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I have an Arduino Due and I want to connect the output from the DAC as an input to an Arduino Uno's analog input pin. From this link http://forum.arduino.cc/index.php?topic=164763.0, user DuaneB suggested that a resistor should be used in series with the DAC output to prevent an excessive flow of current that could damage the pin. But he was talking about this when the question was about powering a motor using the current generated from the DAC's voltage.

However, is this series resistor required when simply connecting the output of the pin to the input of another pin? I haven't seen any issue when connecting the output of my Raspberry Pi's GPIO to an arduino's input.

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The inputs to Arduino pins are CMOS inputs, and present very high impedance. (There is a tiny capacitor on every CMOS input, and the only current into the input is the very small amount needed to charge that capacitor.)

You don't need resistors when connecting inputs and outputs (digital or analog) between Arduinos. Should be the same with Raspberry Pi GPIO lines, or any other CMOS devices.

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  • Do you mean the gate-channel capacitor in the MOSFETs or something totally different?
    – Paddy
    Mar 10, 2019 at 2:30
  • I’m not an electrical engineer, and don’t remember the specifics. Google CMOS and read up on it. CMOS inputs present very high impedance to DC, and only require a tiny flow of current to switch states.
    – Duncan C
    Mar 10, 2019 at 14:03

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