04.05.2020»»понедельник

Ubuntu Serial Port Terminal

04.05.2020
Active26 days ago

Is there a way to connect to a serial terminal just as you would do with SSH? There must be a simpler way than tools such as Minicom, like this

I know I can cat the output from /dev/ttyS0 but only one way communication is possible that way, from the port to the console. And echo out to the port is just the same but the other way around, to the port.

How can I realize two way communication with a serial port the simplest possible way on Unix/Linux?

Jun 22, 2014  Traditionally in Linux, the first serial port (COM1) is assigned a name /dev/ttyS0, the second serial port (COM2) assigned /dev/ttyS1, etc. If you specify a serial port name as the first argument of the screen command, the current terminal window where you run screen will be directly connected to the serial port. Configure the Host's terminal emulator for VT102 emulation and the port to 115200 baud, 8 data bits, no parity, 1 stop bit. Use the lowest numbered serial port (e.g. COM1 or ttyS0) from VMware. Step 2: test the login program on the VM (Ubuntu) side. Use the lowest numbered serial port, /dev/ttyS0. Apr 09, 2019  USB-Serial Port adapter (RS-232) in Ubuntu Linux There are two other articles on a serial port adapter for Windows. Below is the instructions for Linux and how to connect your serial adapter while using Linux. This should work for most people using Linux and a serial adapter or usb to rs232 driver which is being discussed. Getting Serial Port to work under Ubuntu! The setup: I have a Intel motherboard inside my office desktop with a built-in serial port. Over the days, I managed to screw up the builtin COM port (and my friends at office did the same to their desktop PCs too. First I installed 'Serial Port Terminal' from Ubuntu Software Center.

  1. Provided by: gtkterm0.99.7+git9d63182-2amd64 NAME gtkterm - A simple GTK+ serial port terminal SYNOPSIS gtkterm options DESCRIPTION gtkterm is a simple GTK+ terminal used to communicate with the serial port.
  2. Generally the preferred solution on access permissions is to assign users who need access to a group which owns the serial port device files and has the needed permission to them - on Ubuntu that is typically 'dialout' – Chris Stratton May 17 '12 at 4:23 2 For more details on the dialout group, see a related question on askubuntu.com.
ihatetoregister
ihatetoregisterihatetoregister
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16 Answers

I find screen the most useful program for serial communication since I use it for other things anyway. It's usually just screen /dev/ttyS0 <speed>, although the default settings may be different for your device. It also allows you to pipe anything into the session by entering command mode and doing exec !! <run some program that generates output>.

Shawn J. GoffShawn J. Goff
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Background

The main reason why you need any program like minicom to communicate over a serial port is that the port needs to be set up prior to initiating a connection. If it weren't set up appropriately, the cat and echo commands would not do for you what you might have expected. Notice that once you run a program like minicom, the port is left with the settings that minicom used. You can query the communication settings using the stty program like this:

If you have done it right; after booting the computer and before running any other program like minicom, the communication settings will be at their default settings. These are probably different than what you will need to make your connection. In this situation, sending the commands cat or echo to the port will either produce garbage or not work at all.

Run stty again after using minicom, and you'll notice the settings are set to what the program was using.

Minimal serial communication

Basically, two things are needed to have two-way communication through a serial port: 1) configuring the serial port, and 2) opening the pseudo-tty read-write.

The most basic program that I know that does this is picocom. You can also use a tool like setserial to set up the port and then interact with it directly from the shell.

rozcietrzewiaczrozcietrzewiacz
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If UUCP is installed on the system, you may use the command cu, e.g.

ktfktf

I found a way using a shell script here that put cat as a background process and a while loop that read the user input and echo it out to the port. I modified it to be more general and it fitted my purpose perfectly.

heemayl
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ihatetoregisterihatetoregister
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Try http://tio.github.io

'tio' is a simple TTY terminal application which features a straightforward commandline interface to easily connect to TTY devices for basic input/output.

Typical use is without options. For example:

Which corresponds to the commonly used options:

It comes with full shell auto completion support for all options.

Thomas
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MartinMartin

This script is based on another answer, but sends everything over the serial port (except Ctrl+Q), not just single commands followed by Enter. This enables you to use Ctrl+C or Ctrl+Z on the remote host, and to use interactive 'GUI' programs like aptitude or alsamixer. It can be quit by pressing Ctrl+Q.

Community
FritzFritz

BTW, the putty package (which does run on Linux) does include serial support.

mdpcmdpc
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Putty works well on Linux and offers some convenience, especially for serial communications. It has one drawback I haven't been able to directly solve: no copy-paste from the Putty window itself. The windows version has a lovely auto-copy to clipboard on highlight, right-click to paste behaviour (and there are excellent plugins for both chrome and firefox to enable the same behavior), but on Linux, no copy love AFAIK.

If the lack of copy is a problem (it is for me) then turn on logging in putty and open a standard terminal window and # tail -f putty.log and bidirectional text is available for standard copypasta action.

gesselgessel

Another issue that can occur is that your user account may need to set to the 'dialout' group to access the serial port.

