arch.example.tex

   1 \subsection{Framework}
   2 Systems built with support for \gls{mTask} are often following the same design
   3 pattern. First the devices are created --- with or without the interaction of
   4 the user --- and they are then connected. When all devices are registered, the
   5 \gls{mTask}-\glspl{Task} can be sent and \gls{iTasks}-\glspl{Task} can be
   6 started to monitor the output. When everything is finished, the devices are
   7 removed and the system is shut down.
   8
   9 \begin{lstlisting}[language=Clean,label={lst:framework},
  10         caption={\gls{mTask} framework for building applications}]
  11 w :: Task ()
  12 w =         makeDevice "dev1" (...) >>= connectDevice
  13         >>= \dev1->makeDevice "dev2" (...) >>= connectDevice
  14         >>= \dev2->...
  15         ...
  16         >>* [OnAction (Action "Shutdown") $ always
  17                 $   deleteDevice dev1 >>| deleteDevice dev2
  18                 >>| ...
  19                 >>| shutDown 0
  20         ]
  21 \end{lstlisting}
  22
  23 \subsection{Thermostat}
  24 The thermostat is a classic example program for showing interactions between
  25 peripherals. The following program shows a system containing two devices. The
  26 first device --- the sensor -- contains a temperature sensor that measures the
  27 room temperature. The second device --- the actor --- contains a heater,
  28 connected to the digital pin \CI{D5}. Moreover, this device contains a led to
  29 indicate whether the heater is on. The following code shows an implementation
  30 for this. The code fully uses the framework. Note that a little bit of type
  31 twiddling is required to fully us the result from the \gls{SDS}. This approach
  32 is still type safe due to the type safety of \CI{Dynamic}s.
  33
  34 \begin{lstlisting}[caption={Thermostat example}]
  35 thermos :: Task ()
  36 thermos =           makeDevice "nodeM" nodeMCU >>= connectDevice
  37         >>= \nod->      makeDevice "stm32" stm32   >>= connectDevice
  38         >>= \stm->      sendTaskToDevice "sensing" sensing (nod, OnInterval 1000)
  39         >>= \(st, [t])->sendTaskToDevice "acting" acting (stm, OnInterval 1000)
  40                         (\(BCValue s)->set (BCValue $ dynInt (dynamic s) > 0) (shareShare nod a))
  41         >>| treturn ()
  42 where
  43         dynInt :: Dynamic -> Int
  44         dynInt (a :: Int) = a
  45
  46         sensing = sds \x=0 In {main=
  47                         x =. analogRead A0 :. pub x
  48                 }
  49         acting = sds \cool=False In {main=
  50                         IF cool (ledOn LED1) (ledOff LED1) :.
  51                         digitalWrite D5 cool
  52                 }
  53         nodeMCU = TCP
  54 \end{lstlisting}
  55
  56 \subsection[Lifting mTasks to iTasks-Tasks]%
  57         {Lifting \gls{mTask}-\glspl{Task} to \gls{iTasks}-\glspl{Task}}
  58 If the user does not want to know where and when a \gls{mTask} is actually
  59 executed and is just interested in the results it can lift the \gls{mTask} to
  60 an \gls{iTasks}-\gls{Task}. The function is called with a name, \gls{mTask},
  61 device and interval specification and it will return a \gls{Task} that finishes
  62 if and only if the \gls{mTask} has returned.
  63
  64 \begin{lstlisting}[caption={Lifting \gls{mTask}-\glspl{Task} to \gls{iTasks}}]
  65 liftmTask :: String (Main (ByteCode () Stmt)) (MTaskDevice, MTaskInterval) -> Task [MTaskShare]
  66 liftmTask wta mTask c=:(dev, _)= sendTaskToDevice wta mTask c
  67         >>= \(t, shs)->wait "Waiting for mTask to return" (taskRemoved t) (deviceShare dev)
  68         >>| viewInformation "Done!" [] ()
  69         >>| treturn shs
  70 where
  71         taskRemoved t d = isNothing $ find (\t1->t1.ident==t.ident) d.deviceTasks
  72 \end{lstlisting}
  73
  74 The factorial example can then be lifted to a real \gls{iTasks}-\gls{mTask}
  75 with the following code:
  76 \begin{lstlisting}[caption={Lifting the factorial \gls{Task} to \gls{iTasks}}]
  77 factorial :: MTaskDevice -> Task BCValue
  78 factorial dev = enterInformation "Factorial of ?" []
  79         >>= \fac->liftmTask "fact" (fact fac) (dev, OnInterval 100)
  80         @         fromJust o find (\x->x.humanName == "result")
  81         @         \s->s.MTaskShare.value
  82 where
  83         fact i = sds \y=i
  84                 In namedsds \x=(1 Named "result")
  85                 In {main = IF (y <=. lit 1)
  86                         ( pub x :. retrn                  )
  87                         ( x =. x *. y :.  y =. y -. lit 1 )}
  88 \end{lstlisting}
  89
  90 \subsection{Heartbeat \& Oxygen Saturation Sensor}
  91 As an example, the addition of a new sensor will be demonstrated. The heartbeat
  92 and oxygen saturation sensor is a \textsc{PCB} the size of a fingernail with a
  93 red \gls{LED} and a light sensor on it. Moreover, it contains an \textsc{I2C}
  94 chip to communicate. The company producing the chip provides the programmer
  95 with example code for \gls{Arduino} and \textsc{mbed}. So suppose %TODO
  96 Adding peripheral is supposedly simple.