Re: [Discuss-gnuradio] Need help: How to extract timestamps of data for UHD mimo source block?

[Hongliang Zhang]

Hi Josh,

Thanks so much for your reply. 

I have some questions about the metadata. 

1). I read the codes in the work function. The metadata is defined by:
     uhd::rx_metadata_t metadata;
     
    Does "uhd::rx_metadata_t" define the data type or give values to
metadata?  And in which C++ file may I find that the "uhd::rx_metadata_t" is
created ?

2). Is metadata a scaler or vector? I use 4 USRP2 boards for MIMO receiver
system. Does metadata contain 4 groups of timestamps for each 4 USRP2 boards
or just 1 group of timestamps for the whole synchronised data?

3). When I use the UHD MIMO Source block, GNU Radio Companion shows the
following sentences: 

   Current recv sock buff size: 50000000 bytes
   Current recv sock buff size: 50000000 bytes
   Current recv sock buff size: 50000000 bytes
   Current recv sock buff size: 50000000 bytes
   Using: Flex 2400 MIMO B RX (0x0027)
   Using: Flex 2400 MIMO B TX (0x002b)
   Using: Flex 2400 MIMO B RX (0x0027)
   Using: Flex 2400 MIMO B TX (0x002b)
   Using: Flex 2400 MIMO B RX (0x0027)
   Using: Flex 2400 MIMO B TX (0x002b)
   Using: Flex 2400 MIMO B RX (0x0027)
   Using: Flex 2400 MIMO B TX (0x002b)
   RX samples per packet: 362
   TX samples per packet: 363
   Recv pirate num frames: 33967
   Set time with unknown pps edge:
       1) set times next pps (race condition)
       2) catch seconds rollover at pps edge
       3) set times next pps (synchronously)
   Time was reset successfully on board 1 relative to board 0
   Time was reset successfully on board 2 relative to board 0
   Time was reset successfully on board 3 relative to board 0

Do they mean that 4 boards are synchronised and have the same timestamps? In
which C++ script may I find this sentence :" Time was reset successfully on
board A relative to board B" ? 

Many thanks in advance.

Best wishes,
Hongliang



Josh Blum-2 wrote:
> 
> 
> 
> On 10/06/2010 04:24 AM, Hongliang Zhang wrote:
>>
>> Hi everyone,
>>
>> I set up 4 USRP2 boards for MIMO receiver system for array antennas, and
>> use
>> the PPS signal to synchronise them. I wish to collect the data from the
>> boards as well as the associated timestamps for the four boards.
>>
>> Could someone teach me how to read the time stamps from a UHD mimo source
>> block?  Do I need to modify the block in C++ or Python scripts?
>>
> 
> The timestamps are inside the metadata, they are discarded in the work 
> function: 
> http://gnuradio.org/cgit/gnuradio.git/tree/gr-uhd/lib/uhd_mimo_source.cc?h=next#n127
> 
> You will need to modify the mimo source c++ and find a place to store 
> the timestamps, or write a c++ app that calls into the UHD mimo_usrp 
> interface directly.
> 
> -Josh
> 
>> Thanks so much for every help and suggestions.:clap:
>>
>> Best regards,
>> Hongliang
> 
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> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
> 

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