Allow targets to use 1 or two buttons.

src/main/main.c

@@ -196,13 +196,17 @@ void init(void)
 #endif
 
 #if defined(BUTTONS)
+#ifdef BUTTON_A_PIN
     IO_t buttonAPin = IOGetByTag(IO_TAG(BUTTON_A_PIN));
     IOInit(buttonAPin, OWNER_SYSTEM, 0);
     IOConfigGPIO(buttonAPin, IOCFG_IPU);
+#endif
 
+#ifdef BUTTON_B_PIN
     IO_t buttonBPin = IOGetByTag(IO_TAG(BUTTON_B_PIN));
     IOInit(buttonBPin, OWNER_SYSTEM, 0);
     IOConfigGPIO(buttonBPin, IOCFG_IPU);
+#endif
 
     // Check status of bind plug and exit if not active
     delayMicroseconds(10);  // allow configuration to settle