From: William Hermans <[email protected]> Reply-To: "[email protected]" <[email protected]> Date: Thursday, July 3, 2014 at 1:56 PM To: "[email protected]" <[email protected]> Subject: Re: [beagleboard] Educated Noobie: Should i start with Arduino, or Beagle?
> From what I understand the PRU's( there are two ) operate at 200Mhz, and run > independently from the main processor. Most instructions also from what I > understand take one cycle, and a cycle being 5uS ( someone correct me here if > I am wrong ). 5ns > > > The main processor on the other hand, running Linux we're to expect latency in > the millisecond range. Fast enough for many things but not fast enough for > high speed / resolution PWM / ADC etc. It is my understanding that running a > real time kernel would tighten things up, perhaps a lot. > > Assuming we may think running Linux is beneficial ( and it really can be ) we > can use something like an SBC to handle much of the work that does not require > very low latency. While the tasks that do require very low latency we can > either use 1-2 PRU's, *OR* use external MCU specific to the task at hand, that > stay in communication ( somehow ) with the main board. This main board can > then be used as a communication / control hub internal to the project, and to > the outside world. > > Personally, I struggle with the idea of using Linux myself in several embedded > situations. As in "why do i need to add this complexity", etc. Surely you > could use some development board, or processor tied to a wireless device with > an embedded networking stack. But then you price such devices, and you realize > that you can very easily double, or triple the costs of the BBB. While the BBB > being a Linux computer, if you need wifi, you buy a $12-$15 USD wifi<->USB > dongle, making sure the chipset you chose has good support in your distro of > choice. *OR* since the BBB also has UART, and SPI, you could also use a > wireless device as mentioned above. But again, you're going to double your > costs. > > Passed this, the BBB having the ability to run Linux and thusly being far more > general purpose. It can be used in far more situations. > > Anyway this is just my own thoughts on this topic, and surely there is more to > consider than the tiny bit I covered. > > > On Thu, Jul 3, 2014 at 12:37 PM, Jerry Davis <[email protected]> wrote: >> I really haven't done any serious real-time since my DEC days. >> I was a software specialist for DEC in Dallas, who specialized in real-time >> apps for RT-11 and RSX. >> At that time I was handling in excess of 3000 interrupts per second in >> assembler on a downloadable RSX-11S image. >> This was on old hardware by today's standards, I would think. >> >> For real-time what is expected interrupt rate on an ARM? BBB specifically? >> >> >> >> On Wed, Jul 2, 2014 at 9:56 PM, William Hermans <[email protected]> wrote: >>> The term real time is subjective in this context anyhow. There is always >>> going to be latency, it is just a matter of how much you can put up with. >>> After all we're not talking about some medical device, or Automobile control >>> system. UAV ? >>> >>> But looking at this from an automobile perspective, you have a main computer >>> system with many MCU's Performing sometimes critical tasks, and >>> communicating back and forth with this main system via CANBus. >>> >>> The OP really needs to define "Robot" more clearly. I mean we're not talking >>> about an AT-AT walker model with stepper motors, while also having the >>> ability to walk around are we ? . . . >>> >>> >>> >>> On Wed, Jul 2, 2014 at 5:30 PM, Robert Nelson <[email protected]> >>> wrote: >>>> On Wed, Jul 2, 2014 at 7:28 PM, Jerry Davis <[email protected]> wrote: >>>>> > I have used BBB, RPi, and arduino. >>>>> > >>>>> > arduino is closer to real-time if you need that. However, it does only >>>>> what >>>>> > is programmed in C in a loop fashion. There is a setup() function and >>>>> loop() >>>>> > function. >>>>> > just about everything is done in the loop. If you need tight integration >>>>> > (real-time) with some piece of hardware, then arduino is the way to go. >>>> >>>> Unless you use the "pru" on the bbb.. ;) >>>> >>>> Regards, >>>> >>>> -- >>>> Robert Nelson >>>> http://www.rcn-ee.com/ >>>> >>>> -- >>>> 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] >>>> <mailto:beagleboard%[email protected]> . >>>> For more options, visit https://groups.google.com/d/optout. >>> >>> -- >>> 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. >> >> >> >> -- >> Extra Ham Operator: K7AZJ >> Registered Linux User: 275424 >> Raspberry Pi and Arduino developer >> >> There are 10 kinds of people in the world: >> Those who can read binary and those who can't. >> -- >> 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. > > > -- > 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. -- 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.
