Hey falks,
I have to questions, but first, I wanna ask one question, and than, the other:
how do you calculate the PULLUP or PULLDOWN resistor for an IC ?
You know, sometimes I use IC's with 3.3V, and sometimes with 5V. So, how do you calculate this ?
I will use those PULLUP or PULLDOWN pins, only for a pushbutton. Therefore, there won't flow to much amps. Only a pushbutton.
Sometimes I use PULLUP, and sometimes PULLDOWN.
For an I2C pull-up you can read this
Thanks, will read this. can I aska you, if there are some questions ??
You can ask the forum whoever knows will answer
If you are looking for a formula, there is none.
The value of the pull-up will depend on your paticular set-up.
Even then, it's more of a good engineering estimate of what would work best.
most processors these days have options to enable internal pull-up/down resistors on their GPIOs which are of course appropriate for their design
Arduino digital pins can be configured as INPUT_PULLUP to enable their internal pull-up resitor (Arduinos don't have pull-down resistors)
Okay, I've read it. And no surprise: I barely understood this 
Is there maybe a way, to try it out ? for example, with a Potentiometer ??
Okay, it is too complicated maybe just give me an example, for an ESP8266-12E Pushbutton with a PULLUP pin.
Use 10K
code that toggles several LEDs, each associated with a button configured with a pullup (see pinMode)
// check multiple buttons and toggle LEDs
enum { Off = HIGH, On = LOW };
byte pinsLed [] = { 10, 11, 12 };
byte pinsBut [] = { A1, A2, A3 };
#define N_BUT sizeof(pinsBut)
byte butState [N_BUT];
// -----------------------------------------------------------------------------
int
chkButtons ()
{
for (unsigned n = 0; n < sizeof(pinsBut); n++) {
byte but = digitalRead (pinsBut [n]);
if (butState [n] != but) {
butState [n] = but;
delay (10); // debounce
if (On == but)
return n;
}
}
return -1;
}
// -----------------------------------------------------------------------------
void
loop ()
{
switch (chkButtons ()) {
case 2:
digitalWrite (pinsLed [2], ! digitalRead (pinsLed [2]));
break;
case 1:
digitalWrite (pinsLed [1], ! digitalRead (pinsLed [1]));
break;
case 0:
digitalWrite (pinsLed [0], ! digitalRead (pinsLed [0]));
break;
}
}
// -----------------------------------------------------------------------------
void
setup ()
{
Serial.begin (9600);
for (unsigned n = 0; n < sizeof(pinsBut); n++) {
pinMode (pinsBut [n], INPUT_PULLUP);
butState [n] = digitalRead (pinsBut [n]);
}
for (unsigned n = 0; n < sizeof(pinsLed); n++) {
digitalWrite (pinsLed [n], Off);
pinMode (pinsLed [n], OUTPUT);
}
}
okay, should I use a higher resistor ? to be sure, that there is no distrubance to gurantee a stable pin-status
by the way: I allways use PULLUP as a button-pin.
thanks mate
Did you read post 5
Then use INPUT_PULLUP in pinMode() and job done
yes I did. But my question has no particular circuit. As I said: I simple PUSHBUTTON... like this sheme here...
Except the ones that do.
Using results from a search, your MCU's GPIO pin max current:
The esp8266 and esp-12e both use the same ESP8266 chip, with the only difference being the number of pins. The maximum current that can be drawn from a single GPIO pin is 12mA.
Wetting current is the minimum amount of DC current necessary to keep a mechanical switch contact on a dry loop in good health. Typically, 1-20 mA in copper wire loops. If a mechanical switch contact is operated with too little current, the contacts tend to accumulate excessive resistance and may fail prematurely.
I would suggest getting the pullup/pulldown current to within 1-5mA range.
Therefore, I would suggest using a 1K to 3.3K pullup/pulldown resistor. This should result in a more robust solution with high noise immunity and high reliability.
That is a particular circuit. You have a single pushbutton on a breadboard and it's only a few inches away from the ESP. So 10K would be fine.
If it's 3 feet away and susceptible to electrical interference I would probably suggest something different. If you use 32 switches again maybe something different.
Do you see my point?
Re post#13 showing 220Ω pulldown resistor. This works out to 14mA current when the button is pressed. I would bump this up to at least 270Ω to get the current calculation within spec.
buttons are typically connected between the pin and ground, the pin configured as INPUT_PULLUP to use the internal pullup resistor which pulls the pin HIGH and when pressed, the button pulls the pin LOW.
Wait a minute, wait a minute. Now I will drop a big`egg right into your nests, falks 
it is rather a bomb, than an egg:
okay, I really thought, that this will be an easy-to-answer question. I was wrong
Yes, it is a single push_button. But it is only one, on each pin (4 pins in total). All other pins are in also in use. For example:
okay, do you again recommending me, to use a 10K resistor for the push_button-pins ?
