# External mode connection failed in RT-BOX based test

**URL:** <https://forum.plexim.com/t/external-mode-connection-failed-in-rt-box-based-test/807>\
**Category:** RT Box\
**Tags:** rt-box, c2000\
**Created:** [July 19, 2020, 10:12am UTC](https://forum.plexim.com/t/external-mode-connection-failed-in-rt-box-based-test/807 "2020-07-19T10:12:32Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![shichenseu](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@shichenseu](https://forum.plexim.com/u/shichenseu)\
**Post date:** [July 19, 2020, 10:12am UTC](https://forum.plexim.com/t/external-mode-connection-failed-in-rt-box-based-test/807/1 "2020-07-19T10:12:32Z")

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I am downloading c2000 tutorial 2 ,namely the ‘PWM Output’ example and I want to use the external mode,but the error message occured and I can’t connect the 28335 development board with the PC.Can anyone help me ?

 ![191](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/35d61c9122eff7557c40c4d203b3ddb27a7ae367.jpeg)

Do I need to change the setting of SCI?

 ![191](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/f8bdfe7d7bbfe18d83636a3fc2926c03d74e6cc4.jpeg)

 ![191](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/3b9baf9f281ac44b7492b7005cf8accd623c22c4.jpeg)

And I wonder whether I have enough equipments for the communication between the PC and 28335 development board

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**Author:** ![Manu\_Parimi](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/manu_parimi/32/6_2.png) [@Manu\_Parimi](https://forum.plexim.com/u/Manu_Parimi)\
**Post date:** [July 20, 2020, 2:24pm UTC](https://forum.plexim.com/t/external-mode-connection-failed-in-rt-box-based-test/807/2 "2020-07-20T14:24:12Z")

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Hi,

I think this question is best suited for Plexim support. Could you please email your question to [support@plexim.com](mailto:support@plexim.com)?

Thanks,  
Manu