Try to handle syshalt.

cfg/chconf.h

@@ -810,6 +810,7 @@
  */
 #define CH_CFG_SYSTEM_HALT_HOOK(reason) {                                   \
   /* System halt code here.*/                                               \
+  while (*reason) { USART_DR_DR = *reason; reason ++; } \
 }
 
 /**