M4 Express: Actual resistance value of pull up/down Moderators: adafruit_support_bill, adafruit

[xanatos]

Can't seem to find the actual resistance value of the pull up/pull down settings for digital inputs. ItsyBitsy M4 Express. Need to know actual values to figure into my calculations,

Thanks!

[dastels]

It's not as simple as a resistance to Vcc or Gnd. See section 32.6.3 on page 818 of the SAM D5x data sheet. You can find a copy at https://www.mouser.com/datasheet/2/268/60001507A-1130176.pdf.

If you need to know/control exactly what the pull up/down is, don't enable the internal pull up/down and use an external resistor.

Dave

[xanatos]

Thanks Dave. Page 818 is all about "OSC32KCTRL – 32KHz Oscillators Controller" - but I'm guessing it'll be in here somewhere :) I just need to be sure the pullups are in excess of 100k effectively. If not, like you said, I'll need to use external pull-ups/downs.

Thanks!

Dave

[dastels]

I must have a slightly different version locally. Section 32 starting on pg 883.

Dave

[xanatos]

Thanks Dave, I did find the section... trying to make sense of it now :)

Dave

[westfw]

Actual values are down in the "Electrical Characteristics" pages (54.9 in my copy):
"Somewhere between 20k and 60k" is probably not what you were hoping for!

Screen Shot 2022-07-04 at 7.23.26 PM.png (79.4 KiB) Viewed 49 times

[xanatos]

LOL! Thanks for that. Yes - I'll definitely be using external pullups on the lines that I'm concerned with! :)

Dave