GAD3R
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dfowler7437dfowler7437

It depends on what you want to do. Do you want to run a shell or applicaiton interactively from the terminal, connect out to another computer over the serial line, automate communication with a device over a serial port?

If you want bidirectional communication then I presume you want something interactive with a human on the terminal. You can configure the system to allow logins from a terminal over a serial port by seting up a getty(1) session on the serial port - getty is the tool for setting up a terminal and allowing logins onto it. Put an entry in your inittab(5) file to run it on the appropriate serial port on a respawn basis.

If you want to connect to a device and initiate automated two way conversations then you could see if expect will get you what you want. Use stty(1) to configure the port to the right parity, baud rate and other relevant settings.

If you want to communicate interactively with another computer over the serial port then you will need terminal emulation software. This does quite a lot - it sets up the port, interprets ANSI or other terminal command sequences (ANSI was far from being the only standard supported by serial terminals). Many terminal emulators also support file transfer protocols such as kermit or zmodem.

The ins and outs of serial communications and terminal I/O are fairly complex; you can read more than you ever wanted to know on the subject in the serial howto.

ConcernedOfTunbridgeWellsConcernedOfTunbridgeWells

As mentioned before you can try picocom. The latest release (2.0) can also be used (safely) to set-up a 'terminal server' since it no longer permits shell command injection. See:

Nick PatavalisNick Patavalis

You might want to take a look at

Pro: doesn't have obvious security problems like minicom or picocom (if you don't have a problem giving the users shell access, no problem, but you most likely do have one if you want to set up a terminal server..)

PeterPeter

You need to be sure to have the correct read write permits on the device, you could see it with:

I rely on the script you found and made some modifications.

For the development systems I've used by now, they used to need:

  • None parity and
  • One stop bit

Those values are the default ones in the script.

So in order to connect, you can use it as simple as follows:

Ubuntu Serial Port Terminal

Example:

Script:

P.S.: You need to know which kind of line feed is using your receiver system since this will determine how you'll need to send the commands in my case I needed a Windows like LF, means that I need to send

ASCII values for:

  • LF : 0Ah, line feed 'n'
  • CR : 0Dh, carrige return 'r'
  • BS : 08h, back space '<-'
Rafael KarosuoRafael Karosuo

As it is not mentioned here already, I'd also mention socat - more info in https://stackoverflow.com/questions/2899180/how-can-i-use-com-and-usb-ports-within-cygwin :

or

(though, I've had the problem of stopping it once it starts running, under MSYS2 on Windows)

sdbbssdbbs

I wonder why nobody mentioned ser2net.

Example /etc/ser2net.conf:

You can connect to serial port as easy as:

Or remotely:

Or even set up port forwarding on your router and expose it to Internet, so that you could connect to it from anywhere (let's skip security issues, I'm talking about flexibility).

Andrejs CainikovsAndrejs Cainikovs

Another easy option is to access the machine over ssh with the -X flag and run a program such as putty or gtkterm.

Hyperterminal

So:

It should launch the graphical interface on your client PC and from there you can access the serial port as if you would be in the host.

Disclaimer: Only tried this with ubuntu machines. I'm guessing that it won't work with machines without graphic interfaces.

From the ssh manual:

-X

Enables X11 forwarding. This can also be specified on a per-host basis in a configuration file. X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring. For this reason, X11 forwarding is subjected to X11 SECURITY extension restrictions by default. Please refer to the ssh -Y option and the ForwardX11Trusted directive in ssh_config(5) for more information.

-Y

Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls.

So use -Y if security is an issue.

GrifoGrifo

Ubuntu Serial Port Terminal Program

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I plugged in a device (i.e. GSM modem) through a serial port (a.k.a. RS-232), and I need to see with which file in /dev/ filesystem this device was tied up, to be able to communicate with it. Unfortunately there is no newly created file in /dev/ nor can be seen anything in dmesg output. So this seems to be a hard question.

Background:

I had never worked with a serial device, so yesterday, when there appeared a need, I tried to Google it but couldn't find anything helpful. I spent a few hours in seek, and I want to share a found answer as it could be helpful for someone.

Hi-Angel

Ubuntu Install Serial Port Terminal

Hi-Angel
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1 Answer

Unfortunately serial ports are non-PlugNPlay, so kernel doesn't know which device was plugged in. After reading a HowTo tutorial I've got the working idea.

The /dev/ directory of unix like OSes contains files named as ttySn(with n being a number). Most of them doesn't correspond to existing devices. To find which ones do, issue a command:

Above is an example output of my PC. You can see the initialization of a few serial ports:

ttyS0, ttyS1, ttyS4, ttyS5.

One of them is going to have a positive voltage upon a device plugged in. So by comparing the content of the file /proc/tty/driver/serial with and without the device plugged in we can easily find the ttyS related to our device. So, now do:

(un)plug a device

Next check the difference between the two files. Below is an output of my PC:

By comparing the three numbers with the dmesg output we can determine which one is the port:

Hence, our device is /dev/ttyS0, mission accomplished!

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Linux Terminal Serial

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