# Connect Digital In with Digital Out in RT Box

**URL:** <https://forum.plexim.com/t/connect-digital-in-with-digital-out-in-rt-box/733>\
**Category:** RT Box\
**Tags:** plecs, rt-box\
**Created:** [January 20, 2020, 10:05am UTC](https://forum.plexim.com/t/connect-digital-in-with-digital-out-in-rt-box/733 "2020-01-20T10:05:01Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Rojitas](https://avatars.discourse-cdn.com/v4/letter/r/b5a626/32.png) [@Rojitas](https://forum.plexim.com/u/Rojitas)\
**Post date:** [January 20, 2020, 10:05am UTC](https://forum.plexim.com/t/connect-digital-in-with-digital-out-in-rt-box/733/1 "2020-01-20T10:05:01Z")

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It is possible to connect the digital outputs with the digital inputs on the rt box internally by software? or Is necessary a loopback cable?

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**Author:** ![Bryan\_Lieblick](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/bryan_lieblick/32/10_2.png) [@Bryan\_Lieblick](https://forum.plexim.com/u/Bryan_Lieblick)\
**Post date:** [January 21, 2020, 10:22am UTC](https://forum.plexim.com/t/connect-digital-in-with-digital-out-in-rt-box/733/2 "2020-01-21T10:22:55Z")

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There is no means to “internally” connect the digital outputs and digital inputs. You can always use the input signal to the Digital Output component elsewhere in the PLECS model, but this approach isn’t suitable for PWM Output and PWM Capture since it bypasses the RT Box FPGA fabric.

You will have to loopback the signal through a physical connection. You can use a male-to-female DSUB-37 cable to loopback all digital I/O signals, the RT Box breakout boards along with a jumper across the digital I/O pins, or some other kind of wiring approach.