how to use UART3 to communicate

Hi all,

We tried to use ttyS2 as a UART connection port to communicate with fly control module, but we got some error message as below:

“ERROR: file descriptor /dev/ttyS2 is NOT a serial port”

My question is:

  1. is UART3 mounted as ttyS2 in default?
  2. if not, how can we mount it in kernel?
  3. is there any upper layer dev mounted for UART3?


I can’t answer, but what was it that said not a serial port? UART2 is connected to J3A2 header. I see this exists:


What do you get from:

sudo setserial -a /dev/ttyS2

Hi Sir,

I’m not sure why we got the error message like that, we used the command you provided and got the following message.

“/dev/ttyS2, Line2, UART: unknown, Port: 0x0000, IRQ: 0
Baud_base: 0, close_delay: 50, divisor: 0
closing_wait: 3000
Flags: spd_normal”

it seems that ttyS2 even doesn’t have IRQ

I don’t know if IRQ is an issue. What command is producing the message about “is NOT a serial port”? Have you set up anything for ttyS2 in “/etc/init/”?