# USRP Handshake **URL:** \ **Category:** GNU Radio\ **Created:** [June 10, 2015, 10:47pm UTC](https://www.ruby-forum.com/t/usrp-handshake/242269 "2015-06-10T22:47:58Z")\ **Posts on this page:** 6\ **Page:** 1
**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:** [June 10, 2015, 10:47pm UTC](https://www.ruby-forum.com/t/usrp-handshake/242269/1 "2015-06-10T22:47:58Z")
Hello everyone, I try to transmitting a file using PSK modulation with 2 x USRP B200 as Tx and Rx. When I run the Tx’s fg, the Tx only transmitted before the Rx fg completely run. But when I run the Rx’s fg, the file sink already write something before I run the Tx’s fg. Is there any way to both Tx and Rx “handshake” before transmission started? – Sincerely, Surya A. University Al Azhar of Indonesia, Jakarta ---
**Author:** ![Surya\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/8e7dd6/32.png) [@Surya\_A](https://www.ruby-forum.com/u/Surya_A)\ **Post date:** [June 10, 2015, 11:56pm UTC](https://www.ruby-forum.com/t/usrp-handshake/242269/2 "2015-06-10T23:56:19Z")
Maybe use a squelch block and wait for for received power to exceed some critical level? Or use timed events? On Wed, Jun 10, 2015 at 1:47 PM, Surya A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Surya A. > University Al Azhar of Indonesia, Jakarta > > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) – GDB has a ‘break’ feature; why doesn’t it have ‘fix’ too? ---
**Author:** ![Surya\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/8e7dd6/32.png) [@Surya\_A](https://www.ruby-forum.com/u/Surya_A)\ **Post date:** [June 11, 2015, 12:17am UTC](https://www.ruby-forum.com/t/usrp-handshake/242269/3 "2015-06-11T00:17:56Z")
Examples of the squelch block include [http://www.ece.uvic.ca/~elec350/grc\_doc/ar01s01s03.html](http://www.ece.uvic.ca/~elec350/grc_doc/ar01s01s03.html) and [http://files.ettus.com/tutorials/labs/Lab\_1-5.pdf](http://files.ettus.com/tutorials/labs/Lab_1-5.pdf) I’ve never used timed events in gnuradio, I just know that you can do things in a time-aligned way. You may want to google for “gnuradio squelch” and “gnuradio timed” Out of curiousity, why do you need to handshake? What’s wrong with a little bit of silence or noise at the beginning and end of your recording? On Wed, Jun 10, 2015 at 3:02 PM, Surya A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > wrote: > > > > > Sincerely, > > Surya A. > University Al Azhar of Indonesia, Jakarta – GDB has a ‘break’ feature; why doesn’t it have ‘fix’ too? ---
**Author:** ![Surya\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/8e7dd6/32.png) [@Surya\_A](https://www.ruby-forum.com/u/Surya_A)\ **Post date:** [June 11, 2015, 11:01am UTC](https://www.ruby-forum.com/t/usrp-handshake/242269/4 "2015-06-11T11:01:42Z")
I want to transmitted digital file (i.e. .jpg) with file source on Tx side then received the file with file sink. It’s not about “silence or noise” because I use access code from packet decoder, the problem is when I start the Rx’s fg the file sink immediately write file output even Tx’s fg not run. Or when I start the Tx’s fg first, the file transmitted (repeat = off) but the Rx’s fg not start yet. I doubt these situation will compromised the output file. I haven’t test it yet, still working to “remove” the noise from transmission. On Thu, Jun 11, 2015 at 5:15 AM, Chris K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > recording? > > > > some critical level? Or use timed events? > > > > > > > completely run. But when I run the Rx’s fg, the file sink already > > > > > > > > * * * > > – > GDB has a ‘break’ feature; why doesn’t it have ‘fix’ too? – Sincerely, Surya A. University Al Azhar of Indonesia, Jakarta ---
**Author:** ![Surya\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/8e7dd6/32.png) [@Surya\_A](https://www.ruby-forum.com/u/Surya_A)\ **Post date:** [June 11, 2015, 11:09am UTC](https://www.ruby-forum.com/t/usrp-handshake/242269/5 "2015-06-11T11:09:53Z")
Hi Surya, > I use access code from packet decoder That sounds like a good approach; you should have told us earlier! > Problem is when I start the Rx’s fg the file sink immediately write > file output even Tx’s fg not run. this means that the access code checking doesn’t work. Best regards, Marcus ---
**Author:** ![Surya\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/8e7dd6/32.png) [@Surya\_A](https://www.ruby-forum.com/u/Surya_A)\ **Post date:** [June 11, 2015, 12:03am UTC](https://www.ruby-forum.com/t/usrp-handshake/242269/6 "2015-06-11T00:03:54Z")
Would you mind to tell me how? I have no idea. On Thu, Jun 11, 2015 at 4:54 AM, Chris K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > completely run. But when I run the Rx’s fg, the file sink already write > > Discuss-gnuradio mailing list > > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) > > – > GDB has a ‘break’ feature; why doesn’t it have ‘fix’ too? – Sincerely, Surya A. University Al Azhar of Indonesia, Jakarta