bind inverter rf-quality (from heuristic) to display radio RSSI bars

src/plugins/Display/Display.h

@@ -87,6 +87,7 @@ class Display {
 
         uint8_t nrprod = 0;
         uint8_t nrsleep = 0;
+        int8_t  minQAllInv = 4;
 
         Inverter<> *iv;
         record_t<> *rec;
@@ -97,6 +98,15 @@ class Display {
             if (iv == NULL)
                 continue;
 
+            int8_t maxQInv = -6;
+            for(uint8_t ch = 0; ch < RF_MAX_CHANNEL_ID; ch++) {
+                int8_t q = iv->txRfQuality[ch];
+                if (q > maxQInv)
+                    maxQInv = q;
+            }
+            if (maxQInv < minQAllInv)
+                minQAllInv = maxQInv;
+
             rec = iv->getRecordStruct(RealTimeRunData_Debug);
 
             if (iv->isProducing())
@@ -123,7 +133,7 @@ class Display {
         mDisplayData.RadioSymbol = mHmRadio->isChipConnected();
         mDisplayData.WifiSymbol = (WiFi.status() == WL_CONNECTED);
         mDisplayData.MQTTSymbol = mApp->getMqttIsConnected();
-        mDisplayData.RadioRSSI = (0 < mDisplayData.nrProducing) ? 0 : SCHAR_MIN;  // Workaround as NRF24 has no RSSI. Could be approximated by transmisson error heuristic in the future
+        mDisplayData.RadioRSSI = (0 < mDisplayData.nrProducing) ? ivQuality2RadioRSSI(minQAllInv) : SCHAR_MIN; // Workaround as NRF24 has no RSSI. Approximation by quality levels from heuristic function
         mDisplayData.WifiRSSI = (WiFi.status() == WL_CONNECTED) ? WiFi.RSSI() : SCHAR_MIN;
         mDisplayData.ipAddress = WiFi.localIP();
         time_t utc= mApp->getTimestamp();
@@ -148,6 +158,26 @@ class Display {
 #endif
     }
 
+    // approximate RSSI in dB by invQuality levels from heuristic function (very unscientific but better than nothing :-) )
+    int8_t ivQuality2RadioRSSI(int8_t invQuality) {
+        int8_t pseudoRSSIdB;
+        switch(invQuality) {
+            case  4: pseudoRSSIdB = -55; break;
+            case  3:
+            case  2:
+            case  1: pseudoRSSIdB = -65; break;
+            case  0:
+            case -1:
+            case -2: pseudoRSSIdB = -75; break;
+            case -3:
+            case -4:
+            case -5: pseudoRSSIdB = -85; break;
+            case -6:
+            default:  pseudoRSSIdB = -95; break;
+        }
+        return (pseudoRSSIdB);
+    }
+
     // private member variables
     IApp *mApp;
     DisplayData mDisplayData;