Re: Raspberry Pi, Real-Time and Ada

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

On Friday, February 7, 2014 6:28:23 AM UTC-2, Stephen Leake wrote:
> Ok, good.
> What is your application?

In short, drones. 

> What are your timing requirements?
For the next application I think I will need achieve 1 ms for I/O access in hard RT, and up to 100 us for pure computation for soft RT.

> I think you are asking:
> "How do you know the RPi can meet 0.1 second tolerances?"
> I've seen one running Emacs, and it responds well to keyboard commands.
> Humans notice delays longer than 0.1 seconds, so that's my metric.

Ok, it makes sense. In this case, I also get to run GPS on it, and I cannot feel any delay to the keyboard.

> Why do you think 0.1 seconds is "slow"?
> If the application is flying a spacecraft to Jupiter, then 1 day is
> "fast" during the coast phase, when nothing much is happening.
> "fast" and "slow" are totally determined by the application.

Indeed. Yes, I will need much faster.

> That's heavily application dependent.
> If your application is some sort of control system, then it reads
> inputs, computes, and writes outputs.
> Using an oscilloscope, measure the time from an input signal to a
> related output signal.

I was thinking more on some sw tools made for measuring hw performance. A time ago I used some tools for evaluating performance of parallel machines with MPI and OpenMP (I don't remember the names now), thought it could have some of these in RPi. Anyway measuring the outputs would be a very good starting point.

--
Rego.