7i73 inputs question (pull-down resistors) (SOLVED)

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17 Mar 2021 21:24 - 17 Mar 2021 21:46 #202647 by spumco
Wiring up my first Linux/Mesa machine now and am in need of some guidance on 7i73 inputs.

Manual states P1/0 to P1/7 P2/0-P2/7 require pull-up or pull-down resistors when used for switch sensing.

So... if one side of a momentary switch is connected to the 3.3v supply on 7i73 (P/29), and the other is connected to P1/7 P2/7, then I would also connect a 4.7k resistor between P1/7 P2/7 and GND - making it a pull-down resistor?

If I have four switches on P1/4 P2/4 through P1/7 P2/7, each one would need a 4.7k resistor connected to GND (along with the switch conductor)?

If I've got it right, any confirmation would be helpful. And if I'm wrong, an explanation in really small words and a diagram would be favorite.

Thanks,
Ralph

Edited to correct port designation error
Last edit: 17 Mar 2021 21:46 by spumco.

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17 Mar 2021 21:30 #202649 by PCW
That's correct.

The pins have no internal pull-up or pull-down resistors
so have an undefined state if left unconnected (when the switch is off)

The pull-up or pull-down resistors define the pin state when unconnected
The following user(s) said Thank You: spumco

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17 Mar 2021 21:45 #202651 by spumco
Thanks much, looking forward to getting this thing moving around.

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