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akidder

1519 Posts
Posted - 13 Mar 2002 :  19:24:11  Show Profile  Email Poster
Q: I'm not sure my PC serial port is working. How can I test it?

The most reliable way to test your serial port is to view the ouput on an oscilloscope. The TX and RX signals are on pins 2 and 3 of DB9 connectors (TX is on pin 3 of DB9M and pin 2 of DB9F sockets).

If you don't have an oscilloscope, try the paper clip loopback test:
  1. Bend a paper clip open so that the ends are pointing in the same direction.

  2. Stick the ends of the paper clip into sockets 2 and 3 of the DB9F socket of your serial port cable.

  3. Run a terminal program on your PC and open the serial port you are testing.

  4. Type some characters.
    You should see the characters appear on the screen (they will appear double if you have local echo enabled)

  5. Remove the paperclip from the DB9 socket.

  6. Type characters again.
    This time you should see no characters echoed to the screen (if you're using local echo, you should see one character instead of two).


Further Reading

  • Troubleshooting debug port connections


    • -----------------------
    Drew Kidder
    ADS Technology Transfer

    Edited by akidder 19-Jul-2006: Add link to troubleshooting topic.
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