ST ISM330DLC IMU driver

src/lib/mathlib/math/filter/LowPassFilter2p.hpp

@@ -66,7 +66,7 @@ public:
 	// Reset the filter state to this value
 	float reset(float sample);
 
-private:
+protected:
 
 	float _cutoff_freq{0.0f};
 

src/lib/mathlib/math/filter/LowPassFilter2pArray.hpp

@@ -0,0 +1,85 @@
+/****************************************************************************
+ *
+ *   Copyright (C) 2019 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/// @file	LowPassFilter2pArray.hpp
+/// @brief	A class to implement a second order low pass filter
+
+#pragma once
+
+#include "LowPassFilter2p.hpp"
+
+namespace math
+{
+
+class LowPassFilter2pArray : public LowPassFilter2p
+{
+public:
+
+	LowPassFilter2pArray(float sample_freq, float cutoff_freq) : LowPassFilter2p(sample_freq, cutoff_freq)
+	{
+	}
+
+	/**
+	 * Add a new raw value to the filter
+	 *
+	 * @return retrieve the filtered result
+	 */
+	inline float apply(const int16_t samples[], uint8_t num_samples)
+	{
+		float output = 0.0f;
+
+		for (int n = 0; n < num_samples; n++) {
+			// do the filtering
+			float delay_element_0 = samples[n] - _delay_element_1 * _a1 - _delay_element_2 * _a2;
+
+			if (n == num_samples - 1) {
+				output = delay_element_0 * _b0 + _delay_element_1 * _b1 + _delay_element_2 * _b2;
+			}
+
+			_delay_element_2 = _delay_element_1;
+			_delay_element_1 = delay_element_0;
+		}
+
+		// don't allow bad values to propagate via the filter
+		if (!PX4_ISFINITE(output)) {
+			reset(samples[num_samples - 1]);
+			output = samples[num_samples - 1];
+		}
+
+		// return the value. Should be no need to check limits
+		return output;
+	}
+
+};
+
+} // namespace math