M5StickC built in LED

wikistik

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

Kyklist

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".

wsanders

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

Bear in mind that when you initialize the pin with:

M5.begin();
...
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.

ajb2k3

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

felmue

Hello @wsanders

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

Thanks
Felix

wsanders

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() {
M5.begin();
digitalWrite (M5_LED, HIGH); // turn off the LED
pinMode(M5_LED, OUTPUT);
digitalWrite (M5_LED, HIGH); // off
}
void loop() {
delay(10);
ESP.restart();
}

the LED does not flash repeatedly.