ESP32 Digital Write to input not working

Projects Programming
1

I have hit an issue that I can't tell is something wrong in the compiled behavior or something else I have overlooked, but is really simple in nature.

ESP32 Dev kit type board
I need an input to detect an outside world signal, but for debugging I want to be able to toggle it in code. I set up the pin as an input, then write to the pin which should setup the pull resistors respectively and trigger my code to change behavior. However, the reads for this given pin, indicate the pin never changed state. Respectively, I measure with a DMM and the pin never changes voltages.

Here is code to reproduce the issue

//Ignition signal
const gpio_num_t IGNITION_PIN = GPIO_NUM_19;

void setup() {
  // put your setup code here, to run once:
  //wake up and initialize the serial port
  Serial.begin(115200);
  //wait for the USB serial port to come online if it ever will
  while (!Serial && (millis() < 5000))
    ;  // Wait up to 5 secs for Serial to be ready
  if (!Serial) {
    for (;;) {}  // failed, loop forever
  } else {
    Serial.println("Serial READY");
  }
  pinMode(IGNITION_PIN, INPUT_PULLDOWN);
  digitalWrite(IGNITION_PIN, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
  Serial.println(digitalRead(IGNITION_PIN),DEC);
  delay(100);
}

Monitoring the serial output, I just get "0" forever

here is the device pin definitions

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image1500×1478 167 KB

2

Where did you see that?

3

That may be specific to certain AVR processors, you would need to check the datasheet for the processor in the ESP32 to see how the internal pullup resistors are controlled.

4

Simpler to just wire an input to an output, no? That way, you just remove the code controlling the test output later, leaving your input code unmodified.
That's how I do it, anyway.

Alternatively, a "read inputs" code that stores input states in an array can be followed by a "simulate inputs" code that modifies the array content.
YMMV.

5

If you want to switch the state of the input pin, instead of writing to the pin, call pinMode() again with either INPUT_PULLUP or INPUT_PULLDOWN.

Also see this post https://forum.arduino.cc/t/esp32-pins-that-support-pullup/1173356 it appears GPIO19 does not have the internal pullup. Not sure about this, seems to be some conflicting information.

6

I was hoping there would be an obvious thing, like hey, that pin mux is wrong or etc.

However, I think this will be the easiest approach, rather than spending many hours/days trying to figure out the software solution, I will just tack a wire onto an unused pin and move on as you say.

7

I just tried the pinmode pullup approach as a test, and it doesn't work, so I think you are correct that there isn't a pull-up resistor on this pin. Interesting that I don't see any warnings or etc about this lack of ability. There must not be that level of detail in the board definitions files

8

I have a ESP32 devkitC v4 and INPUT_PULLUP work on it.
However I'm using one of the older cores 2.0.11