Index: webserver/example/EnergyMeters/Source/EnergyMeters/SolarCountUART.c
===================================================================
--- webserver/example/EnergyMeters/Source/EnergyMeters/SolarCountUART.c (revision 44)
+++ webserver/example/EnergyMeters/Source/EnergyMeters/SolarCountUART.c (revision 56)
@@ -8,8 +8,26 @@
 #include "task.h"
 #include "serial.h"
+#include "MetersIncludes.h"
+
+
+static void advanceHistoryArray(void);
 
 #define solarSTACK_SIZE		configMINIMAL_STACK_SIZE+200
 
 #define SOLAR_READ_DELAY         500
+
+/* after what inactivity time (ms) do we determine the solar FSM as stuck? */
+#define SOLAR_FSM_STUCK_TIMEOUT  2000
+
+/* means "unknown value", converted to "U" on rrdtool script side */
+#define SOLAR_FSM_INVALID_VALUE  0x4000 /* 16384 */
+
+
+
+int SolarHistory[SOLAR_WATT_HISTORYSIZE][3]; /* three watt values: P1, P2, P3 */
+int historyRemainTime = SOLAR_WATT_HISTORY_STEPSIZE; /* how many ticks have we left until the next history entry must be written? */
+
+
+
 
 // Pin I/O LED Control Maskbit
@@ -106,4 +124,8 @@
 portTickType xLastSolarStateChangeTime;
 
+ /* time when the elements of the history array were last moved on one step */
+portTickType xLastSolarHistoryAdvance;
+
+
 
 int solarReadErrors = 0;
@@ -141,5 +163,7 @@
 void initSolarFSM(void)
 {
+  int i;
   xLastSolarStateChangeTime = xTaskGetTickCount();
+  xLastSolarHistoryAdvance = xTaskGetTickCount();
   xLastReadTime = xTaskGetTickCount();
   solarState = SOL_NO_INIT;
@@ -147,4 +171,18 @@
   rxBuf3NextFreeRxPos = 0;
   currentChannel = 0;
+
+  /* set data to invalid value */
+  chanWatt[0] = SOLAR_FSM_INVALID_VALUE;
+  chanWatt[1] = SOLAR_FSM_INVALID_VALUE;
+  chanWatt[2] = SOLAR_FSM_INVALID_VALUE;
+
+  /* invalidate history */
+  for (i = 0; i < SOLAR_WATT_HISTORYSIZE; i++)
+  {
+            SolarHistory[i][0] = SOLAR_FSM_INVALID_VALUE;
+            SolarHistory[i][1] = SOLAR_FSM_INVALID_VALUE;
+            SolarHistory[i][2] = SOLAR_FSM_INVALID_VALUE;
+  }
+
 } /* initSolarFSM */
 
@@ -326,5 +364,5 @@
 
   /* did the SolarFSM get stuck during reading? */
-  if (xTaskGetTickCount() > xLastSolarStateChangeTime + 5000)
+  if (xTaskGetTickCount() > xLastSolarStateChangeTime + SOLAR_FSM_STUCK_TIMEOUT)
   {
     /* something has gone wrong (possible Rx Timeout). restart, state SOL_NO_INIT */
@@ -332,4 +370,20 @@
     initSolarFSM();
     solarReadErrors++;
+  }
+  else if (xTaskGetTickCount() < xLastSolarStateChangeTime)
+  {
+    /* overflow of timer, just recover. delay will be wrong. */
+    xLastSolarStateChangeTime = xTaskGetTickCount();
+  }
+
+
+  if (xTaskGetTickCount() > (xLastSolarHistoryAdvance + SOLAR_WATT_HISTORY_STEPSIZE))
+  {
+    advanceHistoryArray();
+  }
+  else if (xTaskGetTickCount() < xLastSolarHistoryAdvance)
+  {
+    /* overflow of timer, just recover. delay will be wrong. */
+    xLastSolarHistoryAdvance = xTaskGetTickCount();
   }
 
@@ -454,6 +508,8 @@
         if ((currentChannel >= 0) && (currentChannel < 6))
         {
+          portENTER_CRITICAL();
           chanVolt[currentChannel] = rxUART3[11];
           chanWatt[currentChannel] = (int)(rxUART3[7]) | (((int)(rxUART3[8])) << 8) /* index 7: LSB, index 8: MSB */;
+          portEXIT_CRITICAL();
         } /* if */
 
@@ -495,4 +551,30 @@
 
 
+/*
+ * Check if we have to save the current data to the next history array set, and do it
+ * if necessary.
+ *
+ */
+static void advanceHistoryArray(void)
+{
+  int i;
+
+  /* advance entries by 1. we do not care about data locking here. */
+  for (i = 0; i < (SOLAR_WATT_HISTORYSIZE-1); i++)
+  {
+    portENTER_CRITICAL();
+    SolarHistory[i+1][0] = SolarHistory[i][0];
+    SolarHistory[i+1][1] = SolarHistory[i][1];
+    SolarHistory[i+1][2] = SolarHistory[i][2];
+    portEXIT_CRITICAL();
+  } /* for */
+  /* get the most recent values to index 0 */
+  portENTER_CRITICAL();
+  SolarHistory[0][0] = chanWatt[0];
+  SolarHistory[0][1] = chanWatt[1];
+  SolarHistory[0][2] = chanWatt[2];
+  portEXIT_CRITICAL();
+
+} /* advanceHistoryArray() */
 
 
Index: webserver/example/EnergyMeters/Source/EnergyMeters/MetersIncludes.h
===================================================================
--- webserver/example/EnergyMeters/Source/EnergyMeters/MetersIncludes.h (revision 50)
+++ webserver/example/EnergyMeters/Source/EnergyMeters/MetersIncludes.h (revision 56)
@@ -28,2 +28,11 @@
 meterItem meterItems[NUMBER_OF_METERS]; /* the data for all the meters */
 
+/* the history spans (SOLAR_WATT_HISTORYSIZE * SOLAR_WATT_HISTORY_STEPSIZE) / 1000 seconds */
+
+/* how many old values of the three wattages do we keep? */
+#define SOLAR_WATT_HISTORYSIZE        10
+/* how far are the values apart? in milliseconds */
+#define SOLAR_WATT_HISTORY_STEPSIZE   3000
+extern int SolarHistory[SOLAR_WATT_HISTORYSIZE][3]; /* three watt values: P1, P2, P3 */
+extern int historyRemainTime; /* how many ticks have we left until the next history entry must be written? */
+