/dev/ttyTHS1 RX working but TX not

/dev/ttyTHS1 RX working but TX not.
I have disabled nvgetty and do system update and upgrade.
I have replace a new jetson nano and still can not send data through RX pin 8.
I have confirmed that both jetson and arduino ttl voltage is 3.3v.
I alse tried minicom to observe.
Jetson Nano RX,TX,GND <==> Esp8266 TX,RX,GND
Even Jetson Nano RX <==> Self TX has no response too.
Is there anything that I mismatched? Please help me. Thanks.
My python code runs as root:

class MCUControl(threading.Thread, metaclass=Singleton):
	def __init__(self):
		self.closed = False
		self.ser = serial.Serial('/dev/ttyTHS1', 115200)
		self.sendlock = threading.RLock()
	def run(self,*args,**kwargs):
		while not self.closed:
			if self.ser.isOpen():
				data = self.ser.readline()
				data = data.strip().decode()
				if data:
				self.send('d,660') # NO RESPONSE ON ARDUINO
	def send(self, cmd):
		cmd += "\n"
		with self.sendlock:
	def stop(self):
		self.closed = True

system version: JP 4.2.3

Make sure all sides of the connection are using the same flow control, e.g., software only, or CTS/DTS. If half works and the other does not, then perhaps one side is expecting flow control.

I have checked both sides have no soft/hardware flow control.
I connect nano rx and tx, but rx can’t receive any char.
The /dev/ttyUSB0 is working while using a usb ttl adapter CH340.

Tonight I was able to do serial communication on J41 and J44 simultaneously with a Teensy board (an Arduino-like microcontroller). I use the J44 UART (/dev/ttyTHS0) as a serial console to send commands from the Teensy to the Jetson Nano (to start a program in the Nano), then use the J41 UART (/dev/ttyTHS1) to stream object detection data to the Teensy. I do this with C/C++ code - the python version should work too.

To the Nvidia people, is there a way to bypass the login prompt that comes up from the serial console?

I gave up. CH340 is working, and I have migrated to this solution. Maybe Jetson Nano has some bugs in communication between serial ttyTHS1