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Say you use PuTTY serial mode and a USB to RS232 cable. Can you send messages to yourself if you wire the TX of the cable back to its RX, not haphazardly, there's probably a bit more set up detail. I'm just wondering if it's possible to self-talk on the putty terminal using serial by routing wires back to yourself.

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    \$\begingroup\$ yes , you can. just short rx to tx. .... that is called local loopback \$\endgroup\$ – jsotola May 3 '18 at 21:43
  • \$\begingroup\$ @jsotola would that essentially look like an echo or you just typing on the terminal? \$\endgroup\$ – ポール May 3 '18 at 21:44
  • \$\begingroup\$ It would look like you are typing on the terminal, from my experience doing it in Minicom (another serial program). You may need to turn off hardware control. \$\endgroup\$ – Jim May 3 '18 at 21:46
  • \$\begingroup\$ normally, you do not have local echo mode turned on. .... so when you type, you see the typed characters because the remote device (or a loopback like yours) is sending the keystrokes back to you ....... if you have the local echo enabled, then you see characters on the screen even if there is no communication, and you see a doubling of characters if the remote device is also echoing characters \$\endgroup\$ – jsotola May 3 '18 at 21:50
  • \$\begingroup\$ Tying the handshaking line CTS on, or to RTS may be needed if youn have handshaking. Realterm lets you see the state of the handshake inputs (CTS), and set the output (RTS), and send <break> on TXD line, this can help debugging and wiring it up. \$\endgroup\$ – Henry Crun May 3 '18 at 22:48
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Yes that usually works. And you don't have to provide anything special. If you are paranoid you can place a series resistor there when doing the connection, but that is not necessary as the voltage levels on the pins are compatible.

It will look like a loopback, depending on the terminal settings you might see everything twice if the program is printing the typed stuff on its own already.

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Yes, it will work. It is a very convenient test when solving communication issues with devices to pinpoint where the problem is.

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