So guys ... if got an DFRobot Mega with ATMega1280. This is the code: void setup(){ pinMode(39, OUTPUT); } void loop(){ digitalWrite(39, HIGH); Serial.println(digitalRead(39)); delay(100); digitalWrite(39, LOW); Serial.println(digitalRead(39)); delay(100); } To pin 39 is an Opto…

digitalRead always LOW / 0

SurferTim April 15, 2012, 12:51pm 2

Do you have a current limiting resistor in series with the opto-isolator input?

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