Added restart/tare to API and various fixes

firmware/lib/session/SessionManager.h

@@ -13,6 +13,7 @@ public:
     void begin();
 
     void tare();
+    long tareOffset() const { return scale_.offset(); };
     void startMeasurements();
     void stopMeasurements();
     bool isMeasuring() const { return measuring_; }
@@ -51,6 +52,8 @@ SessionManager<SessionT>::SessionManager(int scaleDoutPin, int scaleSckPin, uint
 template <typename SessionT>
 void SessionManager<SessionT>::tare()
 {
+    if(measuring_)
+        stopMeasurements();
     Serial.println("Beginning tare");
     scale_.begin(scaleDoutPin_, scaleSckPin_);
     scale_.tare(CONFIG_TARE_AVG_COUNT);
@@ -69,6 +72,8 @@ void SessionManager<SessionT>::begin()
 template <typename SessionT>
 void SessionManager<SessionT>::startMeasurements()
 {
+    if(measuring_ == true)
+        return;
     measuring_ = true;
     lastCallTime_ = 0;
     session_.init(timeClient_.getEpochTime());
@@ -77,6 +82,8 @@ void SessionManager<SessionT>::startMeasurements()
 template <typename SessionT>
 void SessionManager<SessionT>::stopMeasurements()
 {
+    if(measuring_ == false)
+        return;
     session_.finalize();
     measuring_ = false;
 }
@@ -88,8 +95,11 @@ void SessionManager<SessionT>::iteration()
         return;
 
     uint16_t measurement = -1;
-    scale_.measure(measurement);
+    bool measurementDone = false;
+    while(!measurementDone)
+        measurementDone = scale_.measure(measurement);
     bool addPointSuccessful = session_.addPoint(measurement);
+    Serial.printf("Measured: %d\n", measurement);
     if (!addPointSuccessful)
     {
         Serial.println("Maximum time of session reached - stopping");

firmware/lib/session/SimpleMeasurementSession.h

@@ -77,6 +77,10 @@ private:
         if (portablefs::exists(filename.c_str()))
         {
             auto file = portablefs::open(filename.c_str(), "a");
+            file.seek(0, SeekSet);
+            StreamingMsgPackEncoder<portablefs::File> encoder(&file);
+            chunk->sendHeader(encoder, chunk->getStartTime(), 0);
+
             file.seek(0, SeekEnd);
             size_t existingMeasurements = (file.size() - ChunkT::valueOffset()) / sizeof(Measurement_T);
             Serial.printf("Incremental save, existing %d\n", existingMeasurements);