DataFlash: include sample count in ISBH

libraries/DataFlash/DataFlash.cpp

@@ -711,6 +711,7 @@ bool DataFlash_Class::Log_Write_ISBH(const uint16_t seqno,
                                      const AP_InertialSensor::IMU_SENSOR_TYPE sensor_type,
                                      const uint8_t sensor_instance,
                                      const uint16_t multiplier,
+                                     const uint16_t sample_count,
                                      const uint64_t sample_us,
                                      const float sample_rate_hz)
 {
@@ -724,6 +725,7 @@ bool DataFlash_Class::Log_Write_ISBH(const uint16_t seqno,
         sensor_type    : (uint8_t)sensor_type,
         instance       : sensor_instance,
         multiplier     : multiplier,
+        sample_count   : sample_count,
         sample_us      : sample_us,
         sample_rate_hz : sample_rate_hz,
     };

libraries/DataFlash/DataFlash.h

@@ -112,6 +112,7 @@ public:
                         AP_InertialSensor::IMU_SENSOR_TYPE sensor_type,
                         uint8_t instance,
                         uint16_t multiplier,
+                        uint16_t sample_count,
                         uint64_t sample_us,
                         float sample_rate_hz);
     bool Log_Write_ISBD(uint16_t isb_seqno,

libraries/DataFlash/LogStructure.h

@@ -114,6 +114,7 @@ struct PACKED log_ISBH {
     uint8_t sensor_type; // e.g. GYRO or ACCEL
     uint8_t instance;
     uint16_t multiplier;
+    uint16_t sample_count;
     uint64_t sample_us;
     float sample_rate_hz;
 };
@@ -965,8 +966,8 @@ struct PACKED log_DSTL {
 #define IMT_LABELS "TimeUS,DelT,DelvT,DelaT,DelAX,DelAY,DelAZ,DelVX,DelVY,DelVZ"
 #define IMT_FMT    "Qfffffffff"
 
-#define ISBH_LABELS "TimeUS,N,type,instance,mul,SampleUS,smp_rate"
+#define ISBH_LABELS "TimeUS,N,type,instance,mul,smp_cnt,SampleUS,smp_rate"
-#define ISBH_FMT    "QHBBHQf"
+#define ISBH_FMT    "QHBBHHQf"
 
 #define ISBD_LABELS "TimeUS,N,seqno,x,y,z"
 #define ISBD_FMT    "QHHaaa"