DIY Project Solution: BBB vs RPi+Arduino

Hi Drew,

Interesting topic! As I understand, most telescope positioning uses high-res optical encoders, so having a high-speed processor dedicated to counting pulses is really good I think, and use the other to control the motors.

It is more convenient outdoors to run the BBB from a Li-Po cell since it has a built-in charger (I need to make this a blog post because it gets lost) than a RPI which needs a more inconvenient supply.

LCDs are easily connected for selecting the desired object on either platform, but capes already exist for the BBB, or use a mobile/tablet for the UI. If not wifi, then possibly USB OTG cable from an android device, to the BBB - not sure if that is possible with an RPI.

The tables for star positions, and the formulas for planetary motion are all open source since this information is as old as astronomy, and it is not difficult to compile for Linux. It would run faster on the BBB most likely.

I'm not sure if many astronomers use CMOS now, maybe they do. However, there are some CCD cameras and decoders that connect via USB, and so possibly a good USB capability is needed for the high-speed data. At any rate, the ability to be able to select the sensor is important (whether that is CMOS or CCD), so a good USB capability is important. Or, for reduced cost but still high performance, a lower cost analog CCD cam could be interfaced.

I totally agree with your analysis and comments. At first the Rpi may look more attractive from a price standpoint, but when you start to analyse the architecture and features, the BBB is a much better and cost effective platform.

Don't forget the both the BB and BBB have a native ethernet interface on the AM335x not as an external add-on via a USB interface with not fully functional drivers like the Rpi.

I'm getting more often the same question, particularly people interested to do more IO stuff, so besides the hype and popularity that was created around the Rpi that is just a toy promoted as a "computer" based on a GPU with an old ARM core, the BBB is a much more suitable platform for many DYI projects.

Many times an important aspect of developing interfaces is to have at minimum the electrical characteristics and functionality of each pin, unfortunately Broadcom didn't release that information and trying to fix these limitations with an Arduino, not good either.

I'd certainly recommend the BBB.

My .02

Jorge

That's sound advice for your friend, Drew.  Pi would match astronomy requirements very poorly, if at all.  Embedded control applications such as this are really BBB's target market, and it shines there for all the reasons you listed.

shabaz wrote:

 

It is more convenient outdoors to run the BBB from a Li-Po cell since it has a built-in charger (I need to make this a blog post because it gets lost) than a RPI which needs a more inconvenient supply.

That's a very good point.  Battery backup would be an excellent feature for telescope electronics and also for a whole observatory, as power loss could ruin a time exposure or even a whole night's observing session.  The BBB's Li-Po ability provides an easy start in that direction.

Yes please on the blog article.

If you have additional info on the BBB's charging characteristics or electronics, that would be very cool, but even if you just resubmitted your (already very informative!) discussion post, it would give this important topic greater visibility.

Maybe we should suggest to Jason/Gerald that  providing a mounted Li-Po socket on the next colour of BB would be an attractive bullet point for embedded projects, and it would have minimal effect on BOM costs.  The mod is easy, but even simple soldering is a hurdle for huge numbers of people.

Addendum:  I've been thinking about ways of routing the Li-Po path through a cape with the purpose of V and A monitoring by the BBB, not only of its own power but also of multiple external supplies and sinks.  Having its own backup power would make it a very effective power monitor and manager for a system, able to survive target voltages dropping all the way to zero even if it's normally powered by them.

I see that one UK supplier was doing the BBB for £23 so in fact even cheaper than the Pi in this case.

More I look the more impressed with the BBB...I really like the run from LiPo Idea

Well that's done it ordered my first BBB from CPC !

Is there much in the way of examples for the CAN bus ... My first project is for a Car would be nice to read the basic info direct from the vehicle .

John Alexander wrote:

 

Well that's done it ordered my first BBB from CPC !

Oh dear, better fit a lock to your wallet quick.  You'll understand why once they start sending you their catalogues every few days.  It's a very dangerous site. 

Oh, I missed it! It's £30.99+vat now.

Done! Added a blog entry (as you guessed, I planned to have some more information, but it may be sufficient for now anyway).

It's a good point that you mention, it would be worthwhile to alert them that a connector on their next board design would be great.