Integrate asynchronous GPS IMU fusion

soc/software/gps_system/header/gps_system.h

@@ -0,0 +1,28 @@
+#ifndef GPS_SYSTEM_APP_H
+#define GPS_SYSTEM_APP_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "fusion/fusion_measurement.h"
+#include "fusion/navigation_fusion.h"
+#include "gps/NavEquations.h"
+#include "imu/imu_sample.h"
+
+/* Application-owned messages and lifecycle state at the GPS/IMU/fusion
+ * boundary.  Solver, driver and ESKF private state remain in their modules. */
+typedef struct {
+	gps_nav_solution_t gps_solution;
+	fusion_gps_measurement_t gps_for_fusion;
+	imu_sample_t imu_sample;
+	navigation_fusion_output_t fused_solution;
+	uint64_t gps_measurement_ticks;
+	uint64_t last_status_tick;
+	bool gps_epoch_ready;
+	bool fusion_enabled;
+	bool imu_initialized;
+	bool fusion_initialized;
+	bool imu_running;
+} gps_system_state_t;
+
+#endif