PA1 Voltage Level in Reset State – Nucleo-F446ZE

usinfi · ‎2026-04-16

Hello,

While using the Nucleo-F446ZE, I observed that pin PA1 remains at approximately 2.6 V during reset, even when an external pull-down resistor is applied. On this development board, PA1 can be configured as the RMII Reference Clock. However, I have removed SB13, so this function should be disconnected and no longer influence the pin. Given that no internal or external circuitry should be driving this pin and considering that an external pull-down resistor is present I would expect PA1 to be held at 0 V during reset.

Why the pin is not pulled low in this condition?

Andrew Neil · ‎2026-04-16

Have you checked the schematics to be sure that there isn't anything still connected - even after removing SB13 ?

What pull-down value are you using? Are you sure it is well-connected?

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mƎALLEm · ‎2026-04-16

Hello @usinfi and welcome to the ST community,

Nothing special on PA1:

Check again SB13 is well removed/unsoldered and you haven't nothing connected externally to it.

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TDK · ‎2026-04-16

Where exactly are you measuring it? It's not exposed on a header.

If you are measuring on CN9 pin 13, you will need to close SB11 which is open by default.

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mƎALLEm · ‎2026-04-16

Not exposed on the Zio connector

But exposed on CN11 (Morpho connector not mounted by default on the board):

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