> On Sep 21, 2015, at 22:58 , Larry M <[email protected]> wrote:
>
> 1) In the future, how should I upgrade without losing all of my files? How
> do the pros do it? I notice there is now a 9/20/2015 eMMC flasher update and
> would be interested in updating as long as I don't lose my files. Will a
> simple apt-get update command do the job, or is there something more subtle I
> should do? Sorry for the ignorant question, but I've been unsuccessful in my
> internet googling so far...
I don't have a good answer here, as I'm not well-versed in Linux distros in
general. However, I routinely see people apt-getting the kernel to update that.
> 2) Completely different topic. I am interested in a realtime Kernel. I will
> be using the BBB for a 200 Hz closed-loop control application, and need
> reasonable assurance of a 5 msec time step. I noticed that the 9/13/2015
> build I grabbed has PREEMPT enabled. Maybe this is good enough?? (An
> occational missed frame isn't the end of the world...) If PREEMPT isn't good
> enough, I notice plenty of instructions on the web about compiling the
> RT-PREEMPT Kernel, which seems like a dangerous prospect to a newcomer such
> as myself. Will I really need to compile the Kernel to get this
> functionality, or is there an easier way?
I can try to answer the second question for you. I don't know enough about
real-time kernels to suggest that route, but you should consider the BBB's two
PRU cores (programmable real-time units). On the AM335x Sitara processor on the
BBB are two additional, independent 200 MHz 32-bit CPU RISC cores. You can
write C or assembler code and program them "bare-metal." They have access to
shared memory with each other and the ARM core, can send and receive
interrupts, and access all the peripherals and GPIOs (some GPIOs are "fast").
There's a bit of a learning curve in setting them up, and while I had them
working on a 3.8 kernel, I have not been able to get them working on 4.1 (I'm
sure I've just overlooked something stupid). But they're extremely versatile
and really elevate the BBB's capability.
There are numerous bits of documentation floating about. Here are some:
http://processors.wiki.ti.com/index.php/PRU_Training:_Hands-on_Labs
https://github.com/beagleboard/am335x_pru_package
http://www.element14.com/community/community/designcenter/single-board-computers/next-gen_beaglebone/blog/2013/05/22/bbb--working-with-the-pru-icssprussv2
http://elinux.org/BeagleBone_PRU_Notes
Robert C Nelson produces all the distros, and has apt-get repos that provide
the am335x-pru-package you can install via apt. Oh wait, the Debian distro
already has them configured.
sudo apt-get install am335x-pru-package
Hope that helps.
--
Rick Mann
[email protected]
--
For more options, visit http://beagleboard.org/discuss
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