more subsections for design chapter

src/design_methodology_and_implementation.tex

@@ -19,7 +19,13 @@
 
 % SPI - image
 
-\subsubsection{Analogue to Digital Conversion}
+\subsubsection{Methods for accessing external devices}
+
+% Polling
+
+% Interrupts
+
+\subsubsection{Low Power Mode}
 
 \subsection{System Design}