# GPIO pin changing output when TX stream starts

**URL:** <https://discourse.myriadrf.org/t/gpio-pin-changing-output-when-tx-stream-starts/3113>\
**Category:** LimeSDR\
**Created:** [4 August 2018 23:49 UTC](https://discourse.myriadrf.org/t/gpio-pin-changing-output-when-tx-stream-starts/3113 "2018-08-04T23:49:26Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![OCB](https://avatars.discourse-cdn.com/v4/letter/o/f14d63/32.png) [@OCB](https://discourse.myriadrf.org/u/OCB)\
**Post date:** [4 August 2018 23:49 UTC](https://discourse.myriadrf.org/t/gpio-pin-changing-output-when-tx-stream-starts/3113/1 "2018-08-04T23:49:26Z")

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Good evening,

I was wondering if there is any simple way of modifying the FPGA gateware so that when the TX stream starts, a GPIO pin is set to high, for instance. The reason is to have more control over the starting of a transmitting stream, in order to synchronize the LimeSDR with other devices. I’m a complete newbie to FPGA programming and diving in its code looks terrifying.

Thanks in advance!

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**Author:** ![ccsh](https://avatars.discourse-cdn.com/v4/letter/c/3be4f8/32.png) [@ccsh](https://discourse.myriadrf.org/u/ccsh)\
**Post date:** [5 August 2018 00:15 UTC](https://discourse.myriadrf.org/t/gpio-pin-changing-output-when-tx-stream-starts/3113/2 "2018-08-05T00:15:49Z")

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It feels like such feature has [already been implemented](https://github.com/myriadrf/LimeSuite/issues/149#issuecomment-352750275) at some point, but I am not sure if it is still present in current release of LimeSuite.

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**Author:** ![Kc7noa](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/kc7noa/32/144_2.png) [@Kc7noa](https://discourse.myriadrf.org/u/Kc7noa)\
**Post date:** [6 November 2018 04:40 UTC](https://discourse.myriadrf.org/t/gpio-pin-changing-output-when-tx-stream-starts/3113/3 "2018-11-06T04:40:04Z")

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Not every one uses LimeSuite for rx or tx … i use SdrAngel