STRAY PIN CAPACITANCE EFFECTS ON SIGNAL READING COUPLED BY OPTOCOUPLER ON MICROCONTROLLER BOARDS

Reading high frequency signal could have possibility effecter by the internalcapacitance from microcontroller pins. Study case is between Arduino and encoder couplerwith optocouplers. High frequency signal is struggle to high logic due to slower rise time.Turns out slower risetime caused by internal capacitance causing 1st order response system,by adding pull-up resistor on input pin, risetime could be reduce. As final result, addingpull-up resistor does affecting the rise time, but the there are still other factors besideinternal capacitance.