1 The only thing the microcontroller has to communicate back with the server is
2 an update of the SDS and a request for an SDS value.
3 Since all SDSs have a numeric identifier the engine can just send a request
4 message with the identifier to the server. A detailed description of the
5 message for sending and receiving SDSs is described in
6 Tables~
\ref{tbl:sdssend
},~
\ref{tbl:sdsrecv
}.
8 As said before, publication of SDS values is not done automatically to save
9 bandwidth. Therefore the tasks need to have a way of requesting the latest SDS
10 value and a way of publishing an updated value. This is elaborated more upon in
11 the next section.
\todo{Type safety of SDS access
}
19 \multicolumn{2}{c
}{\textbf{Request
}}\\
20 $
1$ & SDS send code
\verb#'s'#\\
21 $
2-
3$ & SDS identifier as a
16-bit integer\\
22 $
4-
5$ & Length of the message
16-bit integer\\
23 $n$ & Value of the SDS identifier\\
26 \caption{Message format for a SDS-send operation
}\label{tbl:sdssend
}
35 \multicolumn{2}{c
}{\textbf{Request
}}\\
36 $
1$ & SDS send code
\verb#'r'#\\
37 $
2-
3$ & SDS identifier as a
16-bit integer\\
39 \multicolumn{2}{c
}{\textbf{Response
}}\\
40 $
1-
2$ & Length of the message as a
16-bit integer\\
41 $n$ & Value of the SDS\\
44 \caption{Message format for a SDS-receive operation
}\label{tbl:sdsrecv
}