Re: GNAT.Serial_Communications

[tonyg <tonythegair@gmail.com>]

On Apr 19, 8:57 pm, "Alex Mentis" <f...@invalid.invalid> wrote:
> Ludovic Brenta wrote:
> > I think you'll have to create a task-specific binding to ioctl(2) to
> > set the flow control options before writing to the port.  
>
>  ...
>
> > If you're not sure what arguments to pass to ioctl, maybe you can try:
>
> > strace stty --file=/dev/ttyUSB0 -crtscts
>
> Does anyone know if the code below would work? I don't have a Linux box
> handy here, so I can't test it myself. I'm just going off of some notes
> on forking Linux child processes I acquired -- I've never actually done
> this, myself....
>
> ** begin code **
>
> with Ada.Text_IO; use Ada.Text_IO;
> with Interfaces.C;
> with Interfaces.C.Strings;
>
> procedure Main is
>
>    procedure Config_Stty is
>
>       package C renames Interfaces.C;
>
>       -- create an array that contains each portion of the command
>       -- to be executed
>       -- array must contain a null pointer in the last element
>       Stty_Cmd : C.Strings.Chars_Ptr_Array :=
>                    (C.Strings.New_String ("stty"),
>                     C.Strings.New_String ("--file=/dev/ttyUSB0"),
>                     C.Strings.New_String ("-crtscts"),
>                     C.Strings.Null_Ptr);
>
>       -- create an Ada-style prototype as an interface to the C execvp
>       -- function and associate the two with an Import pragma
>       procedure Execvp (File : C.Strings.Chars_Ptr;
>                         Args : C.Strings.Chars_Ptr_Array);
>       pragma Import (C, Execvp, "execvp");
>
>       -- create an Ada-style prototype to the C fork function so
>       -- you can call execvp then resume this program's execution
>       function Fork return Long_Integer;
>       pragma Import (C, Fork, "fork");
>
>       -- create an Ada-style prototype to the C waitpid function so
>       -- the parent will wait until the forked process completes
>       procedure Waitpid (Pid : Long_Integer; Stat_Loc, Options :
> Integer);
>       pragma Import (C, Waitpid, "waitpid");
>
>       Pid : Long_Integer;
>
>    begin -- Config_Stty
>
>       Put_Line ("Configuring serial port...");
>
>       -- create child process
>       Pid := Fork;
>
>       if Pid = 0 then -- I'm the child process
>          -- call execvp with the stty command
>          Execvp (Stty_Cmd (Stty_Cmd'First), Stty_Cmd);
>          -- Execvp does not return unless there's an error;
>          -- should probably check for that here and raise exception on
> error
>       elsif Pid > 0 then -- I'm the parent process
>          Waitpid (Pid, 0, 0);
>          Put_Line ("Continuing execution...");
>       else -- if Fork returns -1, then it was unsuccessful
>          Put_Line ("Unable to create new process.");
>       end if;
>
>    end Config_Stty;
>
> begin -- Main
>
>    Config_Stty;
>
>    -- serial port's ready to go; do the rest of your stuff here...
>
> end Main;

I don't think this would work because the port's settings need to be
overwritten after it is opened, as Gnat sercom will open it with
control flow enabled. I suspect it may be best to modify the serial
communications package so that there is a control flow option within
the set port procedure. Or to make a copy of the sercom package, call
it something else, modify that and use it.