I have used serial device using RS232 communication. I want to check signal of device. When I push its button, I can get Hexa data (After I will say signal). My computer has 4 serial ports (main board: asrock IMB-183), so I want to connect serial to device. When I test the device using USB2SERIAL, I can get the signal with minicom. But when I use serial port, minicom does not work.

I checked the Rx, Tx using Windows (same computer and same device) with serial at terminal program (like highper terminal), I can get the signal. So I think I have problem with Linux together with using serial port.

I checked my BIOS. At SuperI/O I turned on COM port to enable. and I checked group, dialout.

Now I show you status of my computer and device.

 # id
......, 20(dialout), .......

 # cat /proc/tty/driver/serial
serinfo : 1.0 driver revision:
0: uart : 16550A port : 000003F8 irq: 4 tx:0 rx:0 RTS|DTR
1: uart : 16550A port : 000002F8 irq: 3 tx:0 rx:0 RTS|DTR

linux 3.13.0-32-generic, Ubuntu 12.04

  • Can you try to catch the device output by using cat /dev/ttyS0 command? The number here is the port number, test it from 0 - 3 if you have 4 ports. – P.-H. Lin Feb 7 '17 at 7:17
  • I check all port to cat/dev/ttyS*, but all port do show anything else. – 오찬민 Feb 7 '17 at 7:39
  • Try screen /dev/ttyS0, you can find more instructions here: Working with the serial console, I would say it's better to check if the serial port works on your system, search "RS-232 loopback". Or if you happen to have a COM-to-COM connector, connect it with another system that has a working serial port and test some simple TX/RX with echo / screen command on them. – P.-H. Lin Feb 7 '17 at 9:28
  • to P.-H. Lin, I checked all hardware included RS-232 loopback at windows. all of port is ok. but when i boot with ubuntu, Serial port dosen't work. But!!!! now I found something that ttyS0 is work. and check echo / cat command is ok. but others not work. – 오찬민 Feb 7 '17 at 11:39

As you mentioned that all ports work on Windows but not Ubuntu, maybe you can try to use a newer kernel (A 16.04 / 16.10 LiveUSB will do) to see if it can make other ports work.

Anyway, at least it seems that your ttyS0 is working with echo / cat command. The last thing I can suggest is that if you still can't get any signal from you serial device, try to use stty command to change the baud rate:

sudo stty -F /dev/ttyS0  # Print current setting
sudo stty -F /dev/ttyS0 9600  # Set the baud rate

9600 here should be replaced with the correct baud rate.

More information about stty command can be found here.

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