# Signal mismatch between RT Box Analog Out and DSP ADC in external mode

**URL:** <https://forum.plexim.com/t/signal-mismatch-between-rt-box-analog-out-and-dsp-adc-in-external-mode/2998>\
**Category:** General\
**Tags:** plecs, rt-box, c2000\
**Created:** [April 15, 2026, 1:35pm UTC](https://forum.plexim.com/t/signal-mismatch-between-rt-box-analog-out-and-dsp-adc-in-external-mode/2998 "2026-04-15T13:35:13Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Seoyoung](https://avatars.discourse-cdn.com/v4/letter/s/ecae2f/32.png) [@Seoyoung](https://forum.plexim.com/u/Seoyoung)\
**Post date:** [April 15, 2026, 1:35pm UTC](https://forum.plexim.com/t/signal-mismatch-between-rt-box-analog-out-and-dsp-adc-in-external-mode/2998/1 "2026-04-15T13:35:13Z")

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Hello everyone,

I am currently working on a project using PLECS together with a DSP-based controller, and I am experiencing a signal mismatch issue in external mode. In offline simulation, the Plant and Controller signals match correctly. However, in external mode, the signal measured by the ADC is significantly different from the original signal sent through Analog Out. The waveform shape is similar, but the amplitude and offset are noticeably different.

The Plant is running on the RT Box, and the Controller is running on a TI C2000 DSP in external mode.

Could this be related to ADC range, Analog Out range, clipping, or some other issue in between the RT Box and DSP signal chain?

Thank you.

[single\_phase\_pv\_inverter\_PI\_c2000.plecs](https://forum.plexim.com/uploads/short-url/l0vah6Ekt85YdKBFAcHdQ6QpCrJ.plecs) (149.4 KB)

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**Author:** ![Oliver\_Schwartz](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/oliver_schwartz/32/6_2.png) [@Oliver\_Schwartz](https://forum.plexim.com/u/Oliver_Schwartz)\
**Post date:** [April 16, 2026, 9:48am UTC](https://forum.plexim.com/t/signal-mismatch-between-rt-box-analog-out-and-dsp-adc-in-external-mode/2998/2 "2026-04-16T09:48:58Z")

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In the target settings for the controller, you have selected an external 3.3 Volt voltage reference for ADC A. Are you sure that you have an external reference voltage connected?

The model works fine if you select the internal 3.3 Volt reference.

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<div class="post-metadata">

**Author:** ![Seoyoung](https://avatars.discourse-cdn.com/v4/letter/s/ecae2f/32.png) [@Seoyoung](https://forum.plexim.com/u/Seoyoung)\
**Post date:** [April 20, 2026, 4:45am UTC](https://forum.plexim.com/t/signal-mismatch-between-rt-box-analog-out-and-dsp-adc-in-external-mode/2998/3 "2026-04-20T04:45:04Z")

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Thank you for your suggestion.

You were right. ADC A was configured to use an external 3.3 V reference, but I did not have an actual external reference voltage connected.

After changing the ADC reference setting to the internal 3.3 V reference, the measured signals became consistent and the system is now working correctly in external mode.

Thank you very much for your help.