How do I connect to a terminal to a serial-to-USB device on Ubuntu 10.10 (Maverick Meerkat)?

Question

I am trying to connect minicom to a serial device that is connected via a USB-to-serial adapter. This is a PL2303 and from everything I've read no additional drivers are required. The device is recognised as a PL2303.

I'm a beginner at minicom. Is this the correct command to execute? Or do I need to configure something?

$ sudo minicom --device /dev/ttyUSB0
minicom: cannot open /dev/ttyUSB0: No such file or directory

$ sudo lsusb -v

Bus 002 Device 006: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
Device Descriptor:
  bLength                18
  bDescriptorType         1

$ tail /var/log/syslog  #then removed and attached the device.
Mar 13 23:31:49 ubuntu kernel: [807996.786805] usb 2-1: pl2303 converter now attached to ttyUSB0
Mar 13 23:34:44 ubuntu kernel: [808172.155129] usb 2-1: USB disconnect, address 7
Mar 13 23:34:44 ubuntu kernel: [808172.156321] pl2303 ttyUSB0: pl2303 converter now disconnected from ttyUSB0
Mar 13 23:34:44 ubuntu kernel: [808172.156374] pl2303 2-1:1.0: device disconnected
Mar 13 23:34:52 ubuntu kernel: [808179.497856] usb 2-1: new full speed USB device using uhci_hcd and address 8
Mar 13 23:34:52 ubuntu kernel: [808179.785845] pl2303 2-1:1.0: pl2303 converter detected
Mar 13 23:34:52 ubuntu kernel: [808179.872309] usb 2-1: pl2303 converter now attached to ttyUSB0

Solution 1

First check with dmesg | grep tty if system recognize your adapter. Then try to run minicom with sudo minicom -s, go to "Serial port setup" and change the first line to /dev/ttyUSB0.

Don't forget to save config as default with "Save setup as dfl". It works for me on Ubuntu 11.04 on VirtualBox.

Solution 2

You will need to set the permissions every time you plug the converter in. I use PuTTY to connect. In order to do so, I have created a little Bash script to sort out the permissions and launch PuTTY:

#!/bin/bash
sudo chmod 666 /dev/ttyUSB0

putty

P.S. I would never recommend that permissions are set to 777.

Solution 3

The serial port communication programs moserial or gtkterm provide an easy way to check connectivity and modify /dev/ttyUSB0 (or /dev/ttyUSB1!) settings. Even though there maybe only a single USB to RS232 adapter, the n designation /dev/ttyUSBn can and does change periodically! Both moserial and gtkterm will show what port designation is relevant in their respective pull down menus when selecting an appropriate port to use.

Check out help.ubuntu.com/community/Minicom for details on minicom.

Solution 4

Long time reader, first time helper ;)

I'm going through the same hellish experience here with a Prolific USB <> Serial adapter and so far Linux is the easiest to get it to work.

On CentOS, I didn't need to install any drivers etc.. That said,

• dmesg | grep -i tty or dmesg | grep -i usb showed me /dev/ttyUSB0.
• screen ttyUSB0 9600 didn't do the trick for me like it did in OSX
• minicom is new to me but it was complaining about lack of /dev/modem

However, this helped: https://www.centos.org/forums/viewtopic.php?t=21271

So install minicom (yum install minicom) then enter its settings (minicom -s).

Then select Serial Port Setup and change the Serial Device (Option A) to /dev/ttyUSB0, or whatever your device file is as it slightly differs per distro.

Then change the Bps (Option E) to 9600 and the rest should be default (8N1 Y N)

Save as default, then simply minicom and Bob's your uncle.

HTH.

Solution 5

I had fix this with adduser *username* dialout. I never had this error again, even though previously the only way to get it to work was to reboot the PC or unplug and replug the usb to serial adapter.

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Comments

[Chris Stratton]

Yes, if you run as a regular user permissions could be an issue. Note however that in this question, minicom is being run as root using sudo. 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'

[Don Kirkby]

For more details on the dialout group, see a related question on askubuntu.com.

[abarisone]

Could you please add a little more description about the explanation you provide?

[gatorback]

Cutecom is an intuitive serial-port monitor. Be sure to mind the devices permissions: best to open them up: chmod 777 /dev/ttyUSB0

[Vassilis]

I think that is worth trying to add your user to the dialout and/or uucp group before changing permissions, as you might not need to do that anymore!

[Vassilis]

Also, add user to the dialout group, as you need write access to the device.

[Matthias Dieter Wallnöfer]

Should probably mean /dev/ttyACM0 instead of /dev/ttyUSB0.

[Simon A. Eugster]

@MatthiasDieterWallnöfer it depends.

[ryanjdillon]

Excellent SO writing style :)

[Scott Prive]

I can add an update: @Vassilis answer is true still today (even on Ubuntu 20). If you had ls -l /dev/ttyUSB0 and looked at the device's "group" owner, that would be a clue what group your user needs to be added to. Lastly, the 3rd column is "nobody" permission meaning if you're going to hack permission changes, that's the column you especially do not want to change (it won't help your user, and it may grant permission to insecure processes such as a webserver you run). See: usermod -a -G dialout $USER instead..

[Jesusaur]

I'm able to use screen -U /dev/ttyUSB0 115200 to connect to a PL2303