AP_Logger: log default param values

libraries/AP_Logger/AP_Logger.cpp

@@ -865,7 +865,7 @@ void AP_Logger::Write_Mode(uint8_t mode, const ModeReason reason)
 
 void AP_Logger::Write_Parameter(const char *name, float value)
 {
-    FOR_EACH_BACKEND(Write_Parameter(name, value));
+    FOR_EACH_BACKEND(Write_Parameter(name, value, quiet_nanf()));
 }
 
 void AP_Logger::Write_Mission_Cmd(const AP_Mission &mission,

libraries/AP_Logger/AP_Logger_Backend.h

@@ -128,10 +128,11 @@ public:
     bool Write_Mission_Cmd(const AP_Mission &mission,
                                const AP_Mission::Mission_Command &cmd);
     bool Write_Mode(uint8_t mode, const ModeReason reason);
-    bool Write_Parameter(const char *name, float value);
+    bool Write_Parameter(const char *name, float value, float default_val);
     bool Write_Parameter(const AP_Param *ap,
                              const AP_Param::ParamToken &token,
-                             enum ap_var_type type);
+                             enum ap_var_type type,
+                             float default_val);
     bool Write_VER();
 
     uint32_t num_dropped(void) const {

libraries/AP_Logger/LogFile.cpp

@@ -103,13 +103,14 @@ bool AP_Logger_Backend::Write_Format_Units(const struct LogStructure *s)
 /*
   write a parameter to the log
  */
-bool AP_Logger_Backend::Write_Parameter(const char *name, float value)
+bool AP_Logger_Backend::Write_Parameter(const char *name, float value, float default_val)
 {
     struct log_Parameter pkt{
         LOG_PACKET_HEADER_INIT(LOG_PARAMETER_MSG),
         time_us : AP_HAL::micros64(),
         name  : {},
-        value : value
+        value : value,
+        default_value : default_val
     };
     strncpy_noterm(pkt.name, name, sizeof(pkt.name));
     return WriteCriticalBlock(&pkt, sizeof(pkt));
@@ -120,11 +121,12 @@ bool AP_Logger_Backend::Write_Parameter(const char *name, float value)
  */
 bool AP_Logger_Backend::Write_Parameter(const AP_Param *ap,
                                             const AP_Param::ParamToken &token,
-                                            enum ap_var_type type)
+                                            enum ap_var_type type,
+                                            float default_val)
 {
     char name[16];
     ap->copy_name_token(token, &name[0], sizeof(name), true);
-    return Write_Parameter(name, ap->cast_to_float(type));
+    return Write_Parameter(name, ap->cast_to_float(type), default_val);
 }
 
 // Write an RCIN packet

libraries/AP_Logger/LogStructure.h

@@ -205,6 +205,7 @@ struct PACKED log_Parameter {
     uint64_t time_us;
     char name[16];
     float value;
+    float default_value;
 };
 
 struct PACKED log_DSF {
@@ -920,6 +921,7 @@ struct PACKED log_VER {
 // @Field: TimeUS: Time since system startup
 // @Field: Name: parameter name
 // @Field: Value: parameter value
+// @Field: Default: default parameter value for this board and config
 
 // @LoggerMessage: PIDR,PIDP,PIDY,PIDA,PIDS,PIDN,PIDE
 // @Description: Proportional/Integral/Derivative gain values for Roll/Pitch/Yaw/Altitude/Steering
@@ -1213,7 +1215,7 @@ struct PACKED log_VER {
     { LOG_MULT_MSG, sizeof(log_Format_Multiplier), \
       "MULT", "Qbd",      "TimeUS,Id,Mult", "s--","F--" },   \
     { LOG_PARAMETER_MSG, sizeof(log_Parameter), \
-     "PARM", "QNf",        "TimeUS,Name,Value", "s--", "F--"  },       \
+     "PARM", "QNff",        "TimeUS,Name,Value,Default", "s---", "F---"  },       \
 LOG_STRUCTURE_FROM_GPS \
     { LOG_MESSAGE_MSG, sizeof(log_Message), \
       "MSG",  "QZ",     "TimeUS,Message", "s-", "F-"}, \

libraries/AP_Logger/LoggerMessageWriter.cpp

@@ -50,7 +50,8 @@ void LoggerMessageWriter_DFLogStart::reset()
     _next_unit_to_send = 0;
     _next_multiplier_to_send = 0;
     _next_format_unit_to_send = 0;
-    ap = AP_Param::first(&token, &type);
+    param_default = AP::logger().quiet_nanf();
+    ap = AP_Param::first(&token, &type, &param_default);
 }
 
 bool LoggerMessageWriter_DFLogStart::out_of_time_for_writing_messages() const
@@ -87,10 +88,11 @@ void LoggerMessageWriter_DFLogStart::process()
 
     case Stage::PARMS:
         while (ap) {
-            if (!_logger_backend->Write_Parameter(ap, token, type)) {
+            if (!_logger_backend->Write_Parameter(ap, token, type, param_default)) {
                 return;
             }
-            ap = AP_Param::next_scalar(&token, &type);
+            param_default = AP::logger().quiet_nanf();
+            ap = AP_Param::next_scalar(&token, &type, &param_default);
         }
 
         _params_done = true;

libraries/AP_Logger/LoggerMessageWriter.h

@@ -140,6 +140,7 @@ private:
 
     AP_Param::ParamToken token;
     AP_Param *ap;
+    float param_default;
     enum ap_var_type type;