# How to TX burst data from file, at specified time

**URL:** <https://www.ruby-forum.com/t/how-to-tx-burst-data-from-file-at-specified-time/237233>\
**Category:** GNU Radio\
**Created:** [October 30, 2013, 10:55pm UTC](https://www.ruby-forum.com/t/how-to-tx-burst-data-from-file-at-specified-time/237233 "2013-10-30T22:55:41Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [October 30, 2013, 10:55pm UTC](https://www.ruby-forum.com/t/how-to-tx-burst-data-from-file-at-specified-time/237233/1 "2013-10-30T22:55:41Z")

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I would like to receive a suggestions of yours on which is the simplest  
way to transmit a burst of data, at specific time, using USRP N210. I  
am planning to input 1pps & 10 MHz to the USRP, in order to have the  
start of burst accurately synchronized to the external 1pps (for me  
accurately means with a jitter of less than about 100 ns).

I saw that there are some examples in the UHD and GR documentation, but  
I wasn’t able to understand how to use them. Please consider that,  
until now, I am able to design a system using GRC, I am just able to  
create my own GR block (I just followed the example on how to create an  
out-of-tree module), but I am not able to do any more.

Is there any way to design what I need using just GRC? No one created  
such a block in GRC?

Best regards

Piero

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**Author:** ![i0kpt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/96bed5/32.png) [@i0kpt](https://www.ruby-forum.com/u/i0kpt)\
**Post date:** [November 1, 2013, 12:35am UTC](https://www.ruby-forum.com/t/how-to-tx-burst-data-from-file-at-specified-time/237233/2 "2013-11-01T00:35:32Z")

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Perhaps the solution to my question could be a code modification of one  
of the following examples:

uhd/host/examples/tx\_samples\_from\_file.cpp  
and  
uhd/host/examples/tx\_timed\_samples.cpp

in order to start a transmission of a burst, got from a file, exactly at  
the 1pps pulse.

Could some one suggests how modify the above example codes?

Regards

Piero