec=A:0 -A TX/RX
–rx-gain=20 -v -S 2
linux; GNU C++ version 4.6.3; Boost_104800; UHD_003.005.001-0-gf3a16983

Using Volk machine: avx_64_mmx

Demodulator:
bits per symbol: 1
RRC roll-off factor: 0.35
FLL bandwidth: 6.28e-02
Timing bandwidth: 6.28e-02
Phase bandwidth: 6.28e-02
– Opening a USRP2/N-Series device…
– Current recv frame size: 1472 bytes
– Current send frame size: 756 bytes

UHD Error:
Control packet attempt 0, sequence number 1:
RuntimeError: no control response, possible packet loss

UHD Error:
Control packet attempt 1, sequence number 2:
RuntimeError: no control response, possible packet loss

UHD Error:
Control packet attempt 2, sequence number 3:
RuntimeError: no control response, possible packet loss
Traceback (most recent call last):
File
“/usr/local/share/gnuradio/examples/digital/narrowband/benchmark_rx.py”,
line 141, in
main()
File
“/usr/local/share/gnuradio/examples/digital/narrowband/benchmark_rx.py”,
line 130, in main
tb = my_top_block(demods[options.modulation], rx_callback, options)
File
“/usr/local/share/gnuradio/examples/digital/narrowband/benchmark_rx.py”,
line 57, in init
options.verbose)
File
“/usr/local/share/gnuradio/examples/digital/narrowband/uhd_interface.py”,
line 190, in init
freq, gain, spec, antenna)
File
“/usr/local/share/gnuradio/examples/digital/narrowband/uhd_interface.py”,
line 52, in init
self.u = uhd.usrp_source(device_addr=args,
stream_args=uhd.stream_args(‘fc32’))
File
“/usr/local/lib/python2.7/dist-packages/gnuradio/uhd/init.py”,
line 121, in constructor_interceptor
return old_constructor(*args)
File
“/usr/local/lib/python2.7/dist-packages/gnuradio/uhd/uhd_swig.py”,
line 1699, in make
return _uhd_swig.usrp_source_make(*args)
RuntimeError: RuntimeError: link dead: timeout waiting for control
packet
ACK

Thanks,
Kapil

2

On 08/23/2013 09:03 PM, Kapil Borle wrote:

Thanks,

– Current send frame size: 756 bytes
Control packet attempt 2, sequence number 3:
File
self.u = uhd.usrp_source(device_addr=args,
packet ACK

Thanks,
Kapil

This may just be an ARP issue. When you first boot, there’s no ARP
cache entry for the USRP, so ARP has to run, and it may be that your IP
stack is
configured to drop packets that arrive at the interface during ARP
negotiation, rather than holding them. Just a guess.

With TCP, this isn’t as big an issue, because TCP has a retry
mechanism. For UDP protocols (which UHD uses) this could be an issue.

3

Hi Marcus,

Adding an entry for the USRP in the arp table indeed solves the problem.
But there is some discrepancy. As far as I know, I can add the entry
using:

  1. ping 192.168.10.2
  2. arp -i eth1 -s 192.168.10.2 {HWADDR}
  3. uhd_find_devices

If I use the 1st method, I run into the same problem, while the later
two
methods work. I have no clue why ping shouldn’t work.

Anyways, thanks for the help.

Kapil

4

two methods work. I have no clue why ping shouldn’t work.

Anyways, thanks for the help.

Kapil

I wonder if your ping command flushes the ARP cache after it’s done?

It would have no reason to do that, by maybe it does?

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium