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I am trying to access the Siemens RuggedComm 900W ROS (operating system associated with the Ethernet switch) by establishing a serial port connection.

I have followed the instructions described in the configuration manual - https://cache.industry.siemens.com/dl/files/218/109737218/att_1028764/v1/C79000-G8976-1280_ROS_v4.3_RS900W_ConfigurationManual.pdf starting on page 33 under establishing console connection.

As the instructions say, I open a terminal on my Ubuntu machine and then physically connect the computer to the Ethernet switch using an USB to Serial Port cable (RS232). I then use sudo journalctl --follow and determine that the serial port is identified as ttyUSB0.

I then configure the serial port, resulting in the following parameters:

speed 57600 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl -ixon -ixoff
-iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
echoctl echoke -flusho -extproc

I then run the command export TERM=VT100 to set the terminal id to VT100. I am expecting the login form to appear, but it does not. I have tried unplugging the USB to Serial Port and reconnecting.

2 Answers 2

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I then run the command export TERM=VT100 to set the terminal id to VT100. I am expecting the login form to appear, but it does not.

That's not how this works, at all. Changing TERM does not make the terminal connect to a different line. It does something completely different, and it isn't even read by the terminal at all.

(The $TERM variable actually goes in the opposite direction; it is set by the terminal, and it informs programs such as 'ls' or 'vim' about the protocol used by this terminal model – i.e. what codes change colors, what codes move the cursor, etc.)

To actually connect your terminal to a serial line like /dev/ttyUSB0 – well, most terminals do not have an option to connect directly, so you will need to run a program which does. Common ones are picocom, minicom, dterm, tio, and screen.

For example:

  • picocom -b 57600 /dev/ttyUSB0 (use Ctrla then Ctrlx to exit)

  • minicom -D /dev/ttyUSB0 -b 57600 or minicom -s (use (use Ctrla then x to exit)

  • dterm /dev/ttyUSB0 57600 (use Ctrl] then q to exit)

  • screen /dev/ttyUSB0 57600 (use Ctrla then k to exit)


Once you've connected and logged in, it's the remote system which needs to know your terminal ID. (If it were a Linux or Unix system, that's where you would set TERM.)

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You are doing it wrong.

Its almost like you are trying to configure the serial port to accept incoming connection. While what you have done can configure the serial port it won't provide output or interactivity.

(As per the PDF, although I can see why you might be confused - this is setup harkens back to the bad old days before the existence of the web) you need terminal emulation software. There are no doubt others, but minicom is a common one. This will allow you to configure the serial port and interact with the console.

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