add Chapter18

Chapter18/accelerometer_interface.cpp

@@ -0,0 +1,53 @@
+#include <cstdio>
+#include <cstdint>
+
+class accelerometer {
+public:
+    struct data{
+        float x;
+        float y;
+        float z;
+    };
+    enum class sampling_rate {
+        c_20_hz,
+        c_50_hz,
+        c_100_hz,
+    };
+    virtual void set_sampling_rate(sampling_rate) = 0;
+    virtual data get_data() = 0;
+};
+
+class adxl_345 : public accelerometer {
+public:
+    void set_sampling_rate(sampling_rate) override {
+        printf("adxl_345: setting sampling rate\r\n");
+    }
+    data get_data() override {
+        return data{0.02f, 0.981f, 0.03f};
+    }
+};
+
+class tap_detection_algo {
+public:
+    tap_detection_algo(accelerometer &accel) : 
+        accel_(accel) {
+            accel_.set_sampling_rate(accelerometer::sampling_rate::c_100_hz);
+    }
+    bool run () {
+        auto accel_data = accel_.get_data();
+        printf("algo: x = %.2f, y = %.2f, z = %.2f\r\n", 
+               accel_data.x, accel_data.y, accel_data.z);
+        // process data
+        return false;
+    }
+private:
+    accelerometer &accel_;
+};
+
+int main() {
+    adxl_345 accel;
+    tap_detection_algo algo(accel);
+    algo.run();
+
+    return 0;
+}