results.arch.tex

   1 \section{Devices}
   2 The client code for the devices is compiled from one codebase. For a device to
   3 be eligible for \glspl{mTask}, it must be able to compile the shared codebase
   4 and implement (part of) the device specific interface. The shared codebase only
   5 uses standard \gls{C} and no special libraries or tricks are used. Therefore
   6 the code is compilable for almost any device or system. Note that it is not
   7 needed to implement a full interface. The full interface --- excluding the
   8 device specific settings --- is listed in Appendix~\ref{app:device-interface}.
   9 The interface works in a similar fashion as the \gls{EDSL}. Devices do not have
  10 to implement all functionality, this is analogous to the fact that views do not
  11 have to implement all type classes in the \gls{EDSL}.  When the device connects
  12 for the first time with a server the specifications of what is implemented is
  13 communicated.
  14
  15 At the time of writing the following device families are supported and can run
  16 the device software.
  17 \begin{itemize}
  18         \item \texttt{POSIX} compatible systems
  19
  20                 This includes systems running \emph{Linux} and \emph{MacOS}.
  21         \item \texttt{STM32} family microcontrollers supported by \texttt{ChibiOS}.
  22
  23                 This is tested in particular on the \texttt{STM32f7x} series \gls{ARM}
  24                 development board.
  25         \item Microcontrollers programmable by the \gls{Arduino} \gls{IDE}.\\
  26
  27                 This does not only include \gls{Arduino} compatible boards but also
  28                 other boards capable of running \gls{Arduino} code. The code
  29                 has been found working on the \texttt{ESP8266} powered \emph{NodeMCU}.
  30                 It is tested on devices as small as the regular \gls{Arduino}
  31                 \emph{UNO} board that only boasts a meager \emph{2K} of \emph{RAM}.
  32 \end{itemize}
  33
  34 \section{Specification}
  35 Devices are stored in a record type and all devices in the system are stored in
  36 a \gls{SDS} containing all devices. From the macro settings in the interface
  37 file a profile is created for the device that describes the specification. When
  38 a connection between the server and a client is established the server will
  39 send a request for specification. The client will serialize his specification
  40 and send it to the server so that the server knows what the client is capable
  41 of. The exact specification is listed in Listing~\ref{lst:devicespec}
  42
  43 \begin{lstlisting}[label={lst:devicespec},
  44         caption={Device specification for \glspl{mTask}}]
  45 :: MTaskDeviceSpec =
  46         {haveLed     :: Bool
  47         ,haveAio     :: Bool
  48         ,haveDio     :: Bool
  49         ,bytesMemory :: Int
  50         }
  51 \end{lstlisting}
  52
  53 \section{Device Storage}
  54 All devices available in the system are stored in a big \gls{SDS} that contains
  55 a list of \CI{MTaskDevice}s. The exact specification is listed in
  56 Listing~\ref{lst:mtaskdevice} with the accompanying classes and types.
  57
  58 The \CI{deviceResource} component of the record must implement the
  59 \CI{MTaskDuplex} interface that provides a function that launches a task used
  60 for synchronizing the channels.  The \CI{deviceTask} stores the \gls{Task}-id
  61 for this \gls{Task} when active so that it can be checked upon. This top-level
  62 task has the duty to report set the \CI{deviceError} field whenever an error
  63 occurs. All communication goes via these channels. If the system wants to send
  64 a message to the device it just puts it in the channels. Messages sent from the
  65 client to the server are also placed in there. In the case of the \gls{TCP}
  66 device type the \gls{Task} is just a simple wrapper around the existing
  67 \CI{tcpconnect} function in \gls{iTasks}. In case of the serial device type it
  68 uses the newly developed serial port library of \gls{Clean}\footnote{\url{%
  69 https://gitlab.science.ru.nl/mlubbers/CleanSerial}}.
  70
  71 Besides all the communication information the record also keeps track of the
  72 \glspl{Task} currently on the device and the according \glspl{SDS}. Finally it
  73 stores the specification of the device that is received when connecting.
  74 All of this is listed in Listing~\ref{lst:mtaskdevice}. The definitions of the
  75 message format are explained in the following section.
