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diff --git a/firmware/os/algos/calibration/sample_rate_estimator/sample_rate_estimator.h b/firmware/os/algos/calibration/sample_rate_estimator/sample_rate_estimator.h
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+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * [Sample Rate Estimator]
+ * This module periodically estimates the mean sampling rate of a uniformly
+ * sampled signal. Note, this estimator uses a floating point accumulator for
+ * the timing intervals. This trades-off some accumulation of finite precision
+ * error to enhance the range of estimated sampling rates and prevent overflow
+ * when an equivalent 32bit integer accumulator is used. In typical use cases
+ * (sample rates: 5Hz - 2kHz, num_intervals_to_collect 10 - 100), the sample
+ * rate accuracy is typically much better than 0.1Hz.
+ *
+ * FUNCTIONALITY:
+ * sampleRateEstimatorInit -- Initializes the estimator. Sets the number of time
+ *   intervals require to compute the sample rate mean, and the upper limit for
+ *   the acceptable time interval.
+ *
+ * new_sampling_rate_estimate_ready -- Check this boolean flag if polling for
+ *   new estimates is desired.
+ *
+ * sampleRateEstimatorGetHz -- Returns the latest sample rate estimate and
+ *   resets the polling flag.
+ *
+ * sampleRateEstimatorUpdate -- Processes new timestamp data and computes new
+ *   sample rate estimates.
+ */
+
+#ifndef LOCATION_LBS_CONTEXTHUB_NANOAPPS_CALIBRATION_SAMPLE_RATE_ESTIMATOR_SAMPLE_RATE_ESTIMATOR_H_
+#define LOCATION_LBS_CONTEXTHUB_NANOAPPS_CALIBRATION_SAMPLE_RATE_ESTIMATOR_SAMPLE_RATE_ESTIMATOR_H_
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Designates the value used to indicate an invalid sample rate estimate.
+#define SAMPLE_RATE_ESTIMATOR_INVALID_SAMPLE_RATE_HZ (-1.0f)
+
+// Sample rate estimator data structure.
+struct SampleRateEstimator {
+  // Used to compute sample intervals to estimate the sampling rate.
+  uint64_t last_timestamp_nanos;
+
+  // Accumulator used for computing the mean sampling interval.
+  float interval_accumulator_nanos;
+
+  // The upper limit on the acceptance of valid time intervals (in nanoseconds).
+  // Larger time deltas result in a reset of the interval accumulator.
+  float max_interval_nanos;
+
+  // The most recent mean sampling rate estimate.
+  float mean_sampling_rate_estimate_hz;
+
+  /*
+   * The targeted number of time intervals required for a new sample rate mean
+   * calculation.
+   *
+   * NOTE: Assuming that the time interval noise is independent and identically
+   * distributed and drawn from a zero-mean normal distribution with variance
+   * 'Sigma^2'. The expected noise reduction is related to the choice of
+   * 'num_intervals_to_collect' as:
+   *
+   *   Output RMS Noise = Sigma / sqrt(num_intervals_to_collect).
+   *
+   * Example, a value of 100 for a 100Hz signal would provide updates once every
+   * second and provide a 90% reduction (i.e., [1 - 1/sqrt(100)] * 100%) in time
+   * interval noise.
+   */
+  size_t num_intervals_to_collect;
+
+  // The number of time intervals currently collected.
+  size_t num_intervals_collected;
+
+  // Polling flag used to signal that a new estimate is ready. This flag is
+  // reset when 'sampleRateEstimatorGetHz' is called.
+  bool new_sampling_rate_estimate_ready;
+};
+
+// Initializes the sample rate estimator, sets the number of time intervals
+// for the mean sample rate calculation, and defines the tolerable gap in timing
+// data (in seconds).
+void sampleRateEstimatorInit(struct SampleRateEstimator* sample_rate_estimator,
+                             size_t num_intervals_to_collect,
+                             float max_interval_sec);
+
+// Rather than using a function to poll for new sample rate estimates, which
+// would incur an additional function call, simply check
+// 'new_sampling_rate_estimate_ready' directly.
+
+// Returns the most recent sampling rate estimate, and resets the
+// 'new_sampling_rate_estimate_ready' polling flag. Note, if polling is not
+// used, one may access the sample rate estimate directly from the struct and
+// avoid this function call.
+float sampleRateEstimatorGetHz(
+    struct SampleRateEstimator* sample_rate_estimator);
+
+// Takes in a new timestamp and updates the sampling rate estimator.
+void sampleRateEstimatorUpdate(
+    struct SampleRateEstimator* sample_rate_estimator,
+    uint64_t timestamp_nanos);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // LOCATION_LBS_CONTEXTHUB_NANOAPPS_CALIBRATION_SAMPLE_RATE_ESTIMATOR_SAMPLE_RATE_ESTIMATOR_H_