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I am referring to all digital I/O pins 0 to 13 and A0 to A5.

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    All of them have. Commented Jan 7, 2020 at 15:45
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    Note that you need to initialize the pins as INPUT_PULLUP to actually enable the pullup resistor. (Just in case this isn't clear.) Commented Jan 9, 2020 at 11:25
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    no i dont think it does because it didnt for me Commented Oct 6, 2021 at 21:40

1 Answer 1

Reset to default
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All of them. It's a standard feature on all IO pins in the AVR range.

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  • Thank you very much :) This is NOT the case in other Microcontrollers am I right? Commented Jan 7, 2020 at 15:50
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    Not all microcontrollers have them, that is true (low-end PIC for example). Some only have them on some pins (such as older PIC32MX chips). They are getting more and more popular though (now all modern PIC32MX chips and PIC32MZ chips have them), so more modern chips tend to have them rather than not. Commented Jan 7, 2020 at 15:52
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    Also some MCUs (such as STM32) have also pull down resistors. Commented Jan 7, 2020 at 16:18
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    @MichelKeijzers So do modern PIC32 chips (anything since the release of the MX1 / MX2 series). Commented Jan 7, 2020 at 16:23
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    Note that while all all AVR chips offer pull-up resistors, you have to turn them on. To do that, use the command pinMode(pin, INPUT_PULLUP) to activate the pullup resistor on the pin pin Commented Jan 7, 2020 at 21:34

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