> On Jun 15, 2015, at 07:33 , Bill M <[email protected]> wrote: > > To Rick M, one of the things that attracted me to the BBB was that it has > several available UARTS, but I also need things to run in a deterministic > fashion since I need to control an array of servos and updating needs to > happen 128 times a second, which means a several dozen byte packet going out > that frequently. After reading through a bit more in the TRM about the PRU > UART, I don't think a PRU UART will be feasible since it looks like they top > out at around 300Kbs, and I need a megabit. I'm hoping things will be > sufficiently deterministic since I'm running bare metal, and will drive the > update loop with a timer interrupt and have the UART just feed things out as > fast as the line will consume it. I know things will run more slowly if I > don't use caching, but if I disable caching, does that eliminate any > pipelining? I'm a noob when it comes to pipelining and caching, since I've > only ever hacked on AVR microcontrollers and a Cortex M3, where those weren't > considerations. I'm a line of business programmer in my day job :(.
I'm not sure exactly what you're using the UART for. Are your servos controlled via serial packets of some kind? Or are they typical hobby PWM servos? If the latter, then I would have thought using a UART on the ARM core (not the PRU) would be the best way to go. I'm assuming they can do a megabit, although that probable requires DMA. It sounds like you're using the UART to communicate with the servo, and a high rate. I can see why you'd want the timing to be right in that case. I don't really have any idea what the caching effects are. Good luck! -- Rick Mann [email protected] -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
