presence
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Re: BCM2835 Questions

Thu Jan 05, 2012 3:06 am

I have some questions about the BCM2835 processor on the raspberry pi.  I understand its an ARM 11 core, but I haven't seen many other details.

1) Where can I order small quantities of the processors for prototyping?

2) Does the BCM2835 include the Trustzone functionality that you normally see with the ARM 11 series?

3) Is there a pinout somewhere that I can grab and review?  I haven't found one.

4) I'm assuming its BGA, is there a BGA socket I can buy?

Thanks for your help.

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Chromatix
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Re: BCM2835 Questions

Thu Jan 05, 2012 3:42 am

Let's answer your last question first.

It's BGA.  There are no sockets for BGA.  You cannot hand-solder (or hand-unsolder) BGA.  You need an advanced manufacturing facility to make anything using BGA.

Knowing that, are you still interested in having the other questions answered, or will you just buy an R-Pi since the hard work has then been done for you?
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error404
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Re: BCM2835 Questions

Thu Jan 05, 2012 4:35 am

1) You can't, and probably won't ever be able to, unless of course you have an existing relationship with Broadcom.

2) Dunno.

3) Maybe at some point, but as yet, no.

4) Yes, but if you have to ask, you don't want to know the price. It probably has at least 2 more digits in it than you were expecting.

BGA can be done at home with care, but you will need a paste stencil, high-quality PCB and some practice. This is probably also a 0.5mm pitch part I would guess, so that may not even be particularly viable.

If you're at the point where you're designing your own board, you may as well go with an SoC that's more available and better documented.

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Jessie
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Re: BCM2835 Questions

Thu Jan 05, 2012 5:05 am

presence said:


I have some questions about the BCM2835 processor on the raspberry pi.  I understand its an ARM 11 core, but I haven't seen many other details.

1) Where can I order small quantities of the processors for prototyping?

2) Does the BCM2835 include the Trustzone functionality that you normally see with the ARM 11 series?

3) Is there a pinout somewhere that I can grab and review?  I haven't found one.

4) I'm assuming its BGA, is there a BGA socket I can buy?

Thanks for your help.



I had very simular questions when I started on this forum so here are the answers.  You can't order small quantites of this chip, Broadcom dosn't operate like TI, ST Micro or Atmel.  These chips were designed to be placed into cell phones by OEMs.  There is no pinout and unless Broadcom cuts this foundation a deal to allow it you will likely never see one.  As stated in the above post a BGA socket is costly, it's not like intel's BGA Core series where intel worked with foxconn to get a affordable BGA socket out the door.  No one other than manufacturers need a BGA socket for a processor this size so they cost a lot of money, ie no one is upgrading cell phone and Roku processors they generally just replace the whole device.

presence
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Re: BCM2835 Questions

Thu Jan 05, 2012 5:11 am

"Knowing that, are you still interested in having the other questions answered, or will you just buy an R-Pi since the hard work has then been done for you?"

Regardless of the answers to the questions, I am buying a Pi (or two) anyway, assuming I get notification before they sell out.

I guess I need to look at someone elses ARM 11 core based processor...Unfortunately TI's OMAPs are also in the same category as far as availability goes.  Quite frustrating.  Ultimately, it doesn't have to be an ARM 11, I just ultimately want a ARM core with trustzone included.

Truly strange.

ArgentsQuest
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Re: BCM2835 Questions

Thu Jan 05, 2012 7:33 am

The Wiki site shows that the BCM2835 has an ARM11 ARM1176JZF-S core.  This core includes Trusted Zone and the technical reference manual can be downloaded from the ARM website.

jamesh
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Re: BCM2835 Questions

Thu Jan 05, 2012 7:52 am

presence said:


"Knowing that, are you still interested in having the other questions answered, or will you just buy an R-Pi since the hard work has then been done for you?"

Regardless of the answers to the questions, I am buying a Pi (or two) anyway, assuming I get notification before they sell out.

I guess I need to look at someone elses ARM 11 core based processor...Unfortunately TI's OMAPs are also in the same category as far as availability goes.  Quite frustrating.  Ultimately, it doesn't have to be an ARM 11, I just ultimately want a ARM core with trustzone included.

Truly strange.


What is truly strange?

The chip is about 0.2mm pitch I think, I'll post a picture when I have time. You can buy BGA sockets for it - I think they are over > $1000USD each and very large (larger than the Pi board). So not particularly attractive pricing!
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Re: BCM2835 Questions

Thu Jan 05, 2012 6:12 pm

Presence, you will need to contact Broadcom directly about pricing, prototypes, pinout and the other information you would need to design and build a device based on the BCM2835.

This is exactly the same as for any embedded CPU, or even microcontroller.
- Even for the PIC you need to get the information from Microchip.

Finally, in the embedded CPU space, no chip manufacturers and very few resellers bother with sub 10,000 unit orders.

- Microcontrollers are somewhat different, being a lot simpler and cheaper.

