AP_HAL: Add test sketch for RC input to RC output pass through

libraries/AP_HAL/examples/RCInputToRCOutput/Makefile

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+include ../../../../mk/apm.mk

libraries/AP_HAL/examples/RCInputToRCOutput/RCInputToRCOutput.pde

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+/*
+    RC input pass trough to RC output
+    Max RC channels 14
+    Max update rate 10 Hz
+*/
+
+#include <AP_HAL.h>
+#include <AP_HAL_AVR.h>
+#include <AP_HAL_AVR_SITL.h>
+#include <AP_HAL_PX4.h>
+#include <AP_HAL_Linux.h>
+#include <AP_HAL_Empty.h>
+#include <AP_Common.h>
+#include <AP_Baro.h>
+#include <AP_ADC.h>
+#include <AP_GPS.h>
+#include <AP_InertialSensor.h>
+#include <AP_Notify.h>
+#include <DataFlash.h>
+#include <GCS_MAVLink.h>
+#include <AP_Mission.h>
+#include <StorageManager.h>
+#include <AP_Terrain.h>
+#include <AP_Compass.h>
+#include <AP_Declination.h>
+#include <SITL.h>
+#include <Filter.h>
+#include <AP_Param.h>
+#include <AP_Progmem.h>
+#include <AP_Math.h>
+#include <AP_AHRS.h>
+#include <AP_Airspeed.h>
+#include <AP_Vehicle.h>
+#include <AP_ADC_AnalogSource.h>
+#include <AP_NavEKF.h>
+#include <AP_Rally.h>
+#include <AP_Scheduler.h>
+#include <UARTDriver.h>
+#include <AP_BattMonitor.h>
+
+const AP_HAL::HAL& hal = AP_HAL_BOARD_DRIVER;
+
+#define MAX_CHANNELS 14
+
+static uint8_t max_channels = 0;
+static uint16_t last_value[MAX_CHANNELS];
+
+void setup(void) 
+{
+    hal.console->printf("Starting RCInputToRCOutput test\n");
+
+    for(uint8_t i = 0; i < MAX_CHANNELS; i++) {
+        hal.rcout->enable_ch(i);
+    }
+}
+
+void loop(void) 
+{
+    bool changed = false;
+    uint8_t nchannels = hal.rcin->num_channels();
+
+    if(nchannels > MAX_CHANNELS) {
+       nchannels = MAX_CHANNELS;
+    }
+
+    for(uint8_t i = 0; i < nchannels; i++) {
+        uint16_t v = hal.rcin->read(i);
+        if(last_value[i] != v) {
+            hal.rcout->write(i, v);
+            changed = true;
+            last_value[i] = v;
+        }
+        if(i > max_channels) {
+            max_channels = i;
+        }
+    }
+    if(changed) {
+        for(uint8_t i = 0; i < max_channels; i++) {
+            hal.console->printf("%2u:%04u ", (unsigned)i + 1, (unsigned)last_value[i]);
+        }
+        hal.console->println();
+    }
+    hal.scheduler->delay(100);
+}
+
+AP_HAL_MAIN();