[Discuss-gnuradio] About sample lost

[Zan Li]

Dear list,
Now I meet a problem about counting all the input samples.  I hope I can
get some assistant from here. The problems are as follows,
In one of my blocks, I want to count all the consumed input samples to get
the timestamp of the received packet. I have used GPS to synchronize two
usrps and therefore for the same packet the two usrp should consume the
same amount of samples in this block from the beginning of the stream. At
the very beginning, it works fine but after it works for a while the
timestamp in one usrp will lost 8192 samples (8192 samples less than the
other one). I have checked it is the same as the maximum output buffer of
one block.

I want to ask if it is possible that because the block can not process the
sample as fast as the output from the previous block, one buffer of samples
are lost. BTW I did not find any indicator of overflow from uhd when I run
the code.

Any suggestions would be appreciated.

Best regards

Zan
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[Discuss-gnuradio] about gps lock

[Zan Li]

Dear all,
I meet a problem about the gpsdo for lock. First I check the
usrp->get_mboard_sensor("gps_locked",0); it indicates the gps is locked.
Then the program is sleep for 5 mins. Then I check the gps again but in
this time it does not lock. I do not think that in this 5 mins the gps lost
lock because every time I try like this, the first time it is locked but
after 5 mins it is unlocked, as follows:


*The reference clock is:GPS lock status: locked*
Setting device clock source to:external
Setting device clock rate to:1e+08
Setting time source to:external
*The reference clock is:GPS lock status: unlocked*

UHD Warning:
get_time: ValueError: get_nmea(): no GPRMC message found

UHD Warning:
get_time: ValueError: get_nmea(): no GPRMC message found
*(Here I can not read the gps time from the gpsdo, I think it is because
the gpsdo does not lock).*

Does anybody meet the similar problem? Any suggestion would be appreciated.

Best regards

Zan
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Re: [Discuss-gnuradio] about gps lock

[Zan Li]

I have done more tests about the gps message.
while(1){
sleep(1);
std::cout << usrp->get_mboard_sensor("gps_gprmc",0).to_pp_string()
<< std::endl;
}

For the output, at the beginning, there are gps_gprmc message outputs but
after it runs for a while, there would be no gps_gprmc message output. If I
restart, it also works at the beginning. (I update the uhd to 003.005.003
and it works like that. For the old version (003.005.001) I did not meet
this problem.) Does somebody know why it is? thanks!

Best regards

Zan

2013/6/10 Zan Li 

> Hi Marcus,
> We have extend the antenna out to the windows and there is an adequate
> view of sky. When I use the uhd UHD_003.005.001, there is no such problem
> but now I upadate the version to UHD_003.005.003.
>
> Best regards
>
> Zan
>
>
> 2013/6/8 Marcus D. Leech 
>
> **
>>
>>Dear all,
>>  I meet a problem about the gpsdo for lock. First I check the
>> usrp->get_mboard_sensor("gps_locked",0); it indicates the gps is locked.
>> Then the program is sleep for 5 mins. Then I check the gps again but in
>> this time it does not lock. I do not think that in this 5 mins the gps lost
>> lock because every time I try like this, the first time it is locked but
>> after 5 mins it is unlocked, as follows:
>>
>>
>> *The reference clock is:GPS lock status: locked*
>> Setting device clock source to:external
>> Setting device clock rate to:1e+08
>> Setting time source to:external
>> *The reference clock is:GPS lock status: unlocked*
>>
>> UHD Warning:
>> get_time: ValueError: get_nmea(): no GPRMC message found
>>
>> UHD Warning:
>> get_time: ValueError: get_nmea(): no GPRMC message found
>>  *(Here I can not read the gps time from the gpsdo, I think it is
>> because the gpsdo does not lock).*
>>
>>  Does anybody meet the similar problem? Any suggestion would be
>> appreciated.
>>
>>  Best regards
>>
>>  Zan
>>
>>
>> ___
>> Discuss-gnuradio mailing 
>> listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>  So, I will ask an obvious question:
>>
>> Does your GPS receiver have an adequate view of the sky?  That is, does
>> it have an external, amplified antenna outdoors, or near a window that
>> doesn't
>>   have low-E film on it.
>>
>>
>>
>> --
>> Marcus Leech
>> Principal Investigator
>> Shirleys Bay Radio Astronomy Consortiumhttp://www.sbrac.org
>>
>>
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>>
>
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