How can i use the attach interupt command and read rc channels in background. I am in doubt that attach interupt is only applied to 2 pins just and cant be used to get data from other pins.
I am not sure what you are asking but you can have as many interrupt sources on a single interrupt pin as you want. When the interrupt happens in your ISR (Interrupt Service Routine) you simply check each one and process the ones that are valid. Be sure to do one final check before exiting as another could happen while servicing the first one.