Author: Natanji
Subject: Serial Ports (COM1/COM2) not working on J3455M
Posted: 06 Jan 2017 at 7:18am
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.
Edited by Natanji - 19 minutes ago at 7:31am
Subject: Serial Ports (COM1/COM2) not working on J3455M
Posted: 06 Jan 2017 at 7:18am
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.
Edited by Natanji - 19 minutes ago at 7:31am
