Re: GNAT.Serial_Communications

["Alex Mentis" <foo@invalid.invalid>]

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;