Added I2C support for raspi & first rework of debugging

include/sta/bus/spi/spi.hpp

@@ -0,0 +1,47 @@
+/**
+ * @file
+ * @brief SPI bus software interface.
+ */
+#ifndef STA_CORE_SPI_SPI_HPP
+#define STA_CORE_SPI_SPI_HPP
+
+#include <sta/bus/interface.hpp>
+#include <sta/bus/spi/settings.hpp>
+#include <sta/mutex.hpp>
+
+#include <cstddef>
+#include <cstdint>
+
+
+namespace sta
+{
+    /**
+     * @brief Interface class for %SPI hardware.
+     *
+     * Represents a single %SPI bus that can be shared by multiple devices.
+     *
+     * @ingroup sta_core_spi
+     */
+    class SPI : public Interface
+    {
+    public:
+        /**
+         * @param settings  %SPI bus settings
+         * @param mutex     Mutex object for managing shared access. Pass nullptr for no access control
+         */
+        SPI(const SPISettings & settings, Mutex * mutex = nullptr);
+
+        /**
+         * @brief Get %SPI interface settings.
+         *
+         * @return %SPI settings
+         */
+        const SPISettings & settings();
+
+    private:
+        SPISettings settings_;  /**< %SPI settings */
+    };
+} // namespace sta
+
+
+#endif // STA_CORE_SPI_SPI_HPP