On Mon, Jun 15, 2015 at 4:48 PM, Rick Mann <[email protected]> wrote:
> > > 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. > > Interesting - - - servos - - - suggestions for non-hobby servos? I am looking at a robotics project where I need commercial (full industrial) reliability and and and. Just getting into this stuff so I have spent most of my time so far just reading (hopefully learning and not asking superfluous questions! grin!!). TIA Dee -- 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.
