Electronic – Should I consider this 1.57V open pull-up pin on ESP32 faulty

esp32inputpullup

I'm working with a ESP32 NodeMCU32 dev board.

When I set INPUT_PULLUP on pin 23, and measure its voltage, I get 1.57V. If I do the same for pin 22, I get 3.23V. Both pins are open (not connected to anything) and I've done these measurements on a "pure" platformio build, code below.

As far as I know, pin 23 used to work as I expected (i.e. like pin 22). Is this board faulty or damaged, or could I be setting something up wrongly?

Could be a red herring, but I'm suspicious that 1.57 * 2 is very close to 3.23.

EDIT: Datasheet (section 5.3) says minimum high DC output is 0.8×VDD, which would be about 2.6V (far higher than the 1.57V I'm getting). I assume this is what the pull up is connected to, so perhaps this indicates the chip is not in spec (faulty).

Here's the code I used for the tests.

#include <Arduino.h>

void setup() {
  Serial.begin(115200);

  pinMode(22, INPUT_PULLUP);
  pinMode(23, INPUT_PULLUP);
}

uint8_t counter;
void loop() {
  Serial.print("Test! ");
  Serial.println(counter++);
  delay(1000);
}

Best Answer

I had in the past a similar problem.

In an NXP LPC2388 powered at 3.3 Volt, a couple of input pins programmed as pull-up pins with nothing externally attached, showed 2.4 Volt instead of 3.3 Volt.

I read carefully the datasheet of the microcontroller and realized that the minimum output voltage of input pins programmed as pull-up was 2.4 Volt.

I suggest you to read the datasheet of the ESP32.

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