On Monday, August 24, 2015 at 5:39:54 PM UTC-7, Charles Steinkuehler wrote: > > On 8/24/2015 6:12 PM, Andrew P. Lentvorski wrote: > > I've been trying to hunt down the maximum frequency on the BeagleBone > Black > > GPIO pins. > > > > This *seems* to be dominated by the transaction latency across the L3/L4 > > interconnect. Fair enough. So ... > > > > What's the latency number? > > > > I've *measured* about 166ns per transaction (I can create a roughly 3MHz > > toggle which is 2 pin flips which requires 6MTransactions/s which is > > 166.66ns per transaction). But I don't know how to *calculate* that > number > > from the documentation. > > I've measured 40 ns from the PRU. I'm not sure if the CPU can match > this, but I'd be surprised if it couldn't. >
Well, there could be some silliness involving the fact that the memory is mmap'd in Linux. A TLB access or something similar might be required that could add overhead. This is a bit lower level than you'll find in most reference manuals, > and falls into the category of "if it's _really_ important to you, > contact the manufacturer and verify"...and I hope you're buying a > *LOT* of parts, because this is the sort of thing that is subject to > change with die revisions. :) > It actually surprises me that this information isn't documented. However, I presume it's because most people using this high-end a processor really only use the peripherals. The only thing most people really use the GPIO's for is generating interrupts. I suspect I could live with things as they stand, but this is really going to make things ... annoying. I may be better off just trying to do nasty things to the McSPI subsystem. SPI really doesn't like bi-directional data lines, though. -- 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.
