# LimeSDR USB connecting proble..Falshing LEDs

**URL:** <https://discourse.myriadrf.org/t/limesdr-usb-connecting-proble-falshing-leds/5358>\
**Category:** General Discussion\
**Created:** [15 November 2019 16:42 UTC](https://discourse.myriadrf.org/t/limesdr-usb-connecting-proble-falshing-leds/5358 "2019-11-15T16:42:28Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![Zack](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/zack/32/89_2.png) [@Zack](https://discourse.myriadrf.org/u/Zack)\
**Post date:** [7 October 2020 07:02 UTC](https://discourse.myriadrf.org/t/limesdr-usb-connecting-proble-falshing-leds/5358/12 "2020-10-07T07:02:00Z")

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> [@Mohammad](#):
>
> The goal is this when SDR sending a pulse in0.5-3.5 GHz one of the port of the switch well be open and the rest are off, and after receiving the signals we open the next one port and so on.

To implement this functionality you have to modify FPGA gateware. LimeSDR-USB got 8 GPIOs you may use for switch control.

Another solution may be to utilize what is implemented in FPGA gateware 2.23 version already. FPGA\_GPIO0 (J22, Pin 1) is used to indicate when data are being transmitted (high level indicates data transmition is active). To activate this you have to write to FPGA register 0x00C0 value 0xFFFE. Then feed this signal to Arduino and you will know when signal is being transmitted.  
Hope this helps.

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