Monitoring Vin pin

Is there a way to monitor the Vin pin in order to get its voltage thru some internal function?

After 1600 posts you should know to at least post WHICH board you use and how to pick the right (forum) board....

On most boards, possible, jut add a voltage divider.

I'm using an Uno and nano but let's just say for arguments sake it's the nano. What I want is to get the voltage into the Vin pin from code such that if I connect an lcd to the nano I can get the Vin instantaneous voltage displayed on the lcd much like a phone displays it's charge.

But I meant without adding any components. I thought there might be an internal library function that could monitor that.

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I dont know...im asking. If it doesnt exist then it doesnt exist. I just wanted to know if it did because I think it would be useful.

thanks