diff --git a/Config.h b/Config.h
index a6d60a3..2027c33 100644
--- a/Config.h
+++ b/Config.h
@@ -58,7 +58,7 @@
 // Frequencies such as 10.0 Mhz (48000 * 208.333) or 20 Mhz (48000 * 416.666) are not suitable.
 //
 // For 12 MHz
-// #define EXTERNAL_OSC 12000000
+#define EXTERNAL_OSC 12000000
 // For 12.288 MHz
 // #define EXTERNAL_OSC 12288000
 // For 14.4 MHz
@@ -66,10 +66,10 @@
 // For 19.2 MHz
 // #define EXTERNAL_OSC 19200000
 
-// Use a higher baudrate for host communication. Required for FM network !
-// #define SERIAL_SPEED 115200 //suitable for most older boards (Arduino, Due STM32F1_POG etc). External FM will NOT work with this !
-// #define SERIAL_SPEED 230400 // Only works on newer board M4, M7, Teensy. External FM might work with this
-#define SERIAL_SPEED 460800 // Only works on newer board M4, M7, Teensy. External FM should work with this
+// Select a baud rate for host communication. The faster speeds are needed for external FM to work.
+// #define SERIAL_SPEED 115200 // Suitable for most older boards (Arduino Due, STM32F1_POG, etc). External FM will NOT work with this!
+// #define SERIAL_SPEED 230400 // Only works on newer boards like fast M4, M7, Teensy 3.x. External FM might work with this
+#define SERIAL_SPEED 460800	// Only works on newer boards like fast M4, M7, Teensy 3.x. External FM should work with this
 
 // Allow the use of the COS line to lockout the modem
 // #define USE_COS_AS_LOCKOUT
@@ -129,5 +129,11 @@
 // Use the D-Star and YSF LEDs for FM
 #define USE_ALTERNATE_FM_LEDS
 
+#if defined(STM32F1_POG)
+// Slower boards need to run their serial at 115200 baud
+#undef SERIAL_SPEED
+#define SERIAL_SPEED 115200
+#endif
+
 #endif
 
diff --git a/IO.cpp b/IO.cpp
index 7ad2067..e12110e 100644
--- a/IO.cpp
+++ b/IO.cpp
@@ -746,6 +746,7 @@ void CIO::setMode(MMDVM_STATE state)
     case STATE_M17:    setM17Int(false);    break;
     case STATE_POCSAG: setPOCSAGInt(false); break;
     case STATE_FM:     setFMInt(false);     break;
+    default: break;
   }
 
   switch (state) {
@@ -757,6 +758,7 @@ void CIO::setMode(MMDVM_STATE state)
     case STATE_M17:    setM17Int(true);    break;
     case STATE_POCSAG: setPOCSAGInt(true); break;
     case STATE_FM:     setFMInt(true);     break;
+    default: break;
   }
 #endif
 
diff --git a/M17RX.cpp b/M17RX.cpp
index 1e0dc92..6e10e35 100644
--- a/M17RX.cpp
+++ b/M17RX.cpp
@@ -214,6 +214,8 @@ void CM17RX::processData(q15_t sample)
       case M17RXS_PACKET:
         DEBUG4("M17RX: packet sync found pos/centre/threshold", m_syncPtr, m_centreVal, m_thresholdVal);
         break;
+      default:
+        break;  
     }
 
     uint8_t frame[M17_FRAME_LENGTH_BYTES + 3U];
@@ -249,6 +251,8 @@ void CM17RX::processData(q15_t sample)
         case M17RXS_PACKET:
           writeRSSIPacket(frame);
           break;
+        default:
+          break;  
       }
 
       m_maxCorr   = 0;
diff --git a/SerialPort.cpp b/SerialPort.cpp
index efeb4ca..3a51798 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -374,22 +374,41 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
   bool rxInvert        = (data[0U] & 0x01U) == 0x01U;
   bool txInvert        = (data[0U] & 0x02U) == 0x02U;
   bool pttInvert       = (data[0U] & 0x04U) == 0x04U;
+#if defined(MODE_YSF)
   bool ysfLoDev        = (data[0U] & 0x08U) == 0x08U;
+#endif
   bool useCOSAsLockout = (data[0U] & 0x20U) == 0x20U;
   bool simplex         = (data[0U] & 0x80U) == 0x80U;
 
   m_debug = (data[0U] & 0x10U) == 0x10U;
 
+#if defined(MODE_DSTAR)
   bool dstarEnable  = (data[1U] & 0x01U) == 0x01U;
+#endif
+#if defined(MODE_DMR)
   bool dmrEnable    = (data[1U] & 0x02U) == 0x02U;
+#endif
+#if defined(MODE_YSF)
   bool ysfEnable    = (data[1U] & 0x04U) == 0x04U;
+#endif
+#if defined(MODE_P25)
   bool p25Enable    = (data[1U] & 0x08U) == 0x08U;
+#endif
+#if defined(MODE_NXDN)
   bool nxdnEnable   = (data[1U] & 0x10U) == 0x10U;
+#endif
+#if defined(MODE_FM)
   bool fmEnable     = (data[1U] & 0x20U) == 0x20U;
+#endif
+#if defined(MODE_M17)
   bool m17Enable    = (data[1U] & 0x40U) == 0x40U;
-
+#endif
+#if defined(MODE_POCSAG)
   bool pocsagEnable = (data[2U] & 0x01U) == 0x01U;
+#endif
+#if defined(MODE_AX25)
   bool ax25Enable   = (data[2U] & 0x02U) == 0x02U;
+#endif
 
   uint8_t txDelay = data[3U];
   if (txDelay > 50U)
@@ -480,17 +499,28 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
   uint8_t fmTXLevel     = data[16U];
   uint8_t ax25TXLevel   = data[17U];
 
+#if defined(MODE_YSF)
   uint8_t ysfTXHang     = data[20U];
+#endif
+#if defined(MODE_P25)
   uint8_t p25TXHang     = data[21U];
+#endif
+#if defined(MODE_NXDN)
   uint8_t nxdnTXHang    = data[22U];
+#endif
+#if defined(MODE_M17)
   uint8_t m17TXHang     = data[23U];
+#endif
 
+#if defined(MODE_DMR)
   uint8_t colorCode = data[26U];
   if (colorCode > 15U)
     return 4U;
 
   uint8_t dmrDelay = data[27U];
+#endif
 
+#if defined(MODE_AX25)
   int8_t ax25RXTwist    = int8_t(data[28U]) - 128;
   if (ax25RXTwist < -4 || ax25RXTwist > 10)
     return 4U;
@@ -498,6 +528,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
   uint8_t ax25TXDelay   = data[29U];
   uint8_t ax25SlotTime  = data[30U];
   uint8_t ax25PPersist  = data[31U];
+#endif
 
   setMode(modemState);
 
@@ -939,7 +970,7 @@ void CSerialPort::process()
     }
     writeSerialData(buffer, serialAvail - m_lastSerialAvail);
     m_lastSerialAvailCount = 0U;
-  } else if (serialAvail > 0U && serialAvail == m_lastSerialAvail) {
+  } else if (serialAvail > 0 && serialAvail == m_lastSerialAvail) {
     m_lastSerialAvailCount++;
   } else {
     m_lastSerialAvail      = serialAvail;
diff --git a/Version.h b/Version.h
index 0c90f87..9841303 100644
--- a/Version.h
+++ b/Version.h
@@ -19,7 +19,7 @@
 #if !defined(VERSION_H)
 #define  VERSION_H
 
-#define VERSION "20210617"
+#define VERSION "20210719"
 
 #endif