# Ringing at GPIO and MOSFET
**URL:** https://community.simplefoc.com/t/ringing-at-gpio-and-mosfet/384
**Category:** hardware support
**Created:** [December 28, 2020, 5:34pm UTC](https://community.simplefoc.com/t/ringing-at-gpio-and-mosfet/384 "2020-12-28T17:34:26Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Juxo](https://community.simplefoc.com/u/Juxo)
#### Post date: [December 28, 2020, 5:34pm UTC](https://community.simplefoc.com/t/ringing-at-gpio-and-mosfet/384/1 "2020-12-28T17:34:26Z")
I hope there is a real professional in electronics in the community.
The picture below shows the signal of PWM output of STM32 in red and the signal after MOSFET of a DRV8302 driver board.
Massive ringing on both lines. This is captured at 6V rising. At my usual 20V I see -16V peak-output of the driver on each phase.
I can’t believe that this wave-form-fit is random.
I’m aware that the Drain-to-Source-voltage of a half-bridge tends to ring. Usually the inductivity of the motor is smoothing the current.
Because I’m working with a motor typ that has nearly no inductivity I was faced with the problem that I loose 50% of efficiency with this ringing. If I add a 3A toroidal inductor to each phase the current consumption for an equal load drop by 50%. But this double the size and weight of the ESC, adding additional resistance and limits the current to the max of the inductor.
The question is: is it possible to influence the ringing of the half-bridge by flattening the PWM Input. How to do? Or is it just the feedback of the MOSFET that I can see on the GPIO output.
Additional question: Is there another way to smooth the current of a driver even if I have no inductive load.
Thanks in advance for any hint.
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### Author:  [@runger](https://community.simplefoc.com/u/runger)
#### Post date: [February 24, 2021, 12:38pm UTC](https://community.simplefoc.com/t/ringing-at-gpio-and-mosfet/384/2 "2021-02-24T12:38:27Z")
Too bad no responses on this, I would have liked to learn the answer. Did you find a solution?
I wonder where the problem lies? Is it a grounding thing, since both are ringing - maybe solved with more capacitance to support the transitions?
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### Author:  [@Juxo](https://community.simplefoc.com/u/Juxo)
#### Post date: [February 25, 2021, 6:44am UTC](https://community.simplefoc.com/t/ringing-at-gpio-and-mosfet/384/3 "2021-02-25T06:44:36Z")
Hi @runger,
With a lot of inductance the effect disappears after the coils. Never tried to use capacities. The driverboard died short after the first test. I switched to an Infineon board and had no such ringing.
But within the next days I will setup a new combination of bluepill and 8302. Then I will evaluate this again.