How to enable UART? (ubuntu_lxde_desktop)

[Fireworks]

I don't use any uart port ttyS1, ttyS2, ttyS3 on ubuntu_lxde_desktop_OrangePipcplus_v0_9_1.img os on OrangePiPcPlus board.

I Used some software as minicom, gtkterm .. but don't anything happen on TDX, RTX pin.

when run command line folow

$ gpio readall

 

Help me please.

Edited March 20, 2018 by chwe
splittend and moved to p2p cause not related to armbian

[martinayotte]

Any UARTs other than ttyS0 need to be explicitly enabled either by editing FEX or DT, depending if kernel is Legacy or Mainline.