3 x rs232 tasks

Hi all ! Someone could help me with three rs232 tasks ? rs232_1 – used for modbus slave (rtu frames), interfacig with a human machine interface (always running) rs232_2 – interface with a rfid reader (sometimes rfid sends a frame for my board) rs_232_3 – at commands to a gsm modem (interval = 2 seconds). I have to receive the answer of that. How to define this tasks ? Thanks in advance William.

3 x rs232 tasks

Well… The question is … You have to write three task. How much interfaces do you have ?