Can not get rx time tags

Hi,
I’m trying to get rx time tags in narrowband Benchmark_tx/rx with a
modified digital_correlate_access_code.cc. But the
“get_tags_in_range(rx_time_tags,0,this->nitems_read(0)+i,this->nitems_read(0)+i+1,pmt::pmt_string_to_symbol(“rx_time”))”

method gets no tag in rx_time_tags while the communication between two
USRP N210s running benchmark_rx/tx is OK.
I’m using GNU Radio 3.6.5.1, Ubuntu12.04, boost 1.48 and UHD 3.5.3.
Thanks in advance.

On 09/03/2013 12:41 AM, Harry Z. wrote:

Hi,
I’m trying to get rx time tags in narrowband Benchmark_tx/rx with a
modified digital_correlate_access_code.cc. But the

“get_tags_in_range(rx_time_tags,0,this->nitems_read(0)+i,this->nitems_read(0)+i+1,pmt::pmt_string_to_symbol(“rx_time”))”

method gets no tag in rx_time_tags while the communication between two
USRP N210s running benchmark_rx/tx is OK.
I’m using GNU Radio 3.6.5.1, Ubuntu12.04, boost 1.48 and UHD 3.5.3.
Thanks in advance.

The time tag is sent once at the beginning of streaming and after
overflows. Its not necessary to send more time tags because the absolute
sample count and sample rate can be used to interpolate the time to any
sample.

So I think are you seeing a time tag, just only once at init time. When
the block sees the time, try to save the timestamp and the count it was
found at.

I hope that helps!
-josh

Dear Josh,
Thanks for your reply.
I move the code “get_tags_in_range” in
digital_correlate_access_code, so it will be executed when
digital_correlate_access_code runs.
I start the sender first and then the receiver. But I still get no
tag.
Does “the beginning of stream” mean the point just the receive program
runs?

2013/9/5 Josh B. [email protected]:

On 09/06/2013 08:08 PM, Gong Z. wrote:

Dear Josh,
Thanks for your reply.
I move the code “get_tags_in_range” in
digital_correlate_access_code, so it will be executed when
digital_correlate_access_code runs.
I start the sender first and then the receiver. But I still get no tag.
Does “the beginning of stream” mean the point just the receive program runs?

Well, when the USRP source block begins streaming, the very first sample
should have a time tag.

What blocks are in between USRP source and digital correlate access
code? The reason I ask, is that some block in the middle may not be
propagating tags. Which would explain the missing tags :slight_smile:

-josh

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