HAL_Linux: fixed a bug in RCInput::new_input

when a library called read() it would clear the new input flag, which
would cause new_input() in the main loop to return false. This could
trigger a false RC failsafe.

libraries/AP_HAL_Linux/RCInput.cpp

@@ -25,8 +25,7 @@ extern const AP_HAL::HAL& hal;
 
 using namespace Linux;
 
-RCInput::RCInput() :
-    new_rc_input(false)
+RCInput::RCInput()
 {
     ppm_state._channel_counter = -1;
 }
@@ -37,7 +36,11 @@ void RCInput::init()
 
 bool RCInput::new_input()
 {
-    return new_rc_input;
+    bool ret = rc_input_count != last_rc_input_count;
+    if (ret) {
+        last_rc_input_count = rc_input_count;
+    }
+    return ret;
 }
 
 uint8_t RCInput::num_channels()
@@ -47,7 +50,6 @@ uint8_t RCInput::num_channels()
 
 uint16_t RCInput::read(uint8_t ch)
 {
-    new_rc_input = false;
     if (_override[ch]) {
         return _override[ch];
     }
@@ -84,7 +86,7 @@ bool RCInput::set_override(uint8_t channel, int16_t override)
     if (channel < LINUX_RC_INPUT_NUM_CHANNELS) {
         _override[channel] = override;
         if (override != 0) {
-            new_rc_input = true;
+            rc_input_count++;
             return true;
         }
     }
@@ -112,7 +114,7 @@ void RCInput::_process_ppmsum_pulse(uint16_t width_usec)
                 _pwm_values[i] = ppm_state._pulse_capt[i];
             }
             _num_channels = ppm_state._channel_counter;
-            new_rc_input = true;
+            rc_input_count++;
         }
         ppm_state._channel_counter = 0;
         return;
@@ -143,7 +145,7 @@ void RCInput::_process_ppmsum_pulse(uint16_t width_usec)
             _pwm_values[i] = ppm_state._pulse_capt[i];
         }
         _num_channels = ppm_state._channel_counter;
-        new_rc_input = true;
+        rc_input_count++;
         ppm_state._channel_counter = -1;
     }
 }
@@ -221,7 +223,7 @@ void RCInput::_process_sbus_pulse(uint16_t width_s0, uint16_t width_s1)
             }
             _num_channels = num_values;
             if (!sbus_failsafe) {
-                new_rc_input = true;
+                rc_input_count++;
             }
         }
         goto reset;
@@ -291,7 +293,7 @@ void RCInput::_process_dsm_pulse(uint16_t width_s0, uint16_t width_s1)
                     _pwm_values[i] = values[i];
                 }
                 _num_channels = num_values;
-                new_rc_input = true;
+                rc_input_count++;
             }
         }
         memset(&dsm_state, 0, sizeof(dsm_state));
@@ -349,7 +351,7 @@ void RCInput::_update_periods(uint16_t *periods, uint8_t len)
         _pwm_values[i] = periods[i];
     }
     _num_channels = len;
-    new_rc_input = true;
+    rc_input_count++;
 }
 
 
@@ -408,7 +410,7 @@ bool RCInput::add_dsm_input(const uint8_t *bytes, size_t nbytes)
                 if (num_values > _num_channels) {
                     _num_channels = num_values;
                 }
-                new_rc_input = true;
+                rc_input_count++;
 #if 0
                 printf("Decoded DSM %u channels %u %u %u %u %u %u %u %u\n",
                        (unsigned)num_values,
@@ -444,7 +446,7 @@ bool RCInput::add_sumd_input(const uint8_t *bytes, size_t nbytes)
                 }
             }
             _num_channels = channel_count;
-            new_rc_input = true;
+            rc_input_count++;
             ret = true;
         }
         nbytes--;
@@ -474,7 +476,7 @@ bool RCInput::add_st24_input(const uint8_t *bytes, size_t nbytes)
                 }
             }
             _num_channels = channel_count;
-            new_rc_input = true;
+            rc_input_count++;
             ret = true;
         }
         nbytes--;
@@ -503,7 +505,7 @@ bool RCInput::add_srxl_input(const uint8_t *bytes, size_t nbytes)
             }
             _num_channels = channel_count;
             if (failsafe_state == false) {
-                new_rc_input = true;
+                rc_input_count++;
             }
             ret = true;
         }
@@ -564,7 +566,7 @@ void RCInput::add_sbus_input(const uint8_t *bytes, size_t nbytes)
                     _num_channels = num_values;
                 }
                 if (!sbus_failsafe) {
-                    new_rc_input = true;
+                    rc_input_count++;
                 }
 #if 0
                 printf("Decoded SBUS %u channels %u %u %u %u %u %u %u %u %s\n",

libraries/AP_HAL_Linux/RCInput.h

@@ -47,7 +47,8 @@ protected:
     void _process_rc_pulse(uint16_t width_s0, uint16_t width_s1);
     void _update_periods(uint16_t *periods, uint8_t len);
 
-    volatile bool new_rc_input;
+    volatile uint32_t rc_input_count;
+    uint32_t last_rc_input_count;
 
     uint16_t _pwm_values[LINUX_RC_INPUT_NUM_CHANNELS];
     uint8_t  _num_channels;

libraries/AP_HAL_Linux/RCInput_Multi.cpp

@@ -58,7 +58,7 @@ void RCInput_Multi::_timer_tick(void)
         if (inputs[i]->new_input()) {
             inputs[i]->read(_pwm_values, inputs[i]->num_channels());
             _num_channels = inputs[i]->num_channels();
-            new_rc_input = true;
+            rc_input_count++;
         }        
     }
 }