HOW TO: Determine if Digi Acceleport Serial Card ports are working in Windows 95/98/ME


If you have a modem or loopback plug, you can verify that the Digi ports are functioning by downloading TTY.exe to test the ports.  Try using one of the following methods to troubleshoot and verify functionality of your Serial port(s).

Modem method:

  1. Connect your RS232 analog modem to the Digi serial port you wish to test, using a serial cable pinned correctly for Modem operation with your Digi serial port (typically a straight-through or "modem" cable).
    Cabling information for a number of common Digi pinout combinations can be found here if needed.
  2. Run the tty.exe executable and choose Settings.
  3. Select the com port to which you have your modem physically connected.
  4. Configure the communications settings to match the modem and choose OK.
  5. Choose Action, then Connect

You should be at a modem command prompt (you will see a blinking cursor). Try typing AT and hit return. The modem should respond with an OK. This will show that the data was sent to the modem and a response was received back from the modem.  If you type AT but don't see it echo back, or you see it echo but you don't get an OK response, try typing "AT&F" and hit enter instead.  This will return the modem to factory defaults, and will hopefully allow you to see the command you type as well as it's response.

Loopback Plug method

If you do not have a dialup modem to test with, but have a loopback plug instead:
  1. Insert the Digi loopback plug in the serial port you wish to test.  If you don't have a Loopback plug and would like to know how to make one yourself, see the following article:
    How to make an RS-232 loopback plug
  2. Run the tty.exe executable.
  3. At the tty.exe session prompt, try typing on the keyboard. The characters that you type within the terminal session should be echoed back to the console. If you can see what you are typing, this shows that data is being both transmitted and received on the port.

Back-to-Back method of testing two serial ports simultaneously:

When using Digi serial ports, it is possible to start two sessions of TTY.exe (each one pointing to a different Digi serial port), and test two ports simultaneously as long as you have a properly pinned cable (use a null modem pinout) to allow for back-to-back operation.

Cabling information for a number of common Digi pinout combinations can be found here if needed.
  1. Set the TTY.exe session parameters within each session so they match, i.e.use the same baud rate, parity, and stop bits in each session.  This should prevent seeing garbage on the other screen during your test due to baud or parity mismatch.
  2. Type some characters in your active tty.exe session window.
  3. Check the other tty.exe session to see if the characters you typed in step 2 are visible.
  4. Make the other tty.exe session active, and type some different characters from step 2.
  5. Check the other tty.exe session to see if the characters you typed in step 4 are visible.

If you see the characters you typed appearing in the opposite window, then the ports are communicating.  If the characters appear in neither window, or one window but not the other, you'll want to recheck your cable wiring.

If you verify the cable is wired properly and works outside of the current environment you're testing, you may want to contact Digi Technical Support for additional guidance, or to pursue an RMA/Repair.
Last updated: May 20, 2019

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