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Cannot de-initialize USB Host pull down on STM32F407

Question asked by olov.rosen@hotswap.eu on May 17, 2017
Latest reply on Oct 6, 2017 by waclawek.jan

For our application we use a USB Host to communicate with a HID class device. We've constructed a way to measure the state of the device by measuring the Impedance on the USB datalines. This requires that the datalines are in a high impedance state. 

 

Our problem is that we cannot put the USB datalines in a high impedance state after the USB Host has been initialized.

It seems that, once the USB has been power the pull-downs can only be disabled trough a reset.

 

The USB de-iniitialization function does not affect the GPIO.  It seems they cannot be re-configured to something else.

Is there a way to properly disable the USB and return the original GPIO functionality to these pins?

 

We use STM32CubeMx Together with Atollic truestudio.

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