increase first start interrupt and default device in downlink.h

sw/airborne/arch/lpc21/mcu_periph/sys_time_arch.c

@@ -120,7 +120,7 @@ void sys_time_arch_init( void ) {
   T0EMR = 0;
 
   /* set first sys tick interrupt    */
-  T0MR0 = sys_time.resolution_cpu_ticks;
+  T0MR0 = 4*sys_time.resolution_cpu_ticks;
 
   /* enable timer 0                  */
   T0TCR = TCR_ENABLE;

sw/airborne/subsystems/datalink/downlink.h

@@ -63,6 +63,12 @@
 #define DefaultChannel DOWNLINK_TRANSPORT
 #endif
 
+// FIXME are DOWNLINK_AP|FBW_DEVICE distinction really necessary ?
+// by default use AP_DEVICE if nothing is set ?
+#ifndef DOWNLINK_DEVICE
+#define DOWNLINK_DEVICE DOWNLINK_AP_DEVICE
+#endif
+
 #ifndef DefaultDevice
 #define DefaultDevice DOWNLINK_DEVICE
 #endif