2 Aug
2026
2 Aug
'26
9:51 a.m.
That is normal for devices using hardware such as FTDI, CH340 etc. which
have their own specific drivers. However for serial drivers running on a
microcontroller having it's own USB stack such as more modern Arduinos, the
serial device uses a generic USB class called Communications device class
(CDC) and specifically part of the Abstract Control Mode (ACM). This uses a
generic serial driver and gives rise to device nodes called /dev/ttyACMxx.
It's possible that eventually dedicated hardware will appear that also
conforms to this model.
On Sun, Aug 2, 2026 at 4:59 PM Alan Perry via cctalk <cctalk(a)classiccmp.org>
wrote:
I missed the beginning of this discussion but I am
using USB serial ports
(with a variety of USB-serial devices) on Ubuntu everyday in my day job and
the device files are /dev/ttyUSB*. I connect with putty.
alan
On Aug 2, 2026, at 00:27, Torfinn Ingolfsen via
cctalk <
cctalk(a)classiccmp.org> wrote:
To add to what Paul wrote:
Here is a oneliner to check for usb serial ports on a linux machine:
$ ls -l /dev/tty[ACU]*
(the initial '$' is the prompt, don't include it in the command)
run this before and after you plug in your usb serial device, and you
will find it - if it is detected.
If the device only works as user root, you need to create a file to
set ownership, group and permissions on the device when it is plugged
in. This is commonly done through udev / udevadm on linux.
On Sun, Aug 2, 2026 at 4:00 AM Paul Berger via
cctalk
<cctalk(a)classiccmp.org> wrote:
Well the first thing to do is make sure the USB serial device gets
configured, when you plug it in, you should see the serial device listed
in the output from 'lsusb' and there should be messages about it in
'dmesg' (requires root authority). It is possible that the naming
convention for the tty device that get created is different between the
two versions of linux. The usual way is the device gets created
dynamically when you plug in the USB serial device. on my linux,
Devuan which is debian based but unencumbered by systemd, it creates a
device /dev/ttyUSB0 most modern distributions I have seen use names like
this.
Paul.
> On 2026-08-01 21:41, Jon Elson via cctalk wrote:
> Well, everything is a fight!
>
> The project I'm working on is to get a VMS MicroVAX system working at
> VCFMW. The plan was to have serial comm on a Linux laptop connected
> to the MicroVAX. I have the serial comm working on a Dell desktop
> machine, so I just plugged the same USB serial cable into the laptop,
> and NO COMM! I plugged back into the desktop, and serial data works
> fine! I'm totally mystified! The desktop is running an OLD Debian
> kernel (7.11), the laptop is running a late Ubuntu (24.04.4).
>
> I have no idea why the laptop doesn't communicate. I have tried
> minicom, picocom and cutecom, same result on all of them.
>
> Thanks for any help you can suggest.
>
> Jon
>
--
mvh
Torfinn