[USRP-users] N210 Stops Transmitting

Liwei xieliwei+usrp at gmail.com
Sat Oct 18 08:43:55 EDT 2014

Hi Marcus,
    Thanks for the reply. I guess it is likely that the network
interfaces I've tried are buggy. Here's what you've asked for:
        01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 07)
    I've also tried one of those new USB3 ethernet adapters (seeing
that the laptop only has fast ethernet):
        Bus 004 Device 013: ID 0b95:1790 ASIX Electronics Corp.
    And out of desperation, Wi-Fi:
        02:00.0 Network controller: Qualcomm Atheros AR9485 Wireless
Network Adapter (rev 01)
    I'm going to try a different linux distribution today.


On 18 October 2014 19:49, Marcus Müller <usrp-users at lists.ettus.com> wrote:
> Hi Liwei,
> "SU" is bad, because
> "U" stands for underflow, which means the USRP hasn't gotten enough
> samples in time and ran out of things to transmit.
> The "S" represents a sequence error, which can only happen if for some
> reason network packets got lost or reordered.
> I haven't seen these errors very often, and in the few cases, it was due
> to either a heavily underpowered PC, being so busy with signal
> processing that the kernel just had to drop network packets, or due to a
> horribly buggy network card, but you seem to achieve reasonable
> throughput, so I'm a bit out of ideas here. Nevertheless, could you
> share what
> "lscpi|grep -i ethernet"
> tells you?
> Greetings,
> Marcus
> On 18.10.2014 12:06, Liwei via USRP-users wrote:
>> Hello list,
>>     Anyone with any suggestions? I understand that a "U" in the debug
>> output indicates an underflow, but am not sure why that should cause
>> gnuradio to stop sending samples.
>> Thanks
>> On 9 October 2014 01:10, Liwei <xieliwei+usrp at gmail.com> wrote:
>>> Hello list,
>>>     This may have been asked before (I vaguely remember seeing an
>>> email with a similar issue some time back), but what causes UHD to
>>> stop sending transmission packets to an N210?
>>>     With a simple flowgraph [signal source] -> [uhd sink] at 200k
>>> sample rate over gigabit ethernet, I get up to about 3 seconds of
>>> transmission before everything suddenly goes silent.
>>>     Here's what I see logged:
>>> linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.007.002-107-g0ca4b4f8
>>> -- Opening a USRP2/N-Series device...
>>> -- Current recv frame size: 1472 bytes
>>> -- Current send frame size: 1472 bytes
>>> SU
>>>     Nothing else after "SU".
>>>     Interestingly, if I add a receive + fft chain in the same
>>> flowgraph, the receive stream works fine even after the transmission
>>> has stopped. In fact, if I loop the TX and RX ports on the N210
>>> together (with an attenuator in between) I can see, in the received
>>> signal fft, the frequency peak for the few seconds the N210 is able to
>>> transmit.
>>>     Gqrx also works well receiving FM radio stations all the way up to
>>> about 10MHz sampling rate, after which samples start to get dropped.
>>>     I'm running on a fresh install of Ubuntu 14.04, with everything
>>> installed using pyBOMBS. I've tried switching to yesterday's 3.7.3
>>> maint branch but no difference. Firmware and FPGA image were updated
>>> after each version switch.
>>>     Attached is a screenshot in Wireshark showing the sudden
>>> transmission stop. Note that only packets originating from the
>>> computer is shown.
>>>     Also attached is the output from uhd_usrp_probe.
>>>     $ uname -a
>>> Linux Ubuntu 3.15.0-031500rc2-generic #201404201435 SMP Sun Apr 20
>>> 18:36:18 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
>>>     It may be due to a buggy ethernet adapter, but I've achieved over
>>> 900MBits/s for both TX and RX over iperf. I've also tried another Fast
>>> (instead of gigabit) ethernet adapter and even Wi-Fi, but no
>>> difference. There is currently a Dell managed switch in-between the
>>> computer and N210, but I've tried directly connecting both together
>>> with no difference in results either.
>>>     Also, the current setup works flawlessly with a B210 which I have on hand.
>>>     At this point, any hint would be great!
>>> Thanks
>>> Liwei
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