Raspberry Pi or Beagle Board!!??

What is your application ?

Michael Kellett

What is your application ?

Michael Kellett

I am starting. Apart from Price, what are the characteristic differences? use for robotics and real-time embedded application.

I don't think I would use either for what I would call a real-time embedded application but the defintion of real-time is very vague.

from Wiki: systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response

But on that basis almost everything is  a real time system.

So the Beagle and RPi are OK for deadlines in the order of 10s of mS, less with some hard work, but they don't (normally) use a real time OS.

But you should do your own research - download the data for both boards - compare them with each other and your specification.

No one can help you unless you describe your project in a lot more detail.

Michael Kellett

Michael Kellett wrote:

 

I don't think I would use either for what I would call a real-time embedded application but the defintion of real-time is very vague.

 

from Wiki: systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response

 

But on that basis almost everything is  a real time system.

That's absolutely not the case.

Almost nothing is a real time system.

real-time is about meeting the deadline or missing the deadline as in event occurs at time X. Deadline is at X + 30ms.

In case of hard real-time if the deadline is missed somebody might get hurt or die (airplane, car, robots etc.).

In case of soft real-time if the deadline is missed it's inconvenient (video streaming, voice over ip etc.).

@ Baba,

You have provided your own peronal definition of hard real time - can you back it up with any references ?

To back up my own comments:

Hard real-time systems are ones in which correctness depends on execution

occurring within a fi xed period of time [GR04]. Surprisingly, most previous re-

search in runtime monitoring focuses either on non real-time programs or soft

real-time systems, in which occasionally missing deadlines is tolerated.

(from a paper presented at International Conference on Runtime Verification 2010)

Hard or softness of real time is not a measure of the importance of systme failure.

Michael Kellett

In my experience, the term "real time" is relative.

If your requirements have a specific time response number, then that becomes your real time event to design to.

If you cannot measure the response, then it is not real time.

After you establish your real time event, you have to do a criticality/risk assessment as to the effect of missing the defined response time.  In either case, you have to have a strategy for dealing with the lost event, should it occur.

In systems engineering, we had to go through every system event until we could show that the system reached a specific level of survivability for a specific cost.  It was only after that analysis  that the system functions were allocated between hardware and software.  When software was not fast enough, you go to a hardware solution.  It may not be the most versatile, but it can usually meet any realtime constraint.

The same goes for selecting the computer processor.  You have to pick one that when combined with the software has enough capability to meet the requirements allocated to it.  In advanced applications, you often are limited in your candidates to select from, so you need to understand your choice in very great detail.

Now back to the topic, the selection between PI and BeagleBone depends upon your requirements.

If both satisfy your requirements, then you look at the expense of the development environment.  Sometimes the cheaper processor carries the highest cost to develop.  The worst thing you can do is try to pit one against the other without a defined set of requirements.

Thats the truth for all processor selections.  It is more than just selecting the board.  You have to look at the bigger picture of your intended application and understand that whichever one you choose, it will be obsolete before it gets delivered.

I hope I have added enough confusion to the original question, but I have worked on many state of the art realtime systems.  If you do not fully understand your requirements, you will fail. 

I successfully implemented a lot of systems in applications where people said that you could not do the job in software.  The requirements are the key.  Understand them and you will be successful.  Ignore them and you will fail.

As stated by the gospel of DAB.

Just my opinion.

DAB

Note that the BeagleBone has 2 200MHz 32-bit RISC microcontrollers (programmable real-time units or PRUs) that can be programmed with an open source assembler to perform real-time tasks.  The typical approach on Raspberry Pi to handle low latency is to add an Arduino.  That's also been the popular approach on BeagleBone until somewhat recently with a lot more activity with 3D printers using the PRUs.  http://github.com/beagleboard/am335x_pru_package.

hi sir michael kellett...

which is better to use in displaying the content of a flash drive to an LCD(touch screen)?

Hi Jem

For either, it would depend on those contents and their media intensity (photos, videos, file lists, etc). You'd need to get an expansion or shield for the RPi or BB in order to do it.

You could also look at solutions that include touchscreens to start with. At Gumstix we have the Pepper Package, which is currently our only SBC, and includes a touchscreen display, AM3359 processor, 802.11b/g/n wi-fi, and gigabit ethernet. Based on the limited information you provided, it would probably fit the bill and give you flexibility for future projects.