[Solved] Preventing Crosstalk on ESP32 DevKit V1 Analog Pins (GPIO 34, 35, 36, 39)

Good morning,

I'm using the ESP32 DevKit V1 board, when reading the input voltage from the analogue pins (GPI: 34,35,36,39), there is some crosstalk and even though the wire is "hanging in the air" or plugged into the prototyping board, out of nowhere, the voltage appears long enough that 'digitalRead()' perceives it as high, and holds above 100ms, I know this because I added an additional instruction to check the status after 100ms. The problem occurs despite a 1 kOhm resistor being soldered in. I don't know how to solve this. Anyone know perhaps how to fix it?

I would also add that pinMode set to INPUT because INPUT_PULLUP gave even worse results and the voltage appeared more often. Previously (without the resistor) all I had to do was hold a wire connected to the input in one hand and a 3.3V wire in the other hand and the voltage was already high enough. for the program to read it as a high state.

I would be forgetting... my observations showed that when, for example, I have a meter plugged into the circuit for 5 minutes (minus of the meter to any GND, and plus anywhere in the circuit - e.g. at the resistor leg), crosstalk does not appear at all. On the other hand, if I briefly unplug the meter, they already occur. Could this suggest that the resistance of the meter "kills" the crosstalk and it is enough to plug in a larger resistor?


Thank you very much for taking the time to read and I hope for a quick reply .

Askabius wrote:

The problem occurs despite the soldering of a 1 kOhm resistor.

Where did you connect this resistor ?

TvWidget wrote:

Askabius wrote:

The problem occurs even though you soldered a 1 kOhm resistor.

Where did you connect this resistor ?

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Added after 3 [minutes]:

I also came across information that there should be something like this:
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However, I'm not sure I got it right :/.

The latter is the correct way.
If the wires are not very long then you can dispense with the resistor. In this case, you should configure the input as PULL_DOWN.

Askabius wrote:

when reading the input voltage from the analogue pins (GPI: 34,35,36,39)

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These GPIOs do not have internal pull-up or pull-down resistors built in, so they can only operate only in INPUT mode. If you want to connect buttons to these inputs, then they must be pre-polarised by using external pull-up resistors to 3V3 or pull-down resistors to ground.
https://randomnerdtutorials.com/esp32-pinout-reference-gpios/

Askabius wrote:

Anybody knows maybe how to fix it?

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Use one of the circuits below (R = 10k)



Elimination of switch contact vibration remains an open question:
http://mikrokontrolery.blogspot.com/2011/04/przycisk-drgania-stykow-debouncing.html

Thank you very much for your help, I will do everything according to the diagram. I understand that MCU stands for ground, yes?

EDIT: I checked that MCU stands for microcontroller. In that case, the ground is "at the bottom of the schematic", in the sense in which VCC is at the top of the schematic?

Askabius wrote:

I understand that MCU means ground, yes?

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MCU stands for the input to the processor. Ground is indicated as an inverted triangle.

khoam wrote:

Askabius wrote:

I understand that MCU means ground, yes?

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MCU stands for the input to the processor. Ground is indicated as an inverted triangle.

Ok, thank you. I consider the topic closed

khoam wrote:

Askabius wrote:

I understand that MCU means ground, yes?

.
MCU stands for the input to the processor. Ground is indicated as an inverted triangle.

Ok, thank you. I consider the topic closed

Added after 1 [minute]:

The answer is a diagram sent by the user.