# Arduino Based Auxiliar MCU

**URL:** <https://klipper.discourse.group/t/arduino-based-auxiliar-mcu/17724>\
**Category:** Developers\
**Created:** [July 17, 2024, 2:28pm UTC](https://klipper.discourse.group/t/arduino-based-auxiliar-mcu/17724 "2024-07-17T14:28:36Z")\
**Posts on this page:** 1\
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**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\
**Post date:** [July 17, 2024, 4:17pm UTC](https://klipper.discourse.group/t/arduino-based-auxiliar-mcu/17724/4 "2024-07-17T16:17:37Z")

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> [@guilherme.parreira](#):
>
> Since I got good results (equivalent to PA, with automatic gain calibration) by reading just step and dir pins, I think it can be even better by having acces to the step commands prior to execution.

Well, this is exactly what Klipper is about:

- The MCU only receive processed commands and executes them. The processing is done on the host
- If you want to access the “raw” steps before being send to the MCU then you need to do this via a host module

Imagine, one would send your controller steps that already “contain” Pressure Advance modifications because the host calculated them in and then your MCU code puts another similar modification on top. This probably would lead to pretty much unpredictable results.

As it stands: Klipper host calculates and Klipper MCU executes. Working around this basic philosophy probably is a bad idea.

But then again, I’m not a core developer, so I happily stand corrected.

EDIT:  
To add: you might also greatly profit from the tools that Klipper is providing, e.g. the so called [MOTAN](https://www.klipper3d.org/Debugging.html#motion-analysis-and-data-logging) tools that allow in-depth analysis of the motion commands that Klipper host has calculated.  
This might come in very handy during your development and to see, what is going on. See for an example [Regression in dynamic PA - #7 by dmbutyugin](https://klipper.discourse.group/t/regression-in-dynamic-pa/17260/7)

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