Pi vs BeagleBone-Black

I'd like to add another pro for the BeagleBoard Black.

With the exceptions of the integer real time processors PRU-ICSS (not sure at this point why that is), and the PowerVR GPU for

well known reasons, the AM3359 technical documentation from TI is excellent to the point of overwhelming. The Technical Reference

Manual is over 4000 pages. No I did not accidentally add any zeros !

Gary Stewart wrote:

 

With the exceptions of the integer real time processors PRU-ICSS (not sure at this point why that is), and the PowerVR GPU for well known reasons, the AM3359 technical documentation from TI is excellent to the point of overwhelming.

You're right about the proprietary GPU, that seems to be an endemic problem for open source in the industry.  It's not true for the PRU-ICSS though.

The PRU-ICSS is fully documented in the Technical Reference Manual SPRUH73C, with the entirety of chapter 4 (250 pages) devoted to it.  Also, there is a full package of PRU-related materials on Github, including more documentation and source code of the PRU's PASM assembler, a Linux loader, demos, etc.  I've even checked that the assembler compiles and it does.

The BeagleBone materials on Github are at https://github.com/beagleboard/am335x_pru_package

The PRU has been used successfully in quite a number of projects as a quick web search shows, and this long predates the BeagleBone Black since the original BeagleBone uses a slightly different version of the same AM3359 SoC.

Morgaine.

Addendum: Repeating the link to TI's wiki pages on PRU which I gave in my first post on this thread, in case it was missed when looking for docs.  There is a developers' link at the bottom of that first page.

> The intended R-Pi market was always very narrowly defined (very low cost computer used to teach kids about computers).

Education was the stated goal of the RPF, but not necessarily their marketing focus prior to

the yet-to-be-released educational release.  I see a lot more marketing effort focused on

Maker Faire venues than educational venues.   Early on, they hired an educational person,

but quickly let her go without a replacement until recently.

> The main drawback I see for the BB Black as far as video goes is the 16 bit memory data bus vs 32 bit for the Pi.

I think you also need to consider memory caches and data paths.

On the RPi, the cpu has to go through the gpu to access memory and cache.

I suspect the BBB has a better caching system.   There are memory benchmarks

that might be useful, such as

http://lmbench.sourceforge.net/

coder27 wrote:

> The intended R-Pi market was always very narrowly defined (very low cost computer used to teach kids about computers).

Education was the stated goal of the RPF, but not necessarily their marketing focus prior to

the yet-to-be-released educational release.  I see a lot more marketing effort focused on

Maker Faire venues than educational venues.   Early on, they hired an educational person,

but quickly let her go without a replacement until recently.

> The main drawback I see for the BB Black as far as video goes is the 16 bit memory data bus vs 32 bit for the Pi.

I think you also need to consider memory caches and data paths.

On the RPi, the cpu has to go through the gpu to access memory and cache.

I suspect the BBB has a better caching system.   There are memory benchmarks

that might be useful, such as

The focus still seems to pretty heavy on education however given the new opportunities that opened up, things changed. I still see a heavy interest

from the RPF in education though. They just seem to be relying more on outside help and they always said that they wanted that too.

I do consider caches and data paths but I assume they both have video and CPU caches so I see no advantage either way there. Displaying video

must have top priority otherwise the display will have artifacts and that would not do at all. For this reason it makes sense that the memory path to

the CPU in the Pi runs through the video section first. Sooner or later (and probably fairly often) there is going to a miss in all caches and filling sets

of tag lines (video first, always) through a 16 bit data path is a major bottleneck. Even with the 32 bit data path I'm fairly confident that this is a major

reason as to why the Pi seems sluggish most of the time even when it is overclocked to 1 GHz. I don't see how a 16 bit data path can be made to

improve that.

I will never been a big fan of the CPU and video sharing memory on motherboards. For low cost solutions using SOC's it makes more sense but at

a (literally) noticeable cost.

Morgaine wrote:

and the gratification is not instant because the newbie "hurdle" of writing the SD card still has to be overcome.

Every company that I know of that sells the Pi offers pre-programed SD cards too.

Guys/gals

This is a much better debate ...well done.

Thanks for the responses re the comparisons/features.

A new user looking to compare them still has to read through lots of discussions in order to draw a list.

Do we have a means of producing a table with perhaps 4 columns

Pi A, Pi B, BB, BBB

something similar to the table of Page 10 of the datasheet found here.

