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Unknown characters in serial I/O when telnet session is opened

0 votes
I have an intention make a simple serial to TCP converter which reads values from a serial port connected A/D converter. I have succesfully followed the new project wizard to implement serial to TCP/Serial transfer service on my Connect ME with Net+OS 7.5.

What I want to undestand is that when a telnet session to device is opened, I receive on the serial RS232 side characters looking like this: ÿû ÿûÿû'ÿýÿûÿý . The RS232 interface of the dev board is connected to a PC.

Are these characters an intention to be send every time a new session is opened?
If yes, is it something receiver connected to RS232 should handle?
Can these be suppressed?
asked May 26, 2021 in NET+OS by phy123 New to the Community (6 points)

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2 Answers

+1 vote
Are you using the sample application TCP Serial Bridge? I do not recall seeing those characters? IS it possible that the telnet software you are using is sending some terminal setup information? Can you try using a raw connection instead of telnet or try using a different telnet client.
answered May 26, 2021 by LeonidM Veteran of the Digi Community (4,490 points)
0 votes
Thanks for fast reply again LeonidM.

Yes, I mean the sample application project which is called in the new project wizard TCP/Serial transfer service, I guess we are talking about the same.

I'm familiar with PuTTY so I've been using that as telnet client. I compared to old TeraTerm installation in Vista machine and opening the telnet session with that didn't result those characteristics.

So, I looked more closely to PuTTY telnet session settings and found out there is selection for telnet negotiation mode. Selecting passive instead of active (default), opening telnet session in passive negotiation mode doesn't send those characters in to serial interface.

Also, opening the session in raw connection type in PuTTY, doesn't send characters to serial interface.

So we can conclude its client and its settings dependent.
answered May 27, 2021 by phy123 New to the Community (6 points)