Not getting timestamps from UHD received stream tags

I am trying to read incoming RX timestamps from the UHD sample stream.
I’d
like to calculate the approximate time a preamble is received in the
OFDM
code.

The issue is that, despite getting incoming frames and preambles, I do
not
seem to be getting timestamp values. I use get_tags_in_range() on
“rx_time”:

However, the size of the rx_time tags is consistently zero:

The output of the OFDM receiver code:
ok: True pktno: 637 n_rcvd: 18 n_right: 17
got a preamble, size of time_tags: 0
ok: True pktno: 638 n_rcvd: 19 n_right: 18
got a preamble, size of time_tags: 0
ok: True pktno: 639 n_rcvd: 20 n_right: 19
got a preamble, size of time_tags: 0

Is there something I am missing to enable the RX timestamp on the
incoming
samples, or am I not properly reading the stream tag? My branch came
from
the GR master 4 days ago (309ca769af).

Thanks a bunch.

  • George

On 02/06/2012 06:13 PM, George N. wrote:

https://github.com/gnychis/grforwarder/blob/8f8c4e6cf79a2d635a0eb3bcad9b5ab325f1e373/gr-digital/lib/digital_ofdm_sampler.cc#L99

Is there something I am missing to enable the RX timestamp on the incoming
samples, or am I not properly reading the stream tag? My branch came from
the GR master 4 days ago (309ca769af).

The timestamps are only sent on the very first packet and after overflow
conditions. Are you seeing at least one tag at the very beginning of
streaming?

-Josh

Bingo, didn’t realize they were only incoming at those points in time.
Problem solved, thanks Josh!

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