Option for not using external oscillator

firmware/inc/hw_config.h

@@ -121,6 +121,7 @@
 /**
  * XOSC
  */
+//define USE_XOSC
 #define XOSC_FREQUENCY		16369000
 #define XOSC_GCLK1_DIVIDE	4
 

firmware/src/xosc.c

@@ -48,6 +48,7 @@ measurement_result_t _callback;
  * connects it to GLCK1.
  */
 void xosc_init(void) {
+#ifdef USE_XOSC
   system_clock_source_xosc_set_config(SYSTEM_CLOCK_EXTERNAL_CLOCK,
                                       SYSTEM_XOSC_STARTUP_1,
                                       true,
@@ -57,10 +58,15 @@ void xosc_init(void) {
   system_clock_source_enable(SYSTEM_CLOCK_SOURCE_XOSC);
 
   while (!system_clock_source_is_ready(SYSTEM_CLOCK_SOURCE_XOSC));
+#endif
 
   /* Configure GCLK1 to XOSC */
   system_gclk_gen_set_config(GCLK_GENERATOR_1,
+#ifdef USE_XOSC
         		     GCLK_SOURCE_XOSC, /* Source 		*/
+#else
+                             GCLK_SOURCE_OSC8M, /* Source 		*/
+#endif
         		     false,		/* High When Disabled	*/
         		     XOSC_GCLK1_DIVIDE,/* Division Factor	*/
         		     false,		/* Run in standby	*/