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The uno has digital pins marked 0-13.

0 is marked as rx and 1 is marked as tx. Can these two pins be used as regular digital pins if i am short of digital pins?

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  • If you are short of digital pins you can aways use the analog pins. They also work as digital pins.
    – Mikael Patel
    May 15, 2018 at 15:44

3 Answers 3

Reset to default
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Yes you can perfectly use these 2 pins as long as your program does not use Serial.

EDIT: Serial data over USB goes through copper traces connected to the rx and tx pins, connecting them to the USB to serial converter chip.

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  • My program is using serial, but pumping it through the usb. Not out of the rxtx pins. Is this still a problem?
    – c_breeez
    Aug 13, 2014 at 20:37
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    It is the same: USB data is passing through RX/TX pins :-(
    – jfpoilpret
    Aug 13, 2014 at 20:39
  • Ok thanks for your great answer and clarifying these points
    – c_breeez
    Aug 13, 2014 at 21:06
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Also you will probably want to ensure these wires are not connected when programming the Arduino. Otherwise you may have problems.

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You can, but it will disable the serial port.

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    No, it's the other way around: the serial port has higher priority. When you enable it with Serial.begin(), you are disabling the normal port operation (pinMode(), digitalRead() and digitalWrite()). With one exception: you can set the RX pin to INPUT_PULLUP, rather than INPUT, which is the default. C.f. the datasheet of the ATmega328P, especially the sections Alternate Port Functions, Data Transmission – The USART Transmitter and Data Reception – The USART Receiver.
    – Edgar Bonet
    May 14, 2018 at 7:57

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