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Re: BCM2835 Questions

Thu Jan 05, 2012 7:35 pm

I did a quick search at Digi-Key and you can buy TI OMAP and Freescale MX31 in single units: they cost about as much as a RasPi

I used 50 mil pitch BGA sockets once in a project, figuring it would help if there were any errors.  It turned out to be a terrible idea.  The contract manufacturer could not reliably solder the BGA socket onto the PC board, and I wasted a lot of time trying to get the BGA to work.  I wouldn't ever use BGA sockets again -- now I'm just very careful to get the pinout right and I bring unused pins out to test holes just in case.

presence
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Re: BCM2835 Questions

Thu Jan 05, 2012 7:38 pm

My goals:

Processor with trusted processing module

Small number of pins (less than 208 PLEASE!)

documentation for what pin is for what

Thats why Im aiming at ARM.

I don't mind if they are $20-$50.  BGA is something I prefer to not have to deal with.  Socketed option would be big benefit.

Kevin

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Re: BCM2835 Questions

Thu Jan 05, 2012 8:07 pm

presence said:


My goals:

Processor with trusted processing module

Small number of pins (less than 208 PLEASE!)

documentation for what pin is for what

Thats why Im aiming at ARM.

I don't mind if they are $20-$50.  BGA is something I prefer to not have to deal with.  Socketed option would be big benefit.

Kevin


I'm not aware of many non-BGA Arm chips. Doesn't sound like this SoC is for you, unless you want to sell many tens of thousands. Fine pitch BGA, lots of balls, and no docs from Broadcom without NDA and big sales.
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presence
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Re: BCM2835 Questions

Thu Jan 05, 2012 8:12 pm

All I have seen in the ARM11 family are BGA.  You are absolutely correct that this specific SoC is not for me, so I have moved back my target to other ARM processors with TrustZone capability.  I have seen QFP from NXP and TQFP and LQFP for older series Arms, so I need to push that way I believe.  I just need to collect those requirements and see what falls out.

presence
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Re: BCM2835 Questions

Thu Jan 05, 2012 9:13 pm

Just as an aside, I have seen many conversations stating that trustzone is often disabled (and some level of hearsay states this is the case with the TI OMAP processors that are "loose") by the manufacturer.

How sad.

Benedict White
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Re: BCM2835 Questions

Thu Jan 05, 2012 11:14 pm

presence said:


Just as an aside, I have seen many conversations stating that trustzone is often disabled (and some level of hearsay states this is the case with the TI OMAP processors that are "loose") by the manufacturer.


What is the trustzone thing about?

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Re: BCM2835 Questions

Thu Jan 05, 2012 11:58 pm

It is the security system which surrounds the ARM and everything connected to the ARM. I am not impressed with the ARM trustzone. Security was not embedded in the ARM from the beginning. What I have seen looks like some blocks have been thrown in as an afterthought and connected up with sellotape and chewing gum. It may work but it is not integrated.

Benedict White
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Re: BCM2835 Questions

Fri Jan 06, 2012 12:15 am

Gert said:


It is the security system which surrounds the ARM and everything connected to the ARM. I am not impressed with the ARM trustzone. Security was not embedded in the ARM from the beginning. What I have seen looks like some blocks have been thrown in as an afterthought and connected up with sellotape and chewing gum. It may work but it is not integrated.


Quite an impressive achievement on a small piece of silica though!

So it is supposed to do what? Prevent untrusted code running? If so, how is a transistor supposed to work out that?

presence
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Re: BCM2835 Questions

Fri Jan 06, 2012 1:04 am

It provides mechanisms to allow only signed code execution, DRM features, signature based transactions, and otherwise.  Its not all bad, unless its done with the wrong intent.

Benedict White
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Re: BCM2835 Questions

Fri Jan 06, 2012 1:10 am

presence said:


It provides mechanisms to allow only signed code execution, DRM features, signature based transactions, and otherwise.  Its not all bad, unless its done with the wrong intent.


Ah I see, so as an open source fan I would detest it? Cool!

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Re: BCM2835 Questions

Fri Jan 06, 2012 8:53 am

Benedict White said:


presence said:


It provides mechanisms to allow only signed code execution, DRM features, signature based transactions, and otherwise.  Its not all bad, unless its done with the wrong intent.


Ah I see, so as an open source fan I would detest it? Cool!


Well, not if it were your credit card details it was protecting.....
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Re: BCM2835 Questions

Fri Jan 06, 2012 12:41 pm

Chromatix said:


You cannot hand-solder (or hand-unsolder) BGA.  You need an advanced manufacturing facility to make anything using BGA.


I wouldn't be so sure if I ware you. There are many ways to solder BGA. For example this:


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Re: BCM2835 Questions

Fri Jan 06, 2012 1:06 pm

Not sure you could do that on this...

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Neil
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Re: BCM2835 Questions

Fri Jan 06, 2012 1:22 pm

I think JamesH has just given you the finger!

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piglet
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Re: BCM2835 Questions

Fri Jan 06, 2012 1:36 pm

All you'd need is a handful of Lilliputians with itty bitty soldering irons. Easy.

Hugh Reynolds
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Re: BCM2835 Questions

Fri Jan 06, 2012 2:24 pm

prezek said:


I wouldn"t be so sure if I ware you. There are many ways to solder BGA. For example this:




presence
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Re: BCM2835 Questions

Fri Jan 06, 2012 2:25 pm

James, have you looked at that through a mirror?  It looks like it says something.

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