\subsection{Framework}
-Systems built with support for \gls{mTask} are often following the same design
+Systems built with support for \gls{mTask} often follow the same design
pattern. First the devices are created --- with or without the interaction of
the user --- and they are then connected. When all devices are registered, the
\gls{mTask}-\glspl{Task} can be sent and \gls{iTasks}-\glspl{Task} can be
peripherals. The following program shows a system containing two devices. The
first device --- the sensor --- contains a temperature sensor that measures the
room temperature. The second device --- the actor --- contains a heater,
-connected to the digital pin \CI{D5}. Moreover, this device contains a led to
-indicate whether the heater is on. The following code shows an implementation
-for this. The code fully uses the framework. Note that a little bit of type
-twiddling is required to fully us the result from the \gls{SDS}. This approach
-is still type safe due to the type safety of \CI{Dynamic}s.
-
-\begin{lstlisting}[caption={Thermostat example}]
+connected to the digital pin \CI{D5}. Moreover, this device contains an
+\gls{LED} to indicate whether the heater is on. The following code shows an
+implementation for this. The code makes use of all the aspects of the
+framework. Note that a little bit of type twiddling is required to fully use
+the result from the \gls{SDS}. This approach is still type safe due to the type
+safety of \CI{Dynamic}s.
+
+\begin{lstlisting}[language=Clean,caption={Thermostat example}]
thermos :: Task ()
thermos = makeDevice "nodeM" nodeMCU >>= connectDevice
>>= \nod-> makeDevice "stm32" stm32 >>= connectDevice
>>= \stm-> sendTaskToDevice "sensing" sensing (nod, OnInterval 1000)
>>= \(st, [t])->sendTaskToDevice "acting" acting (stm, OnInterval 1000)
(\(BCValue s)->set (BCValue $ dynInt (dynamic s) > 0) (shareShare nod a))
- >>| treturn ()
+ >>* [OnAction (Action "Shutdown") $ always $ deleteDevice nod >>| deleteDevice stm >>| shutDown 0]
where
dynInt :: Dynamic -> Int
dynInt (a :: Int) = a
IF cool (ledOn LED1) (ledOff LED1) :.
digitalWrite D5 cool
}
- nodeMCU = TCP
+ nodeMCU = makeDevice "NodeMCU"
+ (TCPDevice {host="192.168.0.12", port=8888})
+ stm32 = makeDevice "Stm32"
+ (SerialDevice {devicePath="/dev/ttyUSB0", baudrate=B9600, ...}
\end{lstlisting}
\subsection[Lifting mTasks to iTasks-Tasks]%
{Lifting \gls{mTask}-\glspl{Task} to \gls{iTasks}-\glspl{Task}}
-If the user does not want to know where and when a \gls{mTask} is actually
-executed and is just interested in the results it can lift the \gls{mTask} to
+If the user does not want to know where and when an \gls{mTask} is actually
+executed and is just interested in the results, it can lift the \gls{mTask} to
an \gls{iTasks}-\gls{Task}. The function is called with a name, \gls{mTask},
device and interval specification and it will return a \gls{Task} that finishes
if and only if the \gls{mTask} has returned.
-\begin{lstlisting}[caption={Lifting \gls{mTask}-\glspl{Task} to \gls{iTasks}}]
+\begin{lstlisting}[language=Clean,caption={Lifting \gls{mTask}-\glspl{Task} to \gls{iTasks}}]
liftmTask :: String (Main (ByteCode () Stmt)) (MTaskDevice, MTaskInterval) -> Task [MTaskShare]
liftmTask wta mTask c=:(dev, _)= sendTaskToDevice wta mTask c
>>= \(t, shs)->wait "Waiting for mTask to return" (taskRemoved t) (deviceShare dev)
\end{lstlisting}
The factorial function example from Chapter~\ref{chp:mtaskcont} can then be
-lifted to a real \gls{iTasks}-\gls{mTask} with the following code:
-\begin{lstlisting}[caption={Lifting the factorial \gls{Task} to \gls{iTasks}}]
+lifted to a real \gls{iTasks}-\gls{Task} with the following code:
+\begin{lstlisting}[language=Clean,caption={Lifting the factorial \gls{Task} to \gls{iTasks}}]
factorial :: MTaskDevice -> Task BCValue
factorial dev = enterInformation "Factorial of ?" []
>>= \fac->liftmTask "fact" (fact fac) (dev, OnInterval 100)
and oxygen saturation sensor add-on is a \textsc{PCB} the size of a fingernail
with a red \gls{LED} and a light sensor on it. Moreover, it contains an
\textsc{I2C} chip to communicate. The company producing the chip provides the
-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.
