ESP-32 supply voltage: 3.3V Voltage drop across LED = 1.8V Desired current flows through LED = 10mA
Resistance R = (3.3-1.8)/(10*10^-3) = 150
Connect led and resistance in series to ground
Code
/*Paste your code here*/
// source current configuration
#define led_pin 4
void setup() {
// put your setup code here, to run once:
pinMode(led_pin, OUTPUT);
}
void loop() {
// put your main code here, to run repeatedly:
digitalWrite(led_pin, HIGH);
delay(400);
digitalWrite(led_pin, LOW);
delay(800);
}