Plane: Only resend the mixer configuration if its changed

ArduPlane/Plane.h

@@ -721,6 +721,11 @@ private:
     // support for quadcopter-plane
     QuadPlane quadplane{ahrs};
 
+#if CONFIG_HAL_BOARD == HAL_BOARD_PX4
+    // the crc of the last created PX4Mixer
+    int32_t last_mixer_crc = -1;
+#endif // CONFIG_HAL_BOARD
+    
     void demo_servos(uint8_t i);
     void adjust_nav_pitch_throttle(void);
     void update_load_factor(void);
@@ -864,7 +869,7 @@ private:
     void update_fbwb_speed_height(void);
     void setup_turn_angle(void);
     bool print_buffer(char *&buf, uint16_t &buf_size, const char *fmt, ...);
-    bool create_mixer(char *buf, uint16_t buf_size, const char *filename);
+    uint16_t create_mixer(char *buf, uint16_t buf_size, const char *filename);
     bool setup_failsafe_mixing(void);
     void set_control_channels(void);
     void init_rc_in();

ArduPlane/px4_mixer.cpp

@@ -21,6 +21,7 @@
 #include <drivers/drv_pwm_output.h>
 #include <systemlib/mixer/mixer.h>
 #include <modules/px4iofirmware/protocol.h>
+#include <GCS_MAVLink/include/mavlink/v1.0/checksum.h>
 
 #define PX4_LIM_RC_MIN 900
 #define PX4_LIM_RC_MAX 2100
@@ -44,9 +45,9 @@ bool Plane::print_buffer(char *&buf, uint16_t &buf_size, const char *fmt, ...)
 }
 
 /*
-  create a PX4 mixer buffer given the current fixed wing parameters
+  create a PX4 mixer buffer given the current fixed wing parameters, returns the size of the buffer used
  */
-bool Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
+uint16_t Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
 {
     char *buf0 = buf;
     uint16_t buf_size0 = buf_size;
@@ -125,7 +126,7 @@ bool Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
         } else {
             // a empty output
             if (!print_buffer(buf, buf_size, "Z:\n")) {
-                return false;
+                return 0;
             }
             continue;
         }
@@ -169,7 +170,7 @@ bool Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
                               in_scale_high,
                               0,
                               -limit, limit)) {
-                return false;
+                return 0;
             }
         } else {
             const RC_Channel *chan1 = RC_Channel::rc_channel(c1);
@@ -184,7 +185,7 @@ bool Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
             // of the PX4IO input processing
             if (!print_buffer(buf, buf_size, "M: 2\n") ||
                 !print_buffer(buf, buf_size, "O: %d %d 0 %d %d\n", mix, mix, (int)-scale_max1, (int)scale_max1)) {
-                return false;
+                return 0;
             }
             int32_t in_scale_low = pwm_scale*(chan1_trim - pwm_min);
             int32_t in_scale_high = pwm_scale*(pwm_max - chan1_trim);
@@ -192,7 +193,7 @@ bool Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
             if (!print_buffer(buf, buf_size, "S: 0 %u %d %d %d %d %d\n", 
                               c1, in_scale_low, in_scale_high, offset,
                               (int)-scale_max2, (int)scale_max2)) {
-                return false;
+                return 0;
             }
             in_scale_low = pwm_scale*(chan2_trim - pwm_min);
             in_scale_high = pwm_scale*(pwm_max - chan2_trim);
@@ -201,13 +202,13 @@ bool Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
                 if (!print_buffer(buf, buf_size, "S: 0 %u %d %d %d %d %d\n", 
                                   c2, in_scale_low, in_scale_high, offset,
                                   (int)-scale_max2, (int)scale_max2)) {
-                    return false;
+                    return 0;
                 }
             } else {
                 if (!print_buffer(buf, buf_size, "S: 0 %u %d %d %d %d %d\n", 
                                   c2, -in_scale_low, -in_scale_high, -offset,
                                   (int)-scale_max2, (int)scale_max2)) {
-                    return false;
+                    return 0;
                 }
             }
         }
@@ -221,7 +222,7 @@ bool Plane::create_mixer(char *buf, uint16_t buf_size, const char *filename)
         write(mix_fd, buf0, buf_size0 - buf_size);
         close(mix_fd);
     }
-    return true;
+    return buf_size0 - buf_size;
 }
 
 
@@ -240,12 +241,21 @@ bool Plane::setup_failsafe_mixing(void)
         return false;
     }
 
-    if (!create_mixer(buf, buf_size, mixer_filename)) {
+    uint16_t fileSize = create_mixer(buf, buf_size, mixer_filename);
+    if (!fileSize) {
         hal.console->printf("Unable to create mixer\n");
         free(buf);
         return false;
     }
 
+    uint16_t new_crc = crc_calculate((uint8_t *)buf, fileSize);
+
+    if ((int32_t)new_crc == last_mixer_crc) {
+        return true;
+    } else {
+        last_mixer_crc = new_crc;
+    }
+
     enum AP_HAL::Util::safety_state old_state = hal.util->safety_switch_state();
     struct pwm_output_values pwm_values = {.values = {0}, .channel_count = 8};