ArduPPM: throttle failsafe is now triggered on single channel loss but recovery from the throttle low is possible

Tools/ArduPPM/ATMega328p/Encoder-PPM.c

@@ -35,11 +35,12 @@
 //	0.9.85 : Added brownout reset detection flag
 //	0.9.86 : Added a #define to disable Radio Passthrough mode (hardware failsafe for Arduplane)
 //	0.9.87 : #define correction for radio passthrough (was screwed up).
+//  0.9.88 : LED fail-safe indication is on whenever throttle is low
 // ------------------------------------------------------------------------------------------------------------------------------------------------------------
 // PREPROCESSOR DIRECTIVES
 // ------------------------------------------------------------------------------------------------------------------------------------------------------------
 
-#include "..\Libraries\PPM_Encoder.h"
+#include "../Libraries/PPM_Encoder.h"
 #include <util/delay.h>
 
 
@@ -47,7 +48,7 @@
 #define ERROR_DETECTION_WINDOW	3000 * LOOP_TIMER_10MS			// Detection window for error detection (default to 30s)
 #define	ERROR_CONDITION_DELAY	500 * LOOP_TIMER_10MS			// Servo error condition LED delay (LED blinking duration)
 
-#define PASSTHROUGH_MODE_ENABLED	// Comment this line to remove CH8 radio passthrough mode support (hardware failsafe for Arduplane)
+//#define PASSTHROUGH_MODE_ENABLED	// Comment this line to remove CH8 radio passthrough mode support (hardware failsafe for Arduplane)
 #define PASSTHROUGH_CHANNEL		8 * 2	// Channel for passthrough mode selection
 #define PASSTHROUGH_CHANNEL_OFF_US		ONE_US * 1600 - PPM_PRE_PULSE	// Passthrough off threshold
 #define PASSTHROUGH_CHANNEL_ON_US		ONE_US * 1800 - PPM_PRE_PULSE	// Passthrough on threshold
@@ -283,7 +284,7 @@ int main(void)
 	// ------------------------------------------------------------------------------
 	while( 1 )
 	{
-		if ( servo_error_condition || servo_input_missing )	// We have an error 
+		if ( throttle_failsafe_force )	// We have an error 
 		{
 			blink_led ( 6 * LOOP_TIMER_10MS ); // Status LED very fast blink if invalid servo input or missing signal
 		}
@@ -368,7 +369,8 @@ int main(void)
 		// ------------------------------------------------------------------------------
 		// Status LED control
 		// ------------------------------------------------------------------------------
-		if ( servo_error_condition || servo_input_missing )	// We have an error 
+
+		if ( throttle_failsafe_force ) // We have an error 
 		{
 			blink_led ( 6 * LOOP_TIMER_10MS ); // Status LED very fast blink if invalid servo input or missing signal
 		}
@@ -454,7 +456,7 @@ int main(void)
 		// Status LED control
 		// ------------------------------------------------------------------------------
 		
-		if ( servo_input_missing )	// We have an error 
+		if ( throttle_failsafe_force )	// We have an error 
 		{
 			blink_led ( 6 * LOOP_TIMER_10MS ); // Status LED very fast blink if invalid servo input or missing signal
 		}

Tools/ArduPPM/Libraries/PPM_Encoder.h

@@ -1,5 +1,5 @@
 // -------------------------------------------------------------
-// ArduPPM (PPM Encoder) V2.3.13
+// ArduPPM (PPM Encoder) V2.3.14pre
 // -------------------------------------------------------------
 // Improved servo to ppm for ArduPilot MEGA v1.x (ATmega328p),
 // PhoneDrone and APM2.x (ATmega32u2)
@@ -127,6 +127,12 @@
 // V2.3.13 - Official release
 //         - Fail-safe vales changed back to normal fail-safe values. Use until APM code knows how to handle lost channel signal (800us)
 
+// 16-12-2012
+// V2.3.14pre - Internal test release
+//            - If one or more or all channel(s) are disconnected, throttle is set to fail-safe low (RTL)
+//            - If the misssing channel(s) are regained, throttle control is regained
+
+
 // -------------------------------------------------------------
 
 #ifndef _PPM_ENCODER_H_
@@ -168,7 +174,7 @@
 #endif
 
 // Version stamp for firmware hex file ( decode hex file using <avr-objdump -s file.hex> and look for "ArduPPM" string )
-const char ver[15] = "ArduPPMv2.3.13"; 
+const char ver[15] = "ArduPPMv2.3.14pre"; 
 
 // -------------------------------------------------------------
 // INPUT MODE
@@ -322,6 +328,9 @@ volatile uint8_t ppm_timeout[ PPM_ARRAY_MAX ];
 #define SERVO_INPUT_CONNECTED_VALUE 100
 volatile uint8_t servo_input_connected[ PPM_ARRAY_MAX ];
 
+// count the channels which have been once connected but then got disconnected
+volatile uint8_t disconnected_channels;
+
 // AVR parameters for PhoneDrone and APM2 boards using ATmega32u2
 #if defined (__AVR_ATmega16U2__) || defined (__AVR_ATmega32U2__)
 
@@ -413,6 +422,8 @@ volatile bool ppm_generator_active = false;
 // Used to indicate a brownout restart
 volatile bool brownout_reset = false;
 
+// Used to force throttle fail-safe mode (RTL)
+volatile bool throttle_failsafe_force = false;
 
 // ------------------------------------------------------------------------------
 // PPM GENERATOR START - TOGGLE ON COMPARE INTERRUPT ENABLE
@@ -655,8 +666,18 @@ CHECK_PINS_LOOP: // Input servo pin check loop
                 servo_input_connected[ ppm_channel ]++;
             }
             
-           //Reset ppm single channel fail-safe timeout
+            //Reset ppm single channel fail-safe timeout
             ppm_timeout[ ppm_channel ] = 0;
+
+            // Check for forced throttle fail-safe
+            if( throttle_failsafe_force )
+            {
+                if( ppm_channel == 5 )
+                {
+                    // Force throttle fail-safe
+                    servo_width = PPM_THROTTLE_FAILSAFE;
+                }
+            }
     
         #ifdef _AVERAGE_FILTER_
             // Average filter to smooth input jitter
@@ -754,6 +775,12 @@ ISR( PPM_INT_VECTOR, ISR_NOBLOCK )
         PPM_COMPARE += failsafe_ppm[ ppm_out_channel ];
         sei();
 
+        // Count the channel that we have lost
+        if( servo_input_connected[ ppm_out_channel ] )
+        {
+            disconnected_channels++;
+        }
+
     #if defined (__AVR_ATmega16U2__) || defined (__AVR_ATmega32U2__)
         // Turn on RX LED to indicate a fail-safe condition
         PORTD &= ~(1 << PD4);
@@ -777,6 +804,18 @@ ISR( PPM_INT_VECTOR, ISR_NOBLOCK )
     {
         ppm_out_channel = 0;
 
+		// Did we lose one or more active servo input channel? If so force throttle fail-safe (RTL)
+        if( disconnected_channels > 0 )
+        {
+            throttle_failsafe_force = true;
+        }
+        else
+        {
+            throttle_failsafe_force = false;
+        }
+
+        disconnected_channels = 0;
+
         #if defined (__AVR_ATmega16U2__) || defined (__AVR_ATmega32U2__)
         // Blink TX LED when PPM generator has finished a pulse train
         PIND |= ( 1<< PD5 );