Hi @RobertCNelson
Good to hear from you again 
I have the manual.
I have a simple Qt program running on Linux using /dev/ttyS0 which i cross compile with /dev/tty1 (i presume UART1 as tty1). it does not communicate at all. Do DTE Mode & DCE Mode affect the communication? As I need all 3 ports behave just like “Standard” RS232.
UART 1 and UART 3 should be able to use directly with any devices? Do I need to connect RTS and CTS? I had tried only 3 wire connection (RX,TX and GND) with Utek UT-2216 RS232 to RS485 Active Serial Interface converter by using “/dev/tty1”.
As for UART 5, I will purchase the recommended unit (all 6 lines required ?)
Any Idea as I am not using flow control.
Regards
Simon
PS: Thanks for all the help. I hope all this will work out then I may proceed to purchase Digi SBC for Production from DigiKey.