[ardrone2] Parrot GPS show sattelite information.

closes #474

sw/airborne/boards/ardrone/at_com.h

@@ -178,7 +178,7 @@ typedef struct _navdata_gps_t {
   uint8_t       unk_2[16];
   struct{
     uint8_t     sat;
-    uint8_t     unk;
+    uint8_t     cn0;
   }channels[12];
   int32_t       gps_plugged;            /*!< When the gps is plugged */
   uint8_t       unk_3[108];

sw/airborne/subsystems/gps/gps_ardrone2.c

@@ -36,6 +36,7 @@ void gps_impl_init( void ) {
 }
 
 void gps_ardrone2_parse(navdata_gps_t *navdata_gps) {
+  int i;
   // Set the lla double struct from the navdata
   struct LlaCoor_d gps_lla_d;
   gps_lla_d.lat = RadOfDeg(navdata_gps->lat);
@@ -51,6 +52,12 @@ void gps_ardrone2_parse(navdata_gps_t *navdata_gps) {
   LLA_BFP_OF_REAL(gps.lla_pos, gps_lla_d);
 
   // TODO: parse other stuff
+  gps.nb_channels = GPS_NB_CHANNELS;
+
+  for(i = 0; i < GPS_NB_CHANNELS; i++) {
+    gps.svinfos[i].svid = navdata_gps->channels[i].sat;
+    gps.svinfos[i].cno = navdata_gps->channels[i].cn0;
+  }
 
   // Check if we have a fix TODO: check if 2D or 3D fix?
   if (navdata_gps->gps_state == 1)

sw/airborne/subsystems/gps/gps_ardrone2.h

@@ -30,7 +30,7 @@
 
 #include "boards/ardrone/at_com.h"
 
-//#define GPS_NB_CHANNELS 12 // TODO: Get channels out of packet
+#define GPS_NB_CHANNELS 12
 extern bool_t gps_ardrone2_available;
 
 /*