diff --git a/Arduino/SenderTrial2/.vscode/arduino.json b/Arduino/SenderTrial2/.vscode/arduino.json
index 684e9bd..684964e 100644
--- a/Arduino/SenderTrial2/.vscode/arduino.json
+++ b/Arduino/SenderTrial2/.vscode/arduino.json
@@ -3,5 +3,5 @@
     "port": "COM9",
     "sketch": "SenderTrial2.ino",
     "output": "..\\build",
-    "configuration": "PSRAM=disabled,PartitionScheme=default,FlashMode=qio,FlashFreq=80,FlashSize=4M,UploadSpeed=921600,DebugLevel=none"
+    "configuration": "PSRAM=disabled,PartitionScheme=default,FlashMode=qio,FlashFreq=80,FlashSize=4M,UploadSpeed=921600,DebugLevel=warn"
 }
\ No newline at end of file
diff --git a/Arduino/SenderTrial2/Bluetooth.h b/Arduino/SenderTrial2/Bluetooth.h
index 2dc6ea3..283581c 100644
--- a/Arduino/SenderTrial2/Bluetooth.h
+++ b/Arduino/SenderTrial2/Bluetooth.h
@@ -3,10 +3,30 @@
 class CProtocol;
 
 void Bluetooth_Init();
-void Bluetooth_SendFrame(const char* pHdr, const CProtocol& Frame);
+void Bluetooth_SendFrame(const char* pHdr, const CProtocol& Frame, bool lineterm=true);
 void Bluetooth_Check();
 
-extern void Command_Interpret(String line);   // decodes received command lines, implemented in main .ino file!
+extern void Command_Interpret(const char* pLine);   // decodes received command lines, implemented in main .ino file!
+
+struct sRxLine {
+  char Line[64];
+  int  Len;
+  sRxLine() {
+    clear();
+  }
+  bool append(char val) {
+    if(Len < (sizeof(Line) - 1)) {
+      Line[Len++] = val;
+      Line[Len] = 0;
+      return true;
+    }
+    return false;
+  }
+  void clear() {
+    Line[0] = 0;
+    Len = 0;
+  }
+};
 
 
 
diff --git a/Arduino/SenderTrial2/BluetoothESP32.cpp b/Arduino/SenderTrial2/BluetoothESP32.cpp
index bf6bc0e..f0d8bed 100644
--- a/Arduino/SenderTrial2/BluetoothESP32.cpp
+++ b/Arduino/SenderTrial2/BluetoothESP32.cpp
@@ -9,7 +9,7 @@ const int LED = 2;
 
 // ESP32
 
-String BluetoothRxLine;
+sRxLine RxLine;
 
 #ifndef ESP32_USE_BLE_RLJ
 
@@ -25,6 +25,7 @@ BluetoothSerial SerialBT;
 
 void Bluetooth_Init()
 {
+  RxLine.clear();
   pinMode(LED, OUTPUT);
 
   if(!SerialBT.begin("ESPHEATER")) {
@@ -37,18 +38,18 @@ void Bluetooth_Check()
   if(SerialBT.available()) {
     char rxVal = SerialBT.read();
     if(isControl(rxVal)) {    // "End of Line"
-      BluetoothRxLine += '\0';
-      Command_Interpret(BluetoothRxLine);
-      BluetoothRxLine = "";
+      Command_Interpret(RxLine.Line);
+      RxLine.clear();
     }
     else {
-      BluetoothRxLine += rxVal;   // append new char to our Rx buffer
+      RxLine.append(rxVal);
     }
   }
 }
 
