On 09/30/2013 12:05 PM, Leonardo Marsaglia wrote: > Hello to all. > > I need to control a screw with an encoder mounted on it. Calculating the > max rpm and the resolution I want I need a 25 khz read response for the > encoder. > > I remember reading somewhere the maximum expected frequency of the parport > software driver to read an input but I don't remember where. > > I would like to know please if any of you have an approximation of the > frequency, because If this works I can save some money. If not, I would > have to buy dedicated hardware. > > The port, itself, has no frequency limit. It takes about 1 us to read the legacy ports, and the motherboard puts the CPU in a wait state while it is doing it. But, reading a single register of the parport hardware will just take about 1 us, at the lowest level. The hal_parport driver is fairly efficient, and you only need one instance of the software encoder component should also be fairly efficient. If you need to detect position every 25 us, this could be a problem. If you just want to be sure that encoder counts are not lost, then this should work fine.
Later motherboards with PCI-connected parports are a bit faster. You should be able to run a 25 us (25000 ns) base thread on a good CPU. Jon ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
