DEC740 Reset or Serial Install

[Azulath]

I have purchased a DEC740 but unfortunately, I have messed up my network settings due to an error and now I do not know how I can connect to this device.

I have looked for a reset button, but I haven't found anything like that and my notebook just gets a self assigned IP with no way to connect to the router. (The IP it pick is 169.254.165.210 with a 0xffff0000 netmask. I have tried pinging the broadcast address, but I do not get any response.)

I now wanted to use a serial USB install and connect the device like so, but I also cannot see any device like ttyS0 or ttyUSB0.

Any help would be appreciated!

Edit 1: After I reconnected the device via USB I did find a couple of /dev/ttySX devices and /dev/ttyS0 sort of opens a connection with "sudo screen /dev/ttyS0 115200". Unfortunately, nothing happens afterwards and the screen simply remains empty.

Edit 2: ok ttyS0 is something different. I'm also using the cable the came with the device, so I assume when I connect this is should in fact by ttyUSB and not ttyX.

Edit 3: I sort of fear that the serial port has been deactivated after the "successful" configuration...

[meyergru]

You should first try to find the correct USB device. If you use a Linux machine to connect, try lsusb. There should be a device like this:

Bus 002 Device 002: ID 04e2:1411 Exar Corp. XR21B1411

Next, try to locate the ttyUSB0 or ttyXRB0 line to connect to. I usually use cu -l /dev/ttyUSB0 -s 115200, but it should work with screen as well.

If you get not output, it may be that the serial line is not active under the booted OS, however, when you reset the DEC7x0, you can interrupt the boot process. Matter-of-fact, there is a standard BIOS that can be configured via the serial interface.

Using that, you can boot from an USB stick via UEFI and reconfigure the whole thing.

[Azulath]

Thank you very much for the response. I have already discovered the device via lsusb, unfortunately there is no /dev/ttyUSB0 nor /dev/ttyXRB0.

That being said, I would like to point out that this is the first time I try to use the serial interface of a device and therefore I could make some noob mistake in the process.

As a system, I'm running 6.1.22-1-MANJARO if this is any help.

[meyergru]

You probably need to load some driver module like xr_serial. It may be contained in an add-on package with extra kernel modules. Under Ubuntu 22.04, the driver is present.

[Azulath]

A quick google search did not reveal the need to install or load drivers on Manjaro, but I will continue to search more thoroughly.

Maybe a reboot is required? Not sure though since I did not install anything.

As for the DEC740 device, I have plugged in the cable that came with the firewall into the microUSB port labeled with "serial" and I am using a random USB-A port on my notebook. I assume this checks out?

[cookiemonster]

I don't use manjaro but on an ubuntu system all I need to do is plug the usb-to-serial cable, find the USBtty in dmesg and then launch minicom with it i.e. "sudo minicom /dev/tty0USB0" . Then within minicom set the baud rate, etc. Just two values.
Just look in dmesg for now.

[Azulath]

After a reboot of the notebook and attaching the DEC740 to a different USB port I am able to see /dev/ttyUSB0

However, I am not able to enter much. It does seem to connect to it though, since once it mentioned something like amd/freeBSD and another time it asked for a login but I was not able to enter anything. If I press ctrl-a for a while it prints ^A, but ctrl-a-z does not show any help regarding special keys.

As terminal software, I'm using the normal GNOME one and I have also tried macOS' terminal when connecting via ssh.

I am also able to open both minicom and screen at the same time, whereas an additional minicom says the device is locked.

I rebooted the device again and this time I was able to access the firewall. So, now I can configure it properly again and set it up. Thank you very much for your help  :)