added data structures

added audio support
added rfid support
added spi support

data/DoubleBuffer.h

@@ -0,0 +1,70 @@
+#ifndef DOUBLEBUFFER_H
+#define DOUBLEBUFFER_H
+
+template <typename Scalar, int size> class DoubleBuffer {
+
+private:
+
+	Scalar data[size*2];
+	Scalar* ptr1;
+	Scalar* ptr2;
+
+	volatile uint32_t head;
+	volatile bool _needsFlush;
+
+public:
+
+	void init() {
+		ptr1 = &data[0];
+		ptr2 = &data[size];
+		head = 0;
+		_needsFlush = false;
+	}
+
+	/** add new values to buffer A. swaps A and B if A is full */
+	void add(const Scalar value) {
+
+		ptr1[head] = value; // ptr1
+		++head;
+
+		if (head >= size) {
+			head = 0;
+			swap();
+			_needsFlush = true;
+		}
+
+	}
+
+	/** get data from buffer B */
+	const Scalar* getData() const {
+		return ptr2;
+	}
+
+	/** true if the buffer is currently empty */
+	bool isEmpty() const {
+		return head == 0;
+	}
+
+	bool needsFlush() const {
+		return _needsFlush;
+	}
+
+	void markFlushed() {
+		_needsFlush = false;
+	}
+
+	uint32_t getSize() const {
+		return size;
+	}
+
+private:
+
+	void swap() {
+		Scalar* tmp = ptr1;
+		ptr1 = ptr2;
+		ptr2 = tmp;
+	}
+
+};
+
+#endif // DOUBLEBUFFER_H