Merge branch 'samd21_dev' into dev

Author: runger1101001

src/drivers/hardware_specific/generic_mcu.cpp

@@ -14,6 +14,8 @@
 
 #elif defined(_SAMD21_)  // samd21 for the moment, samd51 in progress...
 
+#elif defined(_SAMD51_)  // samd21 for the moment, samd51 in progress...
+
 #else
 
 // function setting the high pwm frequency to the supplied pins