Provide error message when trying to compile this library for the M4 core. (#22)

Author: aentinger

src/Arduino_AdvancedAnalog.h

@@ -24,6 +24,10 @@
  * INCLUDE
  **************************************************************************************/
 
+#ifdef ARDUINO_PORTENTA_H7_M4
+# error "This library on works on the M7 core of any STM32H747 based board (Portenta H7, Giga, X8)."
+#endif
+
 #include "AdvancedADC.h"
 #include "AdvancedDAC.h"