Deadband helper & tests (#1267)

* deadband

* header

* comment

firmware/util/math/deadband.h

@@ -0,0 +1,29 @@
+/**
+ * @file    deadband.h
+ *
+ * @date April 6, 2020
+ * @author Matthew Kennedy, (c) 2020
+ */
+
+#pragma once
+
+#include "efilib.h"
+
+template <int TDeadband>
+class Deadband {
+public:
+	bool gt(float lhs, float rhs) {
+		// If we're within the deadband, be "sticky" with the previous value
+		float absError = absF(lhs - rhs);
+
+		// If there's enough error, actually compare values
+		if (absError > TDeadband) {
+			m_lastState = lhs > rhs;
+		}
+
+		return m_lastState;
+	}
+
+private:
+	bool m_lastState =false;
+};

unit_tests/tests/test_deadband.cpp

@@ -0,0 +1,38 @@
+#pragma once
+#include <gtest/gtest.h>
+#include "deadband.h"
+
+TEST(Deadband, OutsideDeadband) {
+	Deadband<5> d;
+
+	EXPECT_TRUE(d.gt(100, 0));
+	EXPECT_FALSE(d.gt(0, 100));
+}
+
+TEST(Deadband, InsideDeadband) {
+	Deadband<5> d;
+
+	// stick the state to true
+	EXPECT_TRUE(d.gt(10, 0));
+
+	// Make sure it stays there while inside the deadband
+	EXPECT_TRUE(d.gt(0, 0));
+	EXPECT_TRUE(d.gt(0, 1));
+	EXPECT_TRUE(d.gt(0, 2));
+	EXPECT_TRUE(d.gt(0, 3));
+	EXPECT_TRUE(d.gt(0, 4));
+	EXPECT_TRUE(d.gt(0, 4.99));
+
+	// Flip the state - it should now stick false
+	EXPECT_FALSE(d.gt(0, 5.01));
+
+	// Make sure it stays there while inside the deadband
+	EXPECT_FALSE(d.gt(0, 4.99));
+	EXPECT_FALSE(d.gt(0, 1));
+	EXPECT_FALSE(d.gt(0, -1));
+	EXPECT_FALSE(d.gt(0, -1));
+	EXPECT_FALSE(d.gt(0, -4.99));
+
+	// Now it should flip back
+	EXPECT_TRUE(d.gt(0, -5.01));
+}

unit_tests/tests/tests.mk

@@ -36,6 +36,7 @@ TESTS_SRC_CPP = \
 	tests/test_tacho.cpp \
 	tests/test_gpiochip.cpp \
 	tests/test_multispark.cpp \
+	tests/test_deadband.cpp \
 	tests/sensor/basic_sensor.cpp \
 	tests/sensor/func_sensor.cpp \
 	tests/sensor/function_pointer_sensor.cpp \