[USRP-users] time sync 2 ettus x310

Sanjoy Basak sanjoybasak14 at gmail.com
Wed Apr 22 05:36:29 EDT 2015


Dear Mr. Michael,
Thank you very much for the reply. I am putting all the information here
regarding usrp.

daughter board: SBX-120
UHD version: UHD_003.008.002-80-ge28d7844

I am attaching here a pdf which includes all other information of the usrp.
Please send me the patch and other instruction and suggestion.
Have a nice day.

best regards
Sanjoy


On Wed, Apr 22, 2015 at 2:29 AM, Michael West <michael.west at ettus.com>
wrote:

> Hi Sanjoy,
>
> The distortion may be due to the fact that some frontend components are
> disabled or powered down while not transmitting or receiving and take a
> little time to settle when enabled or powered up.  For the X310, there are
> 3 ways around this:
>
> 1)  Start TX and RX earlier and throw away RX data (as you have done)
> 2)  Modify ATR settings dynamically so the frontend components stay
> powered on and enabled.  This can be done by using the
> multi_usrp::set_gpio_attr() method.  The banks are RX0, RX1, TX0, and TX1.
> You can accomplish this by adding the following lines to your code:
>     usrp->set_gpio_attr("RX0", "ATR_0X", usrp->get_gpio_attr("RX0",
> "ATR_XX", 0), ~0, 0);
>     usrp->set_gpio_attr("RX1", "ATR_0X", usrp->get_gpio_attr("RX1",
> "ATR_XX", 0), ~0, 0);
>     usrp->set_gpio_attr("TX0", "ATR_0X", usrp->get_gpio_attr("TX0",
> "ATR_XX", 0), ~0, 0);
>     usrp->set_gpio_attr("TX1", "ATR_0X", usrp->get_gpio_attr("TX1",
> "ATR_XX", 0), ~0, 0);
>     usrp->set_gpio_attr("RX0", "ATR_0X", usrp->get_gpio_attr("RX0",
> "ATR_XX", 1), ~0, 1);
>     usrp->set_gpio_attr("RX1", "ATR_0X", usrp->get_gpio_attr("RX1",
> "ATR_XX", 1), ~0, 1);
>     usrp->set_gpio_attr("TX0", "ATR_0X", usrp->get_gpio_attr("TX0",
> "ATR_XX", 1), ~0, 1);
>     usrp->set_gpio_attr("TX1", "ATR_0X", usrp->get_gpio_attr("TX1",
> "ATR_XX", 1), ~0, 1);
> *Note that changing the antenna or gain settings may overwrite these
> values.
> 3)  Modify ATR settings in UHD code.  This is done by editing the UHD code
> for the specific daughter board to change the ATR settings.
>
> Option #3 is the one that has worked the best for most users.  If you let
> me know what daughter card and UHD version you are using, I may be able to
> provide you with a UHD patch.
>
> Regards,
> Michael
>
>
>
> On Tue, Apr 21, 2015 at 1:34 AM, Sanjoy Basak via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>
>> Dear Mr. Martin,
>> Thanks for the reply. Yes, right now I am not using octoclock, so the
>> problem while using 2 USRPsis understandable.
>>
>> However, regarding distortion, yes I am having distortion at the
>> beginning when I am using one usrp  for SISO case for x310. I found this
>> problem even in b210 as well. I wonder why no one discussed or how did they
>> actually solved for radar uses. But I hope I would get my solution here.
>>
>>
>> [image: Inline image 1]
>> This is a figure of xcorr of rx and tx signal. The red marked distortion
>> I am having almost always. I don't know the reason. If I drop few bins in
>> my binary file and then start receiving my signal then I am getting an
>> undistorted signal looks like the following.( I am transmitting and
>> receiving using binary file).
>> However, dropping bins is undesirable for radar application.
>> [image: Inline image 3]
>> If I use the distorted frame, as obvious I get distorted result. However,
>> after dropping bins the fresh frame gives me the exact result after signal
>> processing in matlab.
>> Can you please tell me how to avoid this distortion at the beginning?
>>
>> best regards
>> Sanjoy
>>
>>
>>
>>
>>
>>
>>
>>
>> On Tue, Apr 21, 2015 at 12:10 AM, Martin Braun via USRP-users <
>> usrp-users at lists.ettus.com> wrote:
>>
>>> Sanjoy,
>>>
>>> if you want to do radar, you need to make sure both devices are
>>> connected to the same external reference. For radar, you can't run off
>>> of separate clocks.
>>>
>>> We've confirmed timing accuracy across devices on the nanosecond scale
>>> in the past (using OctoClocks for clock distribution).
>>>
>>> Cheers,
>>> M
>>>
>>> On 17.04.2015 06:00, Sanjoy Basak via USRP-users wrote:
>>> > Hi all,
>>> > I am trying to sync 2 ettus x310 in time. However, I am always having a
>>> > distortion at the beginning after receiving, and there is always a
>>> > delay of few microseconds between the tx and rx. I put tx in one x310
>>> > and rx in another x310 and its in a wired connection. GPS antenna is
>>> > connected to one usrp(with Tx) and another one is on external ref(Rx).
>>> >
>>> > So now if I check the last pps on both usrp; it shows tx:0; rx:2s;
>>> > then I am compensating it making it set_start_time both at for 4s. So
>>> > ideally I should get time synced tx and rx signal.
>>> >
>>> > But I am getting distortion in Rx signal for 2seconds at the beginning;
>>> > this is constant for every sampling freq; so if in that region I have
>>> my
>>> > rx signal I can't retrieve that as the distortion is already introduced
>>> > there.
>>> > As I am trying to implement radar with x310, this is a serious problem
>>> > for me. As within first 2 seconds and few microseconds I can't receive
>>> > anything.
>>> >
>>> > I would really appreciate any kind of suggestion that come through. If
>>> > anyone have question regarding setup or python code please ask.
>>> > Thanks for reading.
>>> >
>>> > Best regards
>>> > Sanjoy
>>> >
>>> >
>>> >
>>> > _______________________________________________
>>> > USRP-users mailing list
>>> > USRP-users at lists.ettus.com
>>> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>> >
>>>
>>>
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com
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>>>
>>
>>
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>>
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