elaborate hb

diff --git a/arch.example.tex b/arch.example.tex
index 4627aab..a65ffd5 100644 (file)
--- a/arch.example.tex
+++ b/arch.example.tex
@@ -96,5 +96,113 @@ programmer with example code for \gls{Arduino} and \textsc{mbed}. The sensor
 emits red light and measures the returning light intensity. The microcontroller
 hosting the device has to keep track of four seconds of samples to determine
 the heartbeat. In the \gls{mTask}-system, an abstraction is made. The current
-implementation runs on \textsc{mbed} supported devices. 
-%TODO Adding peripheral is supposedly simple.
+implementation runs on \textsc{mbed} supported devices.
+
+\subsubsection{\gls{mTask} Classes}
+First, a class has to be devised to store the functionality of the sensor. The
+heartbeat sensor updates four values continuously, namely the heartbeat, the
+validity of the reading, the oxygen saturation and the validity of it. For
+every value a function is added to the new \CI{hb} class. Moreover, the
+introduced datatype housing the values should implement the \CI{mTaskType}
+classes. The definition is as follows:
+
+\begin{lstlisting}[caption={The \texttt{hb} class}]
+:: Heartbeat = HB Int
+:: SP02      = SP02 Int
+
+instance toByteCode Heartbeat, SP02
+instance fromByteCode Heartbeat, SP02
+derive class iTask Heartbeat, SP02
+
+class hb v where
+       getHb     :: (v Heartbeat Expr)
+       validHb   :: (v Bool Expr)
+       getSp02   :: (v SP02 Expr)
+       validSp02 :: (v Bool Expr)
+\end{lstlisting}
+
+\subsubsection{Bytecode Implementation}
+The class is available now, and the implementation can be created. The
+implementation is trivial since the functionality is limited to retrieving
+single values and no assignment is possible. The following code shows the
+implementation. Dedicated bytecode instructions have been added to support the
+functionality.
+
+\begin{lstlisting}[caption={The \texttt{hb} bytecode instance}]
+:: BC
+       = BCNop
+       | ...
+       | BCGetHB
+       | BCValidHB
+       | BCGetSP02
+       | BCValidSP02
+       | ...
+
+instance hb ByteCode where
+       getHb = tell` [BCGetHB]
+       validHb = tell` [BCValidHB]
+       getSp02 = tell` [BCGetSP02]
+       validSp02 = tell` [BCValidSP02]
+\end{lstlisting}
+
+\subsubsection{Device Interface}
+The bytecode instructions are added but still the functionality needs to be
+added to the device interface to be implemented by clients. The following
+addition to \CI{interface.h} and the interpreter shows the added instructions.
+
+\begin{lstlisting}[caption={Adding the device interface}]
+// interface.h
+...
+#if HAVEHB == 1
+uint16_t get_hb();
+bool     valid_hb();
+uint16_t get_spo2();
+bool     valid_spo2();
+#endif
+...
+
+// interpret.c
+       while(pc < plen){
+               switch(program[pc++]){
+               ...
+#if HAVEHB == 1
+               case BCGETHB:
+                       stack[sp++] = get_hb();
+                       break;
+               case BCVALIDHB:
+                       stack[sp++] = valid_hb();
+                       break;
+               case BCGETSP02:
+                       stack[sp++] = get_spo2();
+                       break;
+               case BCVALIDSP02:
+                       stack[sp++] = valid_spo2();
+                       break;
+#endif
+               ...
+\end{lstlisting}
+
+\subsubsection{Client Software}
+The device client software always executes the \CI{real\_setup} in which the
+client software can setup the connection and peripherals. In the case of the
+heartbeat peripheral it starts a thread running the calculations. The thread
+started in the setup will set the global heartbeat and oxygen level variables
+so that the interface functions for it can access it. The code is then as
+follows:
+
+\begin{lstlisting}[language=C,caption={}]
+Serial pc;
+Thread thread;
+
+void heartbeat_thread(void) {
+       // Constant heartbeat calculations
+}
+
+void real_setup(void) {
+       pc.baud(19200);
+       thread.start(heartbeat_thread);
+}
+\end{lstlisting}
+
+\subsubsection{Example Program}
+% todo