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Re: [Discuss-gnuradio] not getting timestamps from UHD received stream t
From: |
Josh Blum |
Subject: |
Re: [Discuss-gnuradio] not getting timestamps from UHD received stream tags |
Date: |
Mon, 06 Feb 2012 18:18:37 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111229 Thunderbird/9.0 |
On 02/06/2012 06:13 PM, George Nychis wrote:
> 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":
> https://github.com/gnychis/grforwarder/blob/8f8c4e6cf79a2d635a0eb3bcad9b5ab325f1e373/gr-digital/lib/digital_ofdm_sampler.cc#L78
>
> However, the size of the rx_time tags is consistently zero:
> https://github.com/gnychis/grforwarder/blob/8f8c4e6cf79a2d635a0eb3bcad9b5ab325f1e373/gr-digital/lib/digital_ofdm_sampler.cc#L99
>
> 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).
>
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