(interesting it says not for dissemination)

http://nz.element14.com/circuitco/bb-bblk-000/beaglebone-black-cortex-a8-dev/dp/2291620

since E14 are selling both/all it shouldn't be hard to have a page that can be edited, or should we tackle a WIKI page that is maybe moderated.?

The points made about extras are also worthy of note, and while obtaining a preprogrammed card v downloading and programming are noted, it shouldn't be beyond the realms of nearly anyone, as long as the instructions are clear (last time I looked they were).

For the video discussion, that information can be included with a 'plain english' note suggesting more/less suitable as a media centre, or something that gives information to someone whom frame count and bit numbers mean nothing to.

One thing is clear from the Pi entry into the market, it has brought change, and more affordable hardware to the reaches of more people.

Be that technogeeks (no offense) or ordinary interested people.

Also can someone please explain the fascination with Antoids tins.

The KL25z apears to also fit, although I'm not sure why you'd use a metal tin to house a bare pcb that needs external connections in order to function, and generally will have a display or leds that somehow need to get through to the outside world.

cheers

Mark

PS I will probably add a BBB to my other controllers, but in the meantime I have too many other things on to use in in anger.

This doesn't mean that new users have the luxury and may need good information as their purchasing ability is lacking.

Mark Beckett wrote:

 

The KL25z apears to also fit

While it fits in the tin, it doesn't fit in the group.

Just to clarify that the mention of KL25Z wasn't to rank the Freedom board alongside BB and Pi.  For the benefit of new readers ...

Microcontrollers like the KL25Z/Cortex-M0+ are in a different category to application processors like the BCM2835/ARM11 or AM3359/Cortex-A8, which is why manufacturers use those two different terms as marketing slots.  ARM even formalizes the distinction in their naming now, Cortex-M (or R) series versus Cortex-A, which is much clearer than the terminology they used back in the days of ARM9 and ARM11.

Boards like the Freescale Freedom KL25Z belong in the microcontroller group alongside ST's STM32F4-Discovery and the zillion forms of Arduino.  The SoCs in this group typically do not provide an MMU (at best they may provide an MPU with a small number of segments like 8), and so they cannot properly support full operating systems with strong process separation.  That's why they're nearly always programmed either as bare metal or running an RTOS designed for microcontrollers.  (The special uClinux variant can run on them, but its use has decreased markedly now that application processors are common.)

Application processors have proper MMUs and so can run full Linux or other process-protected operating systems.  They're best considered separately, so your suggestion of "Pi A, Pi B, BB, BBB" is a cohesive set since they all employ application processors.

Morgaine.

Mark Beckett wrote:

 

Also can someone please explain the fascination with Antoids tins.

The KL25z apears to also fit, although I'm not sure why you'd use a metal tin to house a bare pcb that needs external connections in order to function, and generally will have a display or leds that somehow need to get through to the outside world.

I'll have a go.  Developer boards (almost) never have cases.  This is probably because while it's very cheap to manufacture cases in quantity, the tooling for the first one is expensive.  Plus, if your target audience is makers, those makers are perfectly capable of making their own cases.  Makers like to take objects they already have and re-purpose them.  Creative use of things that would be otherwise thrown out scores Karma points, or something like that.

RasPi is frustrating because while its rectangular dimensions are the same as a credit card, its square corners prevent it from fitting in an Altoids tin.  Plus, even if you could fit it in, having connectors on five sides (if you include GPIO) makes an Altoids tin problematic.  RasPi only has two "mounting" holes (zero on the rev 1.0 board), which makes a metal case problematic.  BBone has rounded corners so it fits nicely in the case and the four mounting holes make sure you don't short to the metal case.  Having standard I/O jacks only on the ends is very nice.  OTOH, as soon as you plug in a cape it no longer fits.

I far prefer a metal case to plastic.   While EMI shouldn't be a problem with well-designed boards, plastic is a thermal insulator and I'd rather have something that conducts heat and acts as a radiator.  The RasPi model B rev 1.0 sometimes ran quite hot before rev 2.0 fixed an electrical problem and improved the thermal design for the LAN9512.  IMO rev 1.0 is not something that you want to put in a closed plastic or wood case, and rev 2.0 still generates the same amount of heat overall and would get hot in a closed case.  It will work for a while, but excessive heat shortens the lifetime of any electronic device, particularly if you thermal cycle it.

