mtaskext.taskstrat.tex

   1 The current \gls{mTask} engine for devices does not support \glspl{Task} in the
   2 sense that the \gls{C}-view does. \Glspl{Task} used with the \gls{C}-view are a
   3 main program that executes code and launches \glspl{Task}. It was also possible
   4 to just have a main program. The current \gls{mTask}-system only supports main
   5 programs which are the \glspl{Task} in their entirety. However, this results in
   6 a problem. \glspl{Task} can not call other \glspl{Task} nor themselves.
   7 Therefore, execution strategies have been added. Sending a \gls{Task} always
   8 goes together with choosing a scheduling strategy. This strategy can be one of
   9 the following three strategies:
  10
  11 \begin{itemize}
  12         \item\CI{OneShot}
  13
  14                 The \CI{OneShot} strategy consists of executing the \gls{Task} only
  15                 once. In \gls{IoT} applications, often the status of a peripheral or
  16                 system has to be queried only once on the request of the user. For
  17                 example in a thermostat, the temperature is logged every 30 minutes.
  18                 However, the user might want to know the temperature at that exact
  19                 moment, and then they can just send a \CI{OneShot} \gls{Task} probing
  20                 the temperature. After execution, the \gls{Task} will be removed from
  21                 the memory of the client.
  22         \item\CI{OnInterval Int}
  23
  24                 \CI{OnInterval} is a execution strategy that executes the \gls{Task}
  25                 in the given number of milliseconds. This strategy is very useful for
  26                 logging measurements on an interval. Moreover, the strategy can be
  27                 (ab)used to simulate recursion. \glspl{SDS} store global % chktex 36
  28                 information and is persistent. The \CI{retrn} instruction --- as will
  29                 be shown in Section~\ref{ssec:control} --- can then be used to
  30                 terminate. Therefore, \glspl{Task} can be crafted that recursively call
  31                 themselves using a \gls{SDS} to simulate arguments.
  32         \item\CI{OnInterrupt Int}
  33
  34                 Finally, a scheduling method is available that executes a \gls{Task}
  35                 when a given interrupt is received. This method can be useful to launch
  36                 a \gls{Task} on the press on hardware events such as the press of a
  37                 button. Unfortunately, due to time constraints and focus, this
  38                 functionality is only built in the protocol, none of the current client
  39                 implementations support this.
  40 \end{itemize}