Intel Motherboards - Serial Ports (COM1/COM2) not working on J3455M

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Serial Ports (COM1/COM2) not working on J3455M

Printed From: ASRock.com
Category: Technical Support
Forum Name: Intel Motherboards
Forum Description: Question about ASRock Intel Motherboards
URL: https://forum.asrock.com/forum_posts.asp?TID=4181
Printed Date: 22 Jul 2025 at 9:18am
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com

Topic: Serial Ports (COM1/COM2) not working on J3455M

Posted By: Natanji
Subject: Serial Ports (COM1/COM2) not working on J3455M
Date Posted: 06 Jan 2017 at 7:18am

" rel="nofollow - Since I am trying to run my J3455M as a headless server, I need the possibility to access it early via serial console. I have enabled the serial ports in the BIOS and they show up in Linux as /dev/ttyS0 and /dev/ttyS1, on 0x3f8/IRQ 4 and 0x2f8/IRQ 3 respectively.

But any attempt to read or write just turns up... nothing. I checked that my RS323 breakout cable has the correct wiring/pin configuration, that is not the issue. Even when I directly connect the RX to the TX pin on the motherboard (essentially looping back all data I send immediately), nothing will be received. My commandline-fu definitely is correct because when I use an USB-to-serial-adapter (/dev/ttyUSB0) and connect RX and TX pins on the very same machine, then I get exactly back what I send.

On the net I find the info that in the past, many Asrock boards seem to have needed a BIOS update to get the serial port working. So perhaps this was overlooked when the boards shipped, since serial connections are mostly unused? I'm at version 1.20 of the BIOS.