AP_RCProtocol: improved reliability of DSM vs SRXL detection

base detection on framing, not including failsafe

libraries/AP_RCProtocol/AP_RCProtocol.cpp

@@ -63,8 +63,9 @@ void AP_RCProtocol::process_pulse(uint32_t width_s0, uint32_t width_s1)
             continue;
         }
         if (backend[i] != nullptr) {
+            uint32_t frame_count = backend[i]->get_rc_frame_count();
             backend[i]->process_pulse(width_s0, width_s1);
-            if (backend[i]->new_input()) {
+            if (frame_count != backend[i]->get_rc_frame_count()) {
                 _good_frames[i]++;
                 if (requires_3_frames((rcprotocol_t)i) && _good_frames[i] < 3) {
                     continue;
@@ -74,6 +75,7 @@ void AP_RCProtocol::process_pulse(uint32_t width_s0, uint32_t width_s1)
                 memset(_good_frames, 0, sizeof(_good_frames));
                 _last_input_ms = now;
                 _detected_with_bytes = false;
+                break;
             }
         }
     }
@@ -123,8 +125,9 @@ void AP_RCProtocol::process_byte(uint8_t byte, uint32_t baudrate)
     // otherwise scan all protocols
     for (uint8_t i = 0; i < AP_RCProtocol::NONE; i++) {
         if (backend[i] != nullptr) {
+            uint32_t frame_count = backend[i]->get_rc_frame_count();
             backend[i]->process_byte(byte, baudrate);
-            if (backend[i]->new_input()) {
+            if (frame_count != backend[i]->get_rc_frame_count()) {
                 _good_frames[i]++;
                 if (requires_3_frames((rcprotocol_t)i) && _good_frames[i] < 3) {
                     continue;
@@ -134,6 +137,7 @@ void AP_RCProtocol::process_byte(uint8_t byte, uint32_t baudrate)
                 memset(_good_frames, 0, sizeof(_good_frames));
                 _last_input_ms = now;
                 _detected_with_bytes = true;
+                break;
             }
         }
     }

libraries/AP_RCProtocol/AP_RCProtocol_Backend.cpp

@@ -52,6 +52,7 @@ void AP_RCProtocol_Backend::add_input(uint8_t num_values, uint16_t *values, bool
     num_values = MIN(num_values, MAX_RCIN_CHANNELS);
     memcpy(_pwm_values, values, num_values*sizeof(uint16_t));
     _num_channels = num_values;
+    rc_frame_count++;
     if (!in_failsafe) {
         rc_input_count++;
     }

libraries/AP_RCProtocol/AP_RCProtocol_Backend.h

@@ -39,13 +39,20 @@ public:
         PARSE_TYPE_SIGREAD,
         PARSE_TYPE_SERIAL
     };
+
+    // get number of frames, ignoring failsafe
+    uint32_t get_rc_frame_count(void) const {
+        return rc_frame_count;
+    }
+
 protected:
     void add_input(uint8_t num_channels, uint16_t *values, bool in_failsafe);
 
 private:
     AP_RCProtocol &frontend;
-    unsigned int rc_input_count;
-    unsigned int last_rc_input_count;
+    uint32_t rc_input_count;
+    uint32_t last_rc_input_count;
+    uint32_t rc_frame_count;
 
     uint16_t _pwm_values[MAX_RCIN_CHANNELS];
     uint8_t  _num_channels;