+programmer with example code for \gls{Arduino} and \gls{mbed}. The sensor
+emits red light and measures the intensity of the light returned. 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 \gls{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
+oxygen saturation and the validity of the two. The real value and the validity
+are combined in an \gls{ADT} and functions are added for both of them in the
+new \CI{hb} class. The values are combined in such a way that they fit in a 16
+bit integer with the last bit representing the validity of the reading. 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
+\begin{lstlisting}[language=Clean,%
+ caption={The \texttt{hb} class and class implementations}]
+:: Heartbeat = HB Int Bool
+:: SP02 = SP02 Int Bool
+
+instance toByteCode Heartbeat
+ where toByteCode (HB i b) = "h" +++ (to16bit $ (i << 1) bitand (if b 1 0))
+instance toByteCode SP02 where ...
+
+instance fromByteCode Heartbeat
+ where fromByteCode s = let i = fromByteCode s //The Int from bytecode
+ in HB (i >> 1) (i bitand 1 > 0)
+instance fromByteCode SP02 where ...
-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}
implementation. Dedicated bytecode instructions have been added to support the
functionality.
-\begin{lstlisting}[caption={The \texttt{hb} bytecode instance}]
+\begin{lstlisting}[language=Clean,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.
+When adding a peripheral, the devices not having the peripheral do not need to
+have their code recompiled. New instructions always get a higher bytecode
+number if added correctly. The peripheral byte in the device specification by
+default shows a negative flag for every peripheral. Only the peripherals added
+will be flagged positive.
-\begin{lstlisting}[caption={Adding the device interface}]
+\begin{lstlisting}[language=Clean,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
...
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}
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:
+so that the interface functions for it can access it. This is listed in
+Listing~\ref{lst:hbding}. If interrupts were implemented, the \glspl{Task}
+using the heartbeat sensor could be executed on interrupt. The heartbeat thread
+can fire an interrupt everytime it calculated a new heartbeat.
-\begin{lstlisting}[language=C,caption={}]
+\begin{lstlisting}[label={lst:hbding},language=C,%
+ caption={Heartbeat code in the client}]
Serial pc;
Thread thread;
thread.start(heartbeat_thread);
}
\end{lstlisting}
+
+\subsubsection{Example}
+The following code shows a complete example of a \gls{Task} controlling an
+\emph{STM} microcontroller containing a heartbeat sensor. The web application
+belonging to the server shows the heartbeat value and starts an alert
+\gls{Task} when it exceeds the value given or is no longer valid.
+This example also shows how named \gls{SDS} are handled.
+
+\begin{lstlisting}[language=Clean,caption={Heartbeat example}]
+hbwatch :: (Task a) Int -> Task ()
+hbwatch alert lim
+ = makeDevice "stm32" stm32
+ >>= connectDevice
+ >>= \stm ->sendTaskToDevice "monitor" monitor (stm, OnInterval 200)
+ >>= \(t, sh)->mon (fromJust $ find (\x->x.name == "hb") sh)
+ >>* [OnAction (Action "Shutdown") $ always $ deleteDevice stm >>| shutDown 0]
+where
+ mon :: (Shared BCValue) -> Task ()
+ mon b = whileUnchanged (mapRead dynHB b)
+ \hb=:(HB i valid)->if (not valid || i > lim)
+ alert (viewInformation "HB Okay" [] hb)
+
+ dynHB :: Dynamic -> HeartBeat
+ dynHB (a :: HeartBeat) = a
+
+ monitor = namedsds \hb=(0 Named hb) In
+ {main= hb = getHB :. pub hb }
+\end{lstlisting}
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