Moxa serial (mxser) Linux driver and tools modified for latest kernels (supported kernel 5.11 and above). Intended for CP-1XX and other MOXA multiport serial RS232/485 boards Based on original Moxa Linux kernel 5.x.x drivers (09/02/2019)

You should disable old SmartIO (mxser) drivers in kernel tree

  │ Symbol: MOXA_SMARTIO 
  │   Prompt: Moxa SmartIO support v. 2.0 
  │   Location:  
  │     -> Device Drivers
  │       -> Character devices  
  │           -> Non-standard serial port support

Driver install (mxupcie, mxser)

make mxser 
make driver_install

Configuration tool install (muestty)

cd utility/conf
make 
make install

Load kernel module for PCIe MOXA card

modprobe mxupcie

Configure port

Set 2 wire RS485 mode on port 0

muestty -i RS4852W /dev/ttyMUE0

Enable termination resistor on port 3

muestty -t 120TERM /dev/ttyMUE3

See original readme.txt for more information