How can I perform an RS232 loopback test to confirm the serial port on a UDS/Cobox is working correctly?

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Here is the procedure to perform a serial loopback test on a Lantronix Device Server running CoBos, i.e. a UDS, SDS, WiBox or xDirect.

1. Open Setup Mode. See the chapter on "Configuration via Telnet or Serial Port (Setup Mode)" in the User Guide for your device server, available from:
   http://www.lantronix.com/support/downloads/
   
2. Assign an IP address to the UDS or other CoBos sevice server and configure the serial port to listen on TCP port 10001. See the example session at the end of this article for the procedure.
   
3. Enable telnet on the UDS's serial listener, also shown in the example session below.
   
4. Use a paperclip or other stiff conductor bent into a U shape to connect pins 2 & 3 on the device server's serial port.
   1. Pin 1 is at the upper right end of the top row on the serial port connector on the UDS1100 and xDirect.
   2. Use a DB9 F-F Gender changer on the Serial 1 port of a two-port UDS, SDS or WiBox to make it easier to jumper pins 2 and 3.
      
5. From a PC or other host, ping the IP address you assigned to the unit you are testing.
   
6. If you are successful in pinging the device, telnet into the IP of the device server and port 10001. Example:
   telnet 192.168.11.178 10001
   
7. Type something into the telnet window. If you type "good morning", you should see "good morning" in the telnet window.
   
8. If the data you type into the telnet session is echoed in the telnet window your test was sucessful.
   
9. Remove the loopback jumper and type some more text into the telnet window. You should not see anything echoed back.

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Example configuration session:

MAC address 00204A9B007D
Software version V6.6.0.1 (080808)

Press Enter for Setup Mode

<summary and menu deleted for brevity>
9 Save and exit Your choice ? 0

IP Address : (000) 172.(000) 18.(000) 11.(000) 190
Set Gateway IP Address (N) ? Y
Gateway IP addr (000) 172.(000) 18.(000) 0.(000) 1
Netmask: Number of Bits for Host Part (0=default) (0) 0
Set DNS Server IP addr (N) ? N
Change telnet config password (N) ? N

<menu deleted for brevity>
9 Save and exit Your choice ? 1

<options deleted for brevity>
DisConnMode (00) ? 40 (Telnet Com Port Cntrl Enabled)
<options deleted for brevity>

<menu deleted for brevity>
9 Save and exit Your choice ? 9

Parameters stored ...

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When you are finished with the loopback test, in most cases you should disable telnet:

<summary and menu deleted for brevity>
9 Save and exit Your choice ? 1

<options deleted for brevity>
DisConnMode (40) ? 00
<options deleted for brevity>

<menu deleted for brevity>
9 Save and exit Your choice ? 9

Parameters stored ...

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[Originally Published On: 03/27/2003 10:55 AM]