M5StickC built in LED

  • Any insight on how the red led on pin 10 of the M5StickC is wired up?
    I noticed that, using the Arduino IDE
    pinMode(10, OUTPUT);
    turns the LED on and subsequently
    digitalWrite(10, HIGH);
    turns it OFF, while
    digitalWrite(10, LOW);
    turns it ON again

  • Its common to wire a LED to a GPIO (pin) as Active "Low".

    One pin of the LED gets wired to +V and the other pin goes to the GPIO.
    At some point there is most likely a resister to limit the current.

    Apparently its easier (less heat?) for the GPIO (pin) to source power by pulling the circut "low".

  • (I'll go ahead and bump this. So sue me.)

    Bear in mind that when you initialize the pin with:

    pinMode(M5_LED, OUTPUT);
    digitalWrite (M5_LED, HIGH); // turn off the LED

    The LED will blink briefly. I don't know of a workaround. I also know virtually nothing about ESP pin frobbing.

  • It’s a oddity that some pins on the esp32 variant often work backwards

  • Hello @wsanders

    I don't see the brief blink myself, but have you tried to swap the two statements?


  • Thanks! That workaround works.

    You only see the brief flash when applying power or when the IDE uploads the code and hard resets via RTS.

    If you do this:

    #include <M5StickCPlus.h>
    void setup() {
    digitalWrite (M5_LED, HIGH); // turn off the LED
    pinMode(M5_LED, OUTPUT);
    digitalWrite (M5_LED, HIGH); // off
    void loop() {

    the LED does not flash repeatedly.