Tweak for Ram usage (#129)

* Add KNX_NO_DEFAULT_UART to avoid default uart assignation for ArduinoPlatforms and derivatives, with associated defines (HWSERIAL_NONE for stm32) to recover RAM from unused RX/TX buffers
Remove ArduinoPlatform(HardwareSerial* knxSerial) constructor, seems not useable by KnxFacade

* Restore ArduinoPlatform::ArduinoPlatform(HardwareSerial* knxSerial) constructor

* revert xxxPlatform(HardwareSerial* s) constructors

src/arduino_platform.cpp

@@ -6,7 +6,13 @@
 #include <SPI.h>
 #endif
 
+#ifndef KNX_NO_PRINT
 Stream* ArduinoPlatform::SerialDebug = &Serial;
+#endif
+
+ArduinoPlatform::ArduinoPlatform() : _knxSerial(nullptr)
+{
+}
 
 ArduinoPlatform::ArduinoPlatform(HardwareSerial* knxSerial) : _knxSerial(knxSerial)
 {
@@ -29,6 +35,7 @@ void ArduinoPlatform::fatalError()
 
 void ArduinoPlatform::knxUart( HardwareSerial* serial )
 {
+    if (_knxSerial)
         closeUart();
     _knxSerial = serial;
     setupUart();

src/arduino_platform.h

@@ -2,11 +2,10 @@
 
 #include "Arduino.h"
 
-extern Stream& _serialDBG;
-
 class ArduinoPlatform : public Platform
 {
   public:
+    ArduinoPlatform();
     ArduinoPlatform(HardwareSerial* knxSerial);
 
     // basic stuff
@@ -29,7 +28,9 @@ class ArduinoPlatform : public Platform
     void closeSpi() override;
     int readWriteSpi (uint8_t *data, size_t len) override;
 #endif
+#ifndef KNX_NO_PRINT
     static Stream* SerialDebug;
+#endif
 
   protected:
     HardwareSerial* _knxSerial;

src/esp32_platform.cpp

@@ -6,7 +6,10 @@
 
 #include "knx/bits.h"
 
-Esp32Platform::Esp32Platform() : ArduinoPlatform(&Serial1)
+Esp32Platform::Esp32Platform()
+#ifndef KNX_NO_DEFAULT_UART
+    : ArduinoPlatform(&Serial1)
+#endif
 {
 }
 

src/esp_platform.cpp

@@ -7,7 +7,10 @@
 
 #include "knx/bits.h"
 
-EspPlatform::EspPlatform() : ArduinoPlatform(&Serial)
+EspPlatform::EspPlatform()
+#ifndef KNX_NO_DEFAULT_UART
+    : ArduinoPlatform(&Serial)
+#endif
 {
 }
 

src/samd_platform.cpp

@@ -6,7 +6,10 @@
 #include <Arduino.h>
 #include <FlashAsEEPROM.h>
 
-SamdPlatform::SamdPlatform() : ArduinoPlatform(&Serial1)
+SamdPlatform::SamdPlatform()
+#ifndef KNX_NO_DEFAULT_UART
+    : ArduinoPlatform(&Serial1)
+#endif
 {
 }
 

src/stm32_platform.cpp

@@ -4,7 +4,10 @@
 #include <stm32_eeprom.h>
 #include "knx/bits.h"
 
-Stm32Platform::Stm32Platform() : ArduinoPlatform(&Serial2)
+Stm32Platform::Stm32Platform()
+#ifndef KNX_NO_DEFAULT_UART
+    : ArduinoPlatform(&Serial2)
+#endif
 {
 }