Testing external clock detection and auto-switch

Simplified audio spectrum computation and transfer
ACARS RX in debug mode
Disabled ABI warnings
Updated binary

firmware/chibios/os/kernel/src/chschd.c

@@ -148,6 +148,7 @@ static void wakeup(void *p) {
 #if CH_USE_SEMAPHORES
   case THD_STATE_WTSEM:
     chSemFastSignalI((Semaphore *)tp->p_u.wtobjp);
+    __attribute__ ((fallthrough));
     /* Falls into, intentional. */
 #endif
 #if CH_USE_QUEUES