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

> 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 ?
>

http://www.ettus.com/uhd_docs/doxygen/html/structuhd_1_1rx__metadata__t.html

> 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?
>

"scalar" that is 1 metadata struct for all N aligned channels.

> 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 1 relative to board 0" ?
>

Yes, it means that all N boards have the same time in their time
registers. The code here:

http://ettus-apps.sourcerepo.com/redmine/ettus/projects/uhd/repository/revisions/master/entry/host/lib/usrp/mimo_usrp.cpp#L116

I cannot say where "Time was reset" is in the code, I am surprised to
see those last 3 lines.

-Josh

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