Now for BBone, one should use a YipYap box instead of Altoids.  I think they're the same size.

Mark Beckett wrote:

 

Also can someone please explain the fascination with Antoids tins.

Peergroup reinforcement among techies.

Mark Beckett wrote:

 

This is a much better debate ...well done.

Thanks for the responses re the comparisons/features.

 

A new user looking to compare them still has to read through lots of discussions in order to draw a list.

Epigram #48 from Epigrams in Programming by Alan J. Perlis is:

The best book on programming for the layman is Alice in Wonderland; but that's because it's the best book on anything for the layman.

Let's see what Alice's Adventures in Wonderland has to say on the topic.

"Cheshire Puss," [Alice] began, rather timidly... "Would you tell me, please, which way I ought to go from here?"

 

"That depends a good deal on where you want to get to," said the Cat.

 

"I don't much care where--" said Alice.

 

"Then it doesn't matter which way you go," said the Cat.

Same with RasPi and BBone.  It does depend on what you want to do with it, though as Morgaine pointed out the difference has narrowed with BBone Black.

One thing I would strongly recommend to anyone considering either board -- or any community-supported development board -- is to first spend some time at the forums available for that board.  See how active the forum is, and whether people are getting helpful responses to problems or are being told to RTFM (without providing link to said manual), or worse, "Google it" as if a newbie can tell which few of the 1000 Google results are actually useful.  If you have questions, these are the people who are going to help you -- or not.  Find out if people are having issues with the board and whether you want to face those same issues.  Also, check out the wiki for the board.  It will tell you if people are interested enough in the board to build up a good wiki and are therefore more likely to be interested in helping you when you get in trouble.

Morgaine

Yes thanks for explaining the KL25z wasn't part of the discussion of Pi v BB.

It was just the size.

John

You have some good reasons ...obviously the Antoid tins are a household item on the other side of the world, hence the inital reason.

I also like your advice on the forums/support.

Morgaine

I think your answer is probably what I expected.

I had to ask though.

Yay, more boards with rounded corners! And cheap too!

Not on topic though, except for the rounded corners and the Element 14 angle.

Yay, more boards with rounded corners! And cheap too!

Not on topic though, except for the rounded corners and the Element 14 angle.

Morgaine Dinova wrote:

 

Yay, more boards with rounded corners! And cheap too!

 

Not on topic though, except for the rounded corners and the Element 14 angle.

I like the way the Farnell site shows availability as "Awaiting Delivery" -- sounds like we're expecting a "bundle of joy" .  The USA Newark site just says "Availability: 0" -- no poetry at all.

John Beetem wrote:

 

I like the way the Farnell site shows availability as "Awaiting Delivery" -- sounds like we're expecting a "bundle of joy" .

Better not give Marketing ideas, I really don't want to have my boards delivered with nappies and baby powder.

Here in NZ its 4 times the price of KL25z, but with less features.

Maybe nappies and baby powder will help sell it.

Mark

Hehe.

I don't know PSoC4, but a quick glance at Element 14's linked summary suggests that it's along the lines of PSoC5, which John has often described here (in CPLD/FPGA threads) as being a microcontroller SoC with partially documented programmable logic features.

That makes this board rather eclectic and somewhat alienating to those who prefer traditional CPU software programming.  Perhaps the manufacturer is trying to dispell that image by releasing the board at prices that fall below the worry radar ... except in NZ, that is.

Morgaine Dinova wrote:

 

I don't know PSoC4, but a quick glance at Element 14's linked summary suggests that it's along the lines of PSoC5, which John has often described here (in CPLD/FPGA threads) as being a microcontroller SoC with partially documented programmable logic features.

 

That makes this board rather eclectic and somewhat alienating to those who prefer traditional CPU software programming.  Perhaps the manufacturer is trying to dispell that image by releasing the board at prices that fall below the worry radar ... except in NZ, that is.

PSoC4 is a low-cost version of PSoC5, replacing PSoC5's Cortex-M3 with a Cortex-M0.   The PSoC line is quite interesting: Cypress integrates a processor, various digital blocks, and analog blocks all onto the same chip with a programmable interconnect to tie everything together and route to the pins.  The idea is to have a single chip provide everything for an embedded product, including the analog circuits.  The functions of the blocks and the routing are all programmed by the CPU through addressable registers, almost all of which are documented.  Cypress has a Windows-based tool called PSoC Creator that lets you select and interconnect the blocks, and it generates a C program that does the register initializations for you so you don't have to read an 1800-page manual.

