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I have been searching around the Internet to find if there is a way to check whether an Arduino is connected to a PC or not.

For example: if my PC is turned on, the Arduino will listen to any serial commands it receives, BUT if my PC is turned off, the Arduino will receive some random characters.

How can the Arduino check if it is connected to PC and the PC is on?

dda
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TheKayneGame
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2 Answers2

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As suggested by Paul & Gerben, you could check the 5V USB line to see if it has a voltage or not.

I am assuming from your question that the Arduino is not powered from the USB line. I am also assuming that the USB port is not powered when the PC is turned off.

All you have to do is connect VUSB to a digital input through a resistor like so:
Circuit Diagram

Alternatively, you could have the computer send a pre-determined message telling the Arduino that its alive.

If the Arduino receives this message then it lights up the LED on pin 13. If the Arduino hasn't received the "I'm alive" message for a while (ie. a timeout) it then turns off the LED.

A simple PC program could be written to automate this task.

sa_leinad
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jumper reset -> ground and rx -> tx (with power disconnected) connect power, open serial monitor in arduino ide and type anything in and input. if the serial monitor echoes what you typed in, then your connection is good and you should look elsewhere for problems.

Found this solution on the arduino.cc community site.

Almis Peter Salcius
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