-void Bluetooth_SendFrame(const char* pHdr, const CProtocol& Frame)
+void Bluetooth_SendFrame(const char* pHdr, const CProtocol& Frame, bool lineterm)
 {
+  DebugReportFrame(pHdr, Frame, lineterm ? "\r\n" : "   ");
   if(SerialBT.hasClient()) {
 
     if(Frame.verifyCRC()) {
@@ -57,11 +58,11 @@ void Bluetooth_SendFrame(const char* pHdr, const CProtocol& Frame)
       SerialBT.write(Frame.Data, 24);
     }
     else {
-      DebugPort.print("Bluetooth data not sent, CRC error ");
-      DebugPort.println(pHdr);
+      DebugPort.println("Data not sent to Bluetooth, CRC error!");
     }
   }
   else {
+    DebugPort.println("No Bluetooth client");
     digitalWrite(LED, 0);
   }
 }
diff --git a/Arduino/SenderTrial2/BluetoothHC05.cpp b/Arduino/SenderTrial2/BluetoothHC05.cpp
index 1d9d090..6d89092 100644
--- a/Arduino/SenderTrial2/BluetoothHC05.cpp
+++ b/Arduino/SenderTrial2/BluetoothHC05.cpp
@@ -18,7 +18,7 @@ static HardwareSerial& Bluetooth(Serial2); // TODO: make proper ESP32 BT client
 
 bool Bluetooth_ATCommand(const char* cmd);
 
-String BluetoothRxData;
+sRxLine RxLine;
 
 const int BTRates[] = {
   9600, 38400, 115200, 19200, 57600, 2400, 4800
@@ -28,7 +28,8 @@ bool bHC05Available = false;
 
 void Bluetooth_Init()
 {
-
+  RxLine.clear();
+  
   // search for BlueTooth adapter, trying the common baud rates, then less common
   // as the device cannot be guaranteed to power up with the key pin high
   // we are at the mercy of the baud rate stored in the module.
@@ -108,12 +109,11 @@ void Bluetooth_Check()
     if(Bluetooth.available()) {
       char rxVal = Bluetooth.read();
       if(isControl(rxVal)) {    // "End of Line"
-        BluetoothRxData += '\0';
-        Command_Interpret(BluetoothRxData);
-        BluetoothRxData = "";
+        Command_Interpret(RxLine.Line);
+        RxLine.clear();
       }
       else {
-        BluetoothRxData += rxVal;   // append new char to our Rx buffer
+        RxLine.append(rxVal);   // append new char to our Rx buffer
       }
     }
   }
diff --git a/Arduino/SenderTrial2/SenderTrial2.ino b/Arduino/SenderTrial2/SenderTrial2.ino
index b52ccb5..89f29ec 100644
--- a/Arduino/SenderTrial2/SenderTrial2.ino
+++ b/Arduino/SenderTrial2/SenderTrial2.ino
@@ -84,8 +84,6 @@ static UARTClass& BlueWire(Serial1);
 static HardwareSerial& BlueWire(Serial1);  
 #endif
 
-void DebugReportFrame(const char* hdr, const CProtocol& Frame, const char* ftr);
-
 class CommStates {
   public:
     // comms states
@@ -129,7 +127,6 @@ CHeaterStorage NVStorage;   // dummy, for now
 #endif
 CHeaterStorage* pNVStorage = NULL;
 
-
 void setup() 
 {
   // initialize serial port to interact with the "blue wire"
@@ -225,7 +222,7 @@ void loop()
     TxManage.PrepareFrame(DefaultBTCParams, isBTCmaster);  // use our parameters, and mix in NV storage values
     TxManage.Start(timenow);
 #ifdef BLUETOOTH
-    Bluetooth_SendFrame("[BTC]", TxManage.getFrame());    //  BTC => Bluetooth Controller :-)
+    Bluetooth_SendFrame("[BTC]", TxManage.getFrame(), false);    //  BTC => Bluetooth Controller :-)
 #endif
   }
 
