Jetson Xavier NX unreadable pyserial (usb)

I have 2 devices connected to Weighting terminal CAS-CI200A via RS-232:

  • Lenovo notebook with Kubuntu 20.04 (x86_64 architecture)
  • Jetson Xavier NX with Ubuntu 18.04 LTS, JetPack 4.5 (aarch64 architecture)
 import serial
    ser = serial.Serial(
    line = ser.readline()

Result of the same pyserial library for both devices is:

  • for Lenovo: b'ERR 13\r\n'
  • for Jetson: b'\x05\x1f\x12\x1f\x12\x1f\x1e\x1e\x0c\x06\r\n'

Also I try to use: cat /dev/ttyUSB0 results are the same.

Task is to get b'ERR 13\r\n' from Jetson.

I try to .decode() the line b'\x05\x1f\x12\x1f\x12\x1f\x1e\x1e\x0c\x06\r\n', but still no success:

Screenshot from 2021-06-30 12-27-20

The only difference between the devises is architecture and OS version, the library and the code are the same.

Does anyone know the way to get correct response?

Is this an actual 9-pin D-sub connector? If so, then the PHY voltages are wrong. This must be a 3.3V TTL level device (same protocol as RS-232, but different voltage levels).

We use 9 pin D-sub RS232 to USB converter like this:

The voltage on usb power is 5.0 V
The voltage on usb signal is 2.9 V

We found recommendation about usb process priority&governors: link.
Could you explain how to change process priority / USB power settings on Jetson Xavier (Jetpack)

The 9 pin D-sub you have could damage the Jetson, and is not suitable for use directly with the Jetson’s serial UARTs (you would have to use level converter hardware). You must use a 3.3V unit. Examples:

Note that none of these use a 9-pin D-sub. All also have a spec of 3.3V. The 9-pin interface is the wrong PHY.

I don’t connect usb to 9 pin D-sub directly, I use converter (cable on image) which base on chip PL2303SA. Also the same cable, as I wrote previously, work perfectly on laptop (Kubuntu 20.04).

Found solution.

Problem was in converter’s driver(parity not work)
1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter

The solution is to update driver.

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