HSE Bypass mode - Possible use of OSC_OUT as GPIO

BPart.1 · ‎2025-10-24

Hi I am looking into using STM32F446RCTx for my design, which includes 2 x USB FS 2.0 (1 x Host + 1 x Device). Hence need to provide an external HSE. I want to use an Oscillator, meaning I setup the HSE as "Bypass Clock Source" .

With this setup I planned to use the pin 6 (PH1_OSC_OUT) as a GPIO for other functionalities. But the STM32CubeMX setting does not let me do this.

I see that this pin will be (OSC_OUT) High Impedance as per RM0390 - Page 120. Am I right in say that I MUST leave this pin NC and cannot free up to use as GPIO?

Thanks.

mƎALLEm · ‎2025-10-24

Hello,

I think that possibility is available only in newer products. STM32H7 can do that.

According to the STM32F446 reference manual. It says not. But I can check internally. Internal ticket number 220390 not accessible by the community members.

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BPart.1 · ‎2025-10-24

Hi Thanks for checking this out.

BPart.1 · ‎2025-10-30

Hi, the answer to the original question what I should do with the OSC_OUT pin is fine for me to get on with the design for now. I am however is still waiting for the answer FROM ST on if there is a way of using this port as GPIO. Your associate mƎALLEm mentioned that he will find this out from ST.

Thanks

mƎALLEm · ‎2025-10-30

Hello @BPart.1 ,

I'm still waiting a confirmation from the internal team. If I have any feedback I will get back to you.

Thank you for you patience.

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