4 Uarts and 2 Ethernet possiblities

[richardk]

Beware that you also need to control RTS for RS485 flow direction ...
If you don't want to bother with driver or this flow direction, you are better luck using a USB-RS485 dongle such as this one :
https://www.ebay.ca/itm/2PCS-CH340-USB-t...1911412433

thank you for reply.  I know about this pin for direction. In other forum (armbian) i saw yours post about using RTS signal for this. I have a allwiner board to but i can't find kernel module which support  uart  rts signal.  I know about usb-485 adapters whis is cheap but i do not have free usb ports..

RS485 might be difficult to control via software, if the speeds are high.

Actually, you might consider a Beaglebone Black or Green.  It has 5 UARTs available, and it can support RS485 with buffers (like the MAX485).  You can plug in a second Ethernet via USB.