@@ -276,18 +273,20 @@ void loop()
     // filled controller frame, report
 #ifdef BLUETOOTH
     // echo received OEM controller frame over Bluetooth, using [OEM] header
-    Bluetooth_SendFrame("[OEM]", OEMControllerFrame);
-#endif
+    Bluetooth_SendFrame("[OEM]", OEMControllerFrame, false);
+#else
     DebugReportFrame("OEM  ", OEMControllerFrame, "  ");
+#endif
     CommState.set(CommStates::HeaterRx1);
   }
     
   else if(CommState.is(CommStates::HeaterReport1) ) {
     // received heater frame (after controller message), report
-    DebugReportFrame("Htr1  ", HeaterFrame1, "\r\n");
 #ifdef BLUETOOTH
     // echo heater reponse data to Bluetooth client
     Bluetooth_SendFrame("[HTR]", HeaterFrame1);
+#else
+    DebugReportFrame("Htr1  ", HeaterFrame1, "\r\n");
 #endif
 
     if(digitalRead(ListenOnlyPin)) {
@@ -303,11 +302,12 @@ void loop()
     
   else if( CommState.is(CommStates::HeaterReport2) ) {
     // received heater frame (after our control message), report
-    DebugReportFrame("Htr2  ", HeaterFrame2, "\r\n");
-//    if(!digitalRead(ListenOnlyPin)) {
 #ifdef BLUETOOTH
-      Bluetooth_SendFrame("[HTR]", HeaterFrame2);    // pin not grounded, suppress duplicate to BT
+    Bluetooth_SendFrame("[HTR]", HeaterFrame2);    // pin not grounded, suppress duplicate to BT
+#else
+    DebugReportFrame("Htr2  ", HeaterFrame2, "\r\n");
 #endif
+//    if(!digitalRead(ListenOnlyPin)) {
 //    }
     CommState.set(CommStates::Idle);
   }
@@ -319,80 +319,86 @@ void DebugReportFrame(const char* hdr, const CProtocol& Frame, const char* ftr)
   DebugPort.print(hdr);                     // header
   for(int i=0; i<24; i++) {
     char str[16];
-    sprintf(str, "%02X ", Frame.Data[i]);  // build 2 dig hex values
+    sprintf(str, " %02X", Frame.Data[i]);  // build 2 dig hex values
     DebugPort.print(str);                   // and print     
   }
   DebugPort.print(ftr);                     // footer
 }
 
-void Command_Interpret(String line)
+void Command_Interpret(const char* pLine)
 {
   unsigned char cVal;
   unsigned short sVal;
+
+  if(strlen(pLine) == 0)
+    return;
   
   #ifdef DEBUG_BTRX
-    DebugPort.println(line);
-    DebugPort.println();
+    DebugPort.println(pLine);
   #endif
 
