Push button pull up resistor on a 3.3v board.

Other Hardware General Electronics
1

Hi,
I am waiting for my new Genuino 101 board to arrive and I was wondering if using 3.3V would change anything about the recommended 10k pull up resistor when connecting buttons? I read that 3.3v I2C uses 4.7k resistors. I still have a bunch of those but I ran out of 10k's.

2

4.7k would work fine.
But, the internal 10K pull up, pinMode INPUT_PULLUP, will function so why not use it.
.

3

THX!
Is INPUT_PULLUP new? I only knew about setting the button pin HIGH and then waiting for it to go LOW on a button push.

4

New as in three years old, yes.

5

LarryD:
4.7k would work fine.
But, the internal 10K pull up, pinMode INPUT_PULLUP, will function so why not use it.
.

10k internal pullup? I can't find anything online about internal pull-ups on the 101 and
I don't have one to test. Best to use external 4k7 pull-ups I guess. That's a value that
has a good chance of working with any set-up, even long runs.

6

MarkT:
New as in three years old, yes.

Well I get around to make something in Arduino perhaps once a year.^^

Thank you I will use the 4k7's and the 3.3v output, to be safe.

7

MarkT:
I can't find anything online about internal pull-ups on the 101

Just tested it here on my 101 and the following compiles and works just as expected-
ie. Reads HIGH if Pin left unconnected and when you ground the pin it Reads LOW - no external resistor needed.

pinMode(buttonPin, INPUT_PULLUP);