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Serial DOS
4.7.7 Command Line Input
There are a number of different ways that you can "scan" the parameters that start the
program. For example, if you start a simple terminal program in DOS, you can use this
command to begin:
C:> terminal COM1 9600 8 1 None
or perhaps
C:> terminal COM4 1200 7 2 Even
Obviously there should not be a need to have the end-user recompile the software if they
want to change something simple like the baud rate. What we are trying to accomplish here
is to grab those other items that were used to start the program. In Turbo Pascal, there is
function that returns a string
ParamStr(index)
which contains each item of the command line. These are passed to the program through
strings. A quick sample program on how to extract these parameters can be found here:
program ParamTst;
var
Index: Integer;
begin
writeln('Parameter Test -- displays all command line parameters of
this program');
writeln('Parameter Count = ',ParamCount);
for Index := 0 to ParamCount do begin
writeln('Param # ',Index,' - ',ParamStr(Index));
end;
end.
One interesting "parameter" is parameter number 0, which is the name of the program that
is processing the commands. We will not be using this parameter, but it is something useful
in many other programming situations.
4.7.8 Grabbing Terminal Parameters
For the sake of simplicity, we are going to require that either all of the parameters are going
to be in that format of baud rate, bit size, stop bits, parity; or there will be no parameters
at all. This example is going to be mainly to demonstrate how to use variables to change
the settings of the UART by the software user rather than the programmer. Since the added
sections are self-explanatory, I'm just going to give you the complete program. There will
be some string manipulation going on here that is beyond the scope of this book, but that
is going to be used only for parsing the commands. To keep the user interface simple, we
are using the command line arguments alone for changing the UART parameters. We could
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