-  if(line.startsWith("[CMD]") ) {
-    DebugPort.write("BT command Rx'd: ");
+  if(strncmp(pLine, "[CMD]", 5) == 0) {
     // incoming command from BT app!
-    line.remove(0, 5);   // strip away "[CMD]" header
-    if(line.startsWith("ON") ) {
-      DebugPort.write("ON\n");
+    DebugPort.write("  Command decode: ");
+
+    pLine += 5;   // skip past "[CMD]" header
+    if(strncmp(pLine, "ON", 2) == 0) {
       TxManage.queueOnRequest();
+      DebugPort.println("Heater ON");
     }
-    else if(line.startsWith("OFF")) {
-      DebugPort.write("OFF\n");
+    else if(strncmp(pLine, "OFF", 3) == 0) {
       TxManage.queueOffRequest();
+      DebugPort.println("Heater OFF");
     }
-    else if(line.startsWith("Pmin")) {
-      line.remove(0, 4);
-      DebugPort.write("Pmin=");
-      cVal = (line.toFloat() * 10) + 0.5;
-      DebugPort.println(cVal);
+    else if(strncmp(pLine, "Pmin", 4) == 0) {
+      pLine += 4;
+      cVal = (unsigned char)((atof(pLine) * 10.0) + 0.5);
       pNVStorage->setPmin(cVal);
-    }
-    else if(line.startsWith("Pmax")) {
-      line.remove(0, 4);
-      DebugPort.write("Pmax=");
-      cVal = (line.toFloat() * 10) + 0.5;
+      DebugPort.print("Pump min = ");
       DebugPort.println(cVal);
+    }
+    else if(strncmp(pLine, "Pmax", 4) == 0) {
+      pLine += 4;
+      cVal = (unsigned char)((atof(pLine) * 10.0) + 0.5);
       pNVStorage->setPmax(cVal);
-    }
-    else if(line.startsWith("Fmin")) {
-      line.remove(0, 4);
-      DebugPort.print("Fmin=");
-      sVal = line.toInt();
-      DebugPort.println(sVal);
-      pNVStorage->setFmin(sVal);
-    }
-    else if(line.startsWith("Fmax")) {
-      line.remove(0, 4);
-      DebugPort.print("Fmax=");
-      sVal = line.toInt();
-      DebugPort.println(sVal);
-      pNVStorage->setFmax(sVal);
-    }
-    else if(line.startsWith("save")) {
-      line.remove(0, 4);
-      DebugPort.write("save\n");
-      pNVStorage->save();
-    }
-    else if(line.startsWith("degC")) {
-      line.remove(0, 4);
-      DebugPort.write("degC=");
-      cVal = line.toInt();
+      DebugPort.print("Pump max = ");
       DebugPort.println(cVal);
-      pNVStorage->setTemperature(cVal);
     }
-    else if(line.startsWith("Mode")) {
-      line.remove(0, 4);
-      DebugPort.write("Mode=");
+    else if(strncmp(pLine, "Fmin", 4) == 0) {
+      pLine += 4;
+      sVal = atoi(pLine);
+      pNVStorage->setFmin(sVal);
+      DebugPort.print("Fan min = ");
+      DebugPort.println(sVal);
+    }
+    else if(strncmp(pLine, "Fmax", 4) == 0) {
+      pLine += 4;
+      sVal = atoi(pLine);
+      pNVStorage->setFmax(sVal);
+      DebugPort.print("Fan max = ");
+      DebugPort.println(int(sVal));
+    }
+    else if(strncmp(pLine, "save", 4) == 0) {
+      pNVStorage->save();
+      DebugPort.println("NV save");
+    }
+    else if(strncmp(pLine, "degC", 4) == 0) {
+      pLine += 4;
+      cVal = atoi(pLine);
+      pNVStorage->setTemperature(cVal);
+      DebugPort.print("degC = ");
+      DebugPort.println(cVal);
+    }
+    else if(strncmp(pLine, "Mode", 4) == 0) {
+      pLine += 4;
       cVal = !pNVStorage->getThermostatMode();
       pNVStorage->setThermostatMode(cVal);
-      DebugPort.println(cVal);
+      DebugPort.print("Mode = ");
+      DebugPort.println(cVal ? "Thermostat" : "Fixed Hz");
+    }
+    else {
+      DebugPort.print(pLine);
+      DebugPort.println(" ????");
     }
 
   }
diff --git a/Arduino/SenderTrial2/TxManage.cpp b/Arduino/SenderTrial2/TxManage.cpp
index e3c95ef..702f2bf 100644
--- a/Arduino/SenderTrial2/TxManage.cpp
+++ b/Arduino/SenderTrial2/TxManage.cpp
@@ -100,7 +100,7 @@ CTxManage::CheckTx(unsigned long timenow)
       // begin serial transmission
       m_bTxPending = false;
       m_BlueWireSerial.write(m_TxFrame.Data, 24);  // write native binary values
-      DebugReportFrame("BTC  ", m_TxFrame, "  ");  // report frame to debug port
+//      DebugReportFrame("BTC  ", m_TxFrame, "  ");  // report frame to debug port
     }
     if(diff > (m_nStartDelay + m_nFrameTime)) {
       // conclude Tx gating
diff --git a/Arduino/SenderTrial2/debugport.h b/Arduino/SenderTrial2/debugport.h
index 2def60c..94ade9c 100644
--- a/Arduino/SenderTrial2/debugport.h
+++ b/Arduino/SenderTrial2/debugport.h
@@ -1,8 +1,12 @@
 
+class CProtocol;
 
 #if defined(__arm__)
 // Typically Arduino Due
 static UARTClass& DebugPort(Serial);
 #else
 static HardwareSerial& DebugPort(Serial);   // reference Serial as DebugPort
-#endif
\ No newline at end of file
+#endif
+
+void DebugReportFrame(const char* hdr, const CProtocol& Frame, const char* ftr);
+