UART Port on J44 not working for Jetson Nano

Hi,

I wanted to use both the UART Ports available on the Jetson Nano (the one on J44 and the one on J41).
The UART Port on J41 works fine for bidirectional communication.

However the UART Port on J44 is not working to receive data on the Jetson from an external source.

When I use the pyserial library to establish communication, I get an error related to device already being possibly busy.
I think this is due to the agetty process running on ttyS0. But I am unable to kill this process.

I believe I need to disable the Serial Debug Console via Jetpack Installation for the Nano before flashing the Nano.
But I am not aware of the changes that need to be made after installation before flashing the Nano.

Can someone please advise what changes have to be done?

hello ritvik.ranadive,

could you please share your connections setups?
you might refer to below for setup Jetson-Nano serial console via J44.
thanks

https://youtu.be/xTwa0QBB0f0

Hi Jerry,

I tried the video suggested.
The connections are in the connections.jpg image
I then connect the other end to my computer’s USB port.

Screenshot from minicom terminal is in minicom.png
The terminal gets stuck at this stage and does not allow me to login.

The screenshot of the error is in error.png

My sender and receiver codes are given below.
The send.py code is being run on my computer and the receive.py code is being run on the Jetson Nano.

# send.py
import serial
ser = serial.Serial('/dev/ttyUSB0', 115200)
while(True):
    ser.write(b'hello\n')
# receive.py
import serial
ser = serial.Serial("/dev/ttyS0", 115200)
while True:
    x = ser.readline()
    print(x)



hello ritvik.ranadive,

the connection should be correct if you’re able to see the bootloader and kernel message through minicom terminal.

may I know what’s the addition I/O you had connected?
could you please narrow down the issue by disconnect all of them to check if the communication issue gone?
thanks

Hi JerryChang,

I removed all the other I/Os like HDMI Display, Keyboard, Ethernet etc.
But I still face the same issue while trying to connect using minicom.

The terminal gets stuck at login, it does not allow me to enter the login information.

Regards,
Ritvik

Hi ritvik,

Can you please try it other way?
Stop getty services.

  1. First connect on J44 (RX,Tx and GND), see minicom logs and login, then connect another UART on J41.
  2. start getty with the ttyTHS device:
    $sudo /sbin/getty -a ubuntu -L 115200 ttyTHSx &
    Here x is <1,2,3> mostly it will be 1
  3. This way, a new console will be available on tty port
    Identify which console is available just after running getty, Open that console using minicom.

Please provide me the steps used by you.

Thanks,
Shubhi