External Clock Configuration

[Anusree_k]

Hi,

I am using the STM32L031F6 MCU and have configured the internal clock, which is working properly. However, I need to configure the external clock. We observed a pin conflict when changing to the external clock configuration because we are using the PA0 pin for another purpose. In this situation, is it possible to configure the external clock?

Below is the RCC configuration:

Clock configuration

[Andrew Neil]

What does the Datasheet tell you?

[TDK]

Hover over the red region to see the source of the conflict. In this case:

In other words, PA0 cannot be a GPIO if you want to use an external clock. There is no other pin available for this.

[nouirakh]

Hello @Anusree_k 

Can you try to use HSE bypass mode, in this mode you can provide an external clock signal directly to the HSE input pin (PA0). This mode only requires PA0, and PA1 can be used for other purposes.

Steps to Configure HSE in Bypass Mode:

1. Connect External Clock Signal to PA0: Ensure that your external clock signal is connected to the pin.
2. Configure HSE in Bypass Mode: Update your RCC configuration to enable HSE in bypass mode.

Using the HSE in bypass mode is the best solution if you need to use an external clock and PA0 is already in use. If this is not possible, consider reassigning the functionality of PA0 or using the internal clock sources.

[SofLit · Accepted solution]

Hello,

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I need to configure the external clock. We observed a pin conflict when changing to the external clock configuration because we are using the PA0 pin for another purpose. In this situation, is it possible to configure the external clock?

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You've already answered the question in your comment: conflicting with another function.

PA0 is already used in your application and in your package you need CK_IN input having the same pin as PA0 (pin 6)

So if you need to use CK_IN you need to replace PA0 by another GPIO pin.

[TDK]

This reply makes no sense for a number of reasons:

• The chip can only run in HSE bypass mode. The user is already "trying" it.
• PA1 is not used.