How many UNO pins have internal pull up resistors?

Question

As the title implies. thank you in advance.

Note that you need to initialize the pins as INPUT_PULLUP to actually enable the pullup resistor. (Just in case this isn't clear.) — orithena, Jan 9 '20 at 11:25

Majenko · Accepted Answer · 2020-01-07 15:47:55Z

3

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

answered Jan 7 '20 at 15:47

Majenko♦

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Thank you very much :) This is NOT the case in other Microcontrollers am I right?
– Abdalrahman Seliem
Jan 7 '20 at 15:50
2

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.
– Majenko ♦
Jan 7 '20 at 15:52
1

Also some MCUs (such as STM32) have also pull down resistors.
– Michel Keijzers
Jan 7 '20 at 16:18
2

@MichelKeijzers So do modern PIC32 chips (anything since the release of the MX1 / MX2 series).
– Majenko ♦
Jan 7 '20 at 16:23
1

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
– Duncan C
Jan 7 '20 at 21:34

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