add Chapter07

Chapter07/error_handling/hal/uart/inc/uart.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <cstdint>
+
+#include <span>
+
+namespace hal
+{
+class uart
+{
+  public:
+    virtual void init(std::uint32_t baudrate) = 0;
+    virtual void write_array(const char * ptr, std::size_t len) = 0;
+
+    virtual void write(std::span<const char> data)
+    {
+      write_array(data.data(), data.size());
+    }
+};
+}; // namespace hal