RC_Channel: Add option bit for arming checking the throttle input (opt-in)

Also adds interface to find out what channel is used for rudder arming

libraries/RC_Channel/RC_Channel.h

@@ -330,6 +330,8 @@ public:
     // has_valid_input should be pure-virtual when Plane is converted
     virtual bool has_valid_input() const { return false; };
 
+    virtual RC_Channel *get_arming_channel(void) const { return nullptr; };
+
     bool gcs_overrides_enabled() const { return _gcs_overrides_enabled; }
     void set_gcs_overrides_enabled(bool enable) {
         _gcs_overrides_enabled = enable;
@@ -360,6 +362,14 @@ public:
         return _options & uint32_t(Option::LOG_DATA);
     }
     
+    bool arming_check_throttle() const {
+        return _options & uint32_t(Option::ARMING_CHECK_THROTTLE);
+    }
+
+    bool arming_skip_checks_rpy() const {
+        return _options & uint32_t(Option::ARMING_SKIP_CHECK_RPY);
+    }
+
     float override_timeout_ms() const {
         return _override_timeout.get() * 1e3f;
     }
@@ -371,14 +381,18 @@ public:
     */
     bool get_pwm(uint8_t channel, uint16_t &pwm) const;
 
+    uint32_t last_input_ms() const { return last_update_ms; };
+
 protected:
 
     enum class Option {
-        IGNORE_RECEIVER  = (1 << 0), // RC receiver modules
-        IGNORE_OVERRIDES = (1 << 1), // MAVLink overrides
-        IGNORE_FAILSAFE  = (1 << 2), // ignore RC failsafe bits
-        FPORT_PAD        = (1 << 3), // pad fport telem output
-        LOG_DATA         = (1 << 4), // log rc input bytes
+        IGNORE_RECEIVER       = (1 << 0), // RC receiver modules
+        IGNORE_OVERRIDES      = (1 << 1), // MAVLink overrides
+        IGNORE_FAILSAFE       = (1 << 2), // ignore RC failsafe bits
+        FPORT_PAD             = (1 << 3), // pad fport telem output
+        LOG_DATA              = (1 << 4), // log rc input bytes
+        ARMING_CHECK_THROTTLE = (1 << 5), // run an arming check for neutral throttle
+        ARMING_SKIP_CHECK_RPY = (1 << 6), // skip the an arming checks for the roll/pitch/yaw channels
     };
 
     void new_override_received() {
@@ -390,6 +404,7 @@ private:
     // this static arrangement is to avoid static pointers in AP_Param tables
     static RC_Channel *channels;
 
+    uint32_t last_update_ms;
     bool has_new_overrides;
 
     AP_Float _override_timeout;

libraries/RC_Channel/RC_Channels.cpp

@@ -74,6 +74,8 @@ bool RC_Channels::read_input(void)
 
     has_new_overrides = false;
 
+    last_update_ms = AP_HAL::millis();
+
     bool success = false;
     for (uint8_t i=0; i<NUM_RC_CHANNELS; i++) {
         success |= channel(i)->update();

libraries/RC_Channel/RC_Channels_VarInfo.h

@@ -86,7 +86,7 @@ const AP_Param::GroupInfo RC_Channels::var_info[] = {
     // @DisplayName: RC options
     // @Description: RC input options
     // @User: Advanced
-    // @Bitmask: 0:Ignore RC Receiver, 1:Ignore MAVLink Overrides, 2:Ignore Receiver Failsafe, 3:FPort Pad
+    // @Bitmask: 0:Ignore RC Receiver, 1:Ignore MAVLink Overrides, 2:Ignore Receiver Failsafe, 3:FPort Pad, 4:Log RC input bytes, 5:Arming check throttle for 0 input, 6:Skip the arming check for neutral Roll/Pitch/Yay sticks
     AP_GROUPINFO("_OPTIONS", 33, RC_CHANNELS_SUBCLASS, _options, 0),
 
     AP_GROUPEND