ardupilot/libraries/APM_RC/examples/APM1_radio/APM1_radio.pde

/*
	Example of APM_RC library.
	Code by Jordi MuÒoz and Jose Julio. DIYDrones.com

	Print Input values and send Output to the servos
	(Works with last PPM_encoder firmware)
*/

#include <Arduino_Mega_ISR_Registry.h>
#include <APM_RC.h> // ArduPilot Mega RC Library

Arduino_Mega_ISR_Registry isr_registry;
APM_RC_APM1 APM_RC;

void setup()
{
    isr_registry.init();
	APM_RC.Init(&isr_registry);	 // APM Radio initialization

	Serial.begin(115200);
	Serial.println("ArduPilot Mega RC library test");
	delay(1000);
}

void loop()
{
	// New radio frame? (we could use also if((millis()- timer) > 20)
	if (APM_RC.GetState() == 1){
		Serial.print("CH:");
		for(int i = 0; i < 8; i++){
			Serial.print(APM_RC.InputCh(i));	// Print channel values
			Serial.print(",");
			APM_RC.OutputCh(i, APM_RC.InputCh(i)); // Copy input to Servos
		}
		Serial.println();
	}
}