Kent A. Reed wrote: > > What with the differences between different IP cores from ARM Holdings, > different CPUs from licensees of the IP cores, and different boards > integrating lots of other stuff to these CPUs from folks like > BeagleBoard, the Raspberry Foundation, etc., I am in a state of > perpetual confusion:-) > > Yes, you really have to select one, based on insufficient info, and try to make it do something useful. There will be a new board every couple months (like Beagle now has 3 products, all significantly different.) > It's nice that the latencies you are seeing with your Raspberry PI seem > comparable to the latencies Jon Elson reported earlier for his > BeagleBoard so maybe we are slouching toward daylight. > I have not reported any thread latencies for the Beagle. I do know quite a bit about using the GPIO and the bare performance of that. I have never run an RT kernel on the Beagle, but would be very interested to know about the latency and also floating point performance of the system. As for interrupts and timers, if you accept that you have to add FPGA hardware to the CPU for step generation, encoder counting or whatever, then you can have that add-on produce the interrupts for the RT thread at any rate you choose. If you are going to use the 10 KHz timer of the Pi, then you could divide down and only do the servo thread every 2, 5 or 10 ticks of the timer.
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