My beef with the chip has been that I want to be able to use it for teaching logic design using my own tools.  Cypress almost provides enough data to do this, but as far as I can tell the routing control registers aren't documented well enough to use them.  It may be that I'm wrong and the information is now there -- please tell me if that's the case!

PSoC has had limited success, largely because the chips have been rather expensive.  PSoC4 is supposed to change this by providing a highly capable SoC for US$1.

John Beetem wrote:

 

PSoC has had limited success, largely because the chips have been rather expensive.  PSoC4 is supposed to change this by providing a highly capable SoC for US$1.

Did you notice that the  CY8CKIT-042 PSoC4 Pioneer Kit board contains, in addition to the PSoC4 target device, a PSoC5 device that's used for board programming and debug?  (The intro video mentioned it.)  If PSoC4 is the cheap device, you'd think they'd use a second PSoC4 to provide that function on this cheap board.

It seems a little bizarre, but I guess they already had PSoC5 code developed for the required function, and don't expect to sell enough boards to recoup additional development required to use the cheaper part instead.

Morgaine Dinova wrote:

 

John Beetem wrote:

 

PSoC has had limited success, largely because the chips have been rather expensive.  PSoC4 is supposed to change this by providing a highly capable SoC for US$1.

 

Did you notice that the  CY8CKIT-042 PSoC4 Pioneer Kit board contains, in addition to the PSoC4 target device, a PSoC5 device that's used for board programming and debug?  (The intro video mentioned it.)  If PSoC4 is the cheap device, you'd think they'd use a second PSoC4 to provide that function on this cheap board.

 

It seems a little bizarre, but I guess they already had PSoC5 code developed for the required function, and don't expect to sell enough boards to recoup additional development required to use the cheaper part instead.

Yes, I saw that.  It's not at all unusual to have a much more capable part as the program/debug interface.  If I've read the data sheets correctly, the PSoC4 only has 32KB flash and 4KB SRAM, while the PSoC5 has 256KB flash and 64KB SRAM.  It's hard to squeeze much into 32K+4KB, particularly if the code is written by people who didn't grow up carrying around boxes of punched cards (2000 cards per box * one box per arm * two arms per human = 4000 lines of code that you can "comfortably" carry around if you have two arms).

Reminds me of an LPXpresso board I have for the LPC1114FBD48/301,1LPC1114FBD48/301,1 -- a Cortex-M0 with 32KB flash and 4-8 KB RAM.  It's controlled by an LPC3154 -- an ARM9 with 192KB RAM.  I don't know how this compares to an mbed because my mbed has the controller's part number erased.

It's often the case that the control SoC is the one to play with, provided that the vendor hasn't disabled access.

John Beetem wrote:

 

Reminds me of an LPXpresso board I have for the LPC1114FBD48/301,1LPC1114FBD48/301,1 -- a Cortex-M0 with 32KB flash and 4-8 KB RAM.  It's controlled by an LPC3154 -- an ARM9 with 192KB RAM.

Haha.  That's a pretty severe case of an application processor in servitude to a microcontroller.  It can't be impressed.

I guess it's only a matter of time before Cortex-A series devices are given such roles too, particularly if a small realtime microcontroller needs a full-function IPv6 stack and comprehensive networking apps, and the simplest way of providing this is by giving it an entire Linux subsystem on a different SoC.

Morgaine Dinova wrote:

 

I guess it's only a matter of time before Cortex-A series devices are given such roles too, particularly if a small realtime microcontroller needs a full-function IPv6 stack and comprehensive networking apps, and the simplest way of providing this is by giving it an entire Linux subsystem on a different SoC.

Actually, at some point it might be a good idea just to have the vendor's eval board be a BeagleBone cape.  That way they don't have to design their own controller hardware.  One problem with this is that the vendor has to worry about whether the user has a compatible operating system.  I don't have experience with Linux device drivers, but it may also be that it's a lot easier to write the whole debug controller on a bare chip than to write the Linux driver   Note that I didn't mention RasPi -- the vendor needs an open hardware project so it's not stuck if the controller board is discontinued.

John Beetem wrote:

Note that I didn't mention RasPi -- the vendor needs an open hardware project so it's not stuck if the controller board is discontinued.

How is any ARM SOC with a proprietary GPU considered to be open hardware ? Isn't that a contradiction of terms ?