Integrate asynchronous GPS IMU fusion

soc/software/gps_system/header/imu/imu_calibration.h

@@ -0,0 +1,33 @@
+#ifndef IMU_CALIBRATION_H
+#define IMU_CALIBRATION_H
+
+#include <stdbool.h>
+
+#include "imu/imu_sample.h"
+
+/*
+ * Sensor-independent calibration in the IMU body frame.
+ *
+ * corrected = transform * (measured - bias - temperature_coefficient * dT)
+ *
+ * The transform can contain scale, cross-axis and mounting-axis corrections.
+ * Temperature correction is deliberately opt-in; collecting temperature does
+ * not change measurements unless temperature_compensation_enabled is true.
+ */
+typedef struct {
+	double accel_bias_mps2[3];
+	double gyro_bias_rps[3];
+	double accel_transform[3][3];
+	double gyro_transform[3][3];
+	double reference_temperature_c;
+	double accel_temperature_coefficient_mps2_per_c[3];
+	double gyro_temperature_coefficient_rps_per_c[3];
+	bool temperature_compensation_enabled;
+} imu_calibration_t;
+
+void imu_calibration_default(imu_calibration_t* calibration);
+bool imu_calibration_is_valid(const imu_calibration_t* calibration);
+bool imu_calibration_apply(const imu_calibration_t* calibration,
+	                       imu_sample_t* measurement);
+
+#endif

soc/software/gps_system/header/imu/imu_sample.h

@@ -0,0 +1,18 @@
+#ifndef IMU_SAMPLE_H
+#define IMU_SAMPLE_H
+
+#include <stdint.h>
+
+/*
+ * Sensor-independent, calibrated inertial sample in SI units.  Drivers and
+ * IMU management publish this type without depending on GPS or ESKF headers.
+ */
+typedef struct {
+	uint64_t timestamp_ticks;
+	double accel_mps2[3];
+	double gyro_rps[3];
+	double temperature_c;
+	uint32_t sequence;
+} imu_sample_t;
+
+#endif

soc/software/gps_system/header/imu/imu_sensor.h

@@ -0,0 +1,68 @@
+#ifndef IMU_SENSOR_H
+#define IMU_SENSOR_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "imu/imu_calibration.h"
+#include "imu/imu_sample.h"
+
+typedef enum {
+	IMU_SENSOR_NONE = 0,
+	IMU_SENSOR_TDK_ICM42688,
+	IMU_SENSOR_ST_LSM6DSOX,
+	IMU_SENSOR_BACKEND_COUNT
+} imu_sensor_backend_t;
+
+typedef struct {
+	/* Zero selects the active backend's safe default.  A non-zero target may
+	 * be quantized to a nearby hardware ODR; diagnostics reports both values. */
+	uint32_t odr_hz;
+	unsigned int accel_full_scale_g;
+	unsigned int gyro_full_scale_dps;
+	/* Auto-detected devices must never share board-specific calibration. */
+	imu_calibration_t calibration_by_backend[IMU_SENSOR_BACKEND_COUNT];
+} imu_sensor_config_t;
+
+typedef struct {
+	uint64_t irq_count;
+	uint64_t sample_count;
+	uint64_t invalid_sample_count;
+	uint64_t spurious_irq_count;
+	uint64_t queue_overflow_count;
+	uint64_t estimated_missed_sample_count;
+	uint64_t last_timestamp_ticks;
+	uint32_t requested_odr_hz;
+	uint32_t configured_odr_hz;
+	uint8_t who_am_i;
+	imu_sensor_backend_t backend;
+	bool initialized;
+	bool running;
+	bool foreground_polling;
+} imu_sensor_diagnostics_t;
+
+void imu_sensor_default_config(imu_sensor_config_t* config);
+
+/* Probe the compiled backend(s), select one, validate the requested ODR/range
+ * and prepare calibration.  This does not enable data-ready interrupts. */
+bool imu_sensor_init(const imu_sensor_config_t* config);
+
+/* Configure streaming and enable BSP_PMOD_IRQ.  The application must attach
+ * imu_sensor_irq_handler to the active machine-interrupt router first. */
+bool imu_sensor_start(void);
+void imu_sensor_stop(void);
+
+/* PLIC/ISR half: read and timestamp one raw sample, then enqueue it. */
+void imu_sensor_irq_handler(void);
+
+/* Foreground half. Safe no-op for the current interrupt-driven backends. */
+void imu_sensor_service(void);
+bool imu_sensor_requires_foreground_service(void);
+
+/* Pop the oldest sample, convert to SI/common axes and apply the selected
+ * backend's calibration.  No averaging or motion decision occurs here. */
+bool imu_sensor_take_measurement(imu_sample_t* measurement_out);
+void imu_sensor_get_diagnostics(imu_sensor_diagnostics_t* diagnostics_out);
+imu_sensor_backend_t imu_sensor_active_backend(void);
+const char* imu_sensor_backend_name(imu_sensor_backend_t backend);
+#endif