Re: Raspberry Pi, Real-Time and Ada

["Rego, P." <pvrego@gmail.com>]

> I don't think that 10ms would be a problem even for ARM.
> On an Intel board 200µs loops (read inputs, calculate, write outputs) are
> doable.
> Ada has everything you need for that.
> The main problem is how good the RT clock is. Windows and VxWorks typically
> have miserable RT clock services on x86. x86 Linux has a decent one.
> Regarding ARM Linux, I didn't tested its clock, so I cannot tell. The
> primary test is to call Ada.Real_Time.Clock twice and to compare if the
> reading is same. If they are you should look for an alternative
> implementation of. 

BTW, now I have done a fast test using 

with Ada.Real_Time; use Ada.Real_Time;
with Ada.Text_IO;

procedure My_Clock is
   First_Time : Time;
   Second_Time : Time;
   F_Duration : Time_Span;
   Time_Duration : Duration;

begin
   First_Time := Ada.Real_Time.Clock;
   Second_Time := Ada.Real_Time.Clock;
   F_Duration := Second_Time - First_Time;
   Time_Duration := To_Duration (F_Duration);

   Ada.Text_IO.Put_Line (Duration'Image (Time_Duration));  

end My_Clock;

and the result was in average 17us for the RPi (with Raspbian without the preemptive patch), with a variation of 1 us (for just a few executions), while the same code running on a Windows 7x64 machine was sometimes 0, sometimes 366ns (49 times faster).