  76
  77 \begin{lstlisting}[caption={Device type},label={lst:mtaskdevice}]
  78 deviceStore :: Shared [MTaskDevice]
  79
  80 :: Channels :== ([MTaskMSGRecv], [MTaskMSGSend], Bool)
  81 :: MTaskResource
  82         = TCPDevice TCPSettings
  83         | SerialDevice TTYSettings
  84 :: MTaskDevice =
  85                 { deviceTask :: Maybe TaskId
  86                 , deviceError :: Maybe String
  87                 , deviceChannels :: String
  88                 , deviceName :: String
  89                 , deviceTasks :: [MTaskTask]
  90                 , deviceData :: MTaskResource
  91                 , deviceSpec :: Maybe MTaskDeviceSpec
  92                 , deviceShares :: [MTaskShare]
  93         }
  94
  95 channels :: MTaskDevice -> Shared Channels
  96
  97 class MTaskDuplex a where
  98         synFun :: a (Shared Channels) -> Task ()
  99 \end{lstlisting}
 100
 101 \section{Communication}
 102 All \gls{mTask} messages are encoded following the specification given in
 103 Appendix~\ref{app:communication-protocol}. Available messages are:
 104 \begin{lstlisting}[caption={Available messages}]
 105 :: MTaskMSGRecv
 106         = MTTaskAck Int Int           | MTTaskDelAck Int
 107         | MTSDSAck Int                | MTSDSDelAck Int
 108         | MTPub Int BCValue           | MTMessage String
 109         | MTDevSpec MTaskDeviceSpec   | MTEmpty
 110
 111 :: MTaskMSGSend
 112         = MTTask MTaskInterval String | MTTaskDel Int
 113         | MTShutdown                  | MTSds Int BCValue
 114         | MTUpd Int BCValue           | MTSpec
 115
 116 :: MTaskInterval = OneShot | OnInterval Int | OnInterrupt Int
 117 \end{lstlisting}
 118
 119 \subsection{Add a device}
 120 A device can be added by filling in the \CI{MTaskDevice} record as much as
 121 possible and running the \CI{connectDevice} function. This function grabs the
 122 channels, starts the synchronization \gls{Task}, makes sure the errors are
 123 handled when needed and runs a processing function in parallel to react on the
 124 incoming messages. Moreover, it sends a specification request to the device in
 125 question to determine the details of the device and updates the record to
 126 contain the top-level \gls{Task}-id. All the device functionality heavily
 127 depends on the \CI{withDevices} function that applies a function a device in
 128 the \gls{SDS} when they are equal. Device equality is defined as equality on
 129 their channels. This allows you to give an old device record to the function
 130 and still update the latest instance. Listing~\ref{lst:connectDevice} shows the
 131 connection function.
 132
 133 \begin{lstlisting}[label={lst:connectDevice},%
 134         caption={Connect a device}]
 135 withDevices :: MTaskDevice (MTaskDevice -> MTaskDevice) -> Task [MTaskDevice]
 136
 137 connectDevice :: (MTaskDevice (Shared Channels) -> Task ()) MTaskDevice -> Task Channels
 138 connectDevice procFun device = let ch = channels device
 139         in appendTopLevelTask 'DM'.newMap True
 140                 (procFun device ch -||- catchAll (getSynFun d.deviceData ch) errHdl)
 141                 >>= \tid->withDevices device (\d->{d&deviceTask=Just tid,deviceError=Nothing})
 142                 >>| upd (\(r,s,ss)->(r,s++[MTSpec],ss)) ch
 143         where
 144                 errHdl e = withDevices device (\d->{d & deviceTask=Nothing, deviceError=Just e}) @! ()
 145 \end{lstlisting}
 146
 147 Figure~\ref{fig:handshake} shows the connection diagram. The client responds to
 148 the server with their device specification. This is detected by the processing
 149 function and the record is updated accordingly.
 150
 151 \begin{figure}[H]
 152         \begin{sequencediagram}
 153                 \newthread{s}{Server}
 154                 \newinst[4]{c}{Client}
 155                 \begin{call}{s}{MTSpec}{c}{MTDevSpec}
 156                 \end{call}
 157         \end{sequencediagram}
 158         \caption{Connect a device}\label{fig:handshake}
 159 \end{figure}
 160
 161 \subsection{\glspl{Task}}
 162 \subsection{\glspl{SDS}}
 163 \todo{Connectie, hoe gaat dat in zijn werk}