josheeg
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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Tue Apr 03, 2012 5:09 pm

Hi were can the broadcom chip in the rasberry pi be bought where can that chips datasheet be found?

I read the linux magazine article on it. Also the ted talks on the connectome and the ted talks on the ibm blue brain project. Also read some about linux clustering and clustering GPUs.

BCM2835 is the chip mentioned in the wikipedia. I am interested in this for a kicad open design project.

16000 cpus are in the ibm blue brain that recreates a neocortical column 1000 artifical neurons per processor. Could robot assembled pannels of BCM2835 s be used to simulate 1000 artifical neurons eatch then the pannels could be stacked to create something similar.

I wanted to use all open source technology kicad freeroute data sheets and documentation I can find on the artifical neurons topology and structure that makes them.

well email me at [edit: not a good idea to post your email - too much spam:  use PM instead]


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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Tue Apr 03, 2012 6:24 pm

Broadcom is a very closed company, they basically won't sell you anything or give you acess to their data unless you come to them with a buisness plan that they think makes you worth dealing with. The Pi guys only got in the door because they have people who work there.

They have released an abbridged datasheet discribing some of the arm perhipherals for the benefit of Pi users but it's nowhere near enough to design your own system based round the chip.

Some of the other arm SOC vendors are a bit more open but you still won't get any real info on GPU internals without convincing them you are important/trustworth enough and then signing a NDA.

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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Tue Apr 03, 2012 9:10 pm

Actually, you could design a system around just the Arm datasheet, if you just want to use the Arm (and basic framebuffer). However, the OP's task would require the GPU for real horsepower, which, without openCL or similar, is not accessible for general purpose compute.

We have discussed this sort of thing at work. I reckon the low power requirement of the VC4 GPU and its high compute power would make it a good subject for this sort of supercomputing work but for one issue -  Comms - you really need dedicated comms channels between devices for a supercomputer, which the chip doesn't have.
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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Tue Apr 03, 2012 9:41 pm

JamesH said:


Actually, you could design a system around just the Arm datasheet, if you just want to use the Arm (and basic framebuffer).


I don't see any information in the "arm perhiperals" datasheet about pin layout (pin numbers are given for some things but not crucial things like power and ground) or physical dimensions, or power arrangements (I understand the chip has a built in switched mode regulator) or board layout reccomendations or memory types or all of the loads of other things you have to consider when designing with a chip like this.

Note: This is NOT a criticism of those who put that datasheet together. I'm just saying it was clearly neither intended for nor suitable for those designing thier own boards around the chip.


However, the OP's task would require the GPU for real horsepower, which, without openCL or similar, is not accessible for general purpose compute.


Indeed.


We have discussed this sort of thing at work. I reckon the low power requirement of the VC4 GPU and its high compute power would make it a good subject for this sort of supercomputing work but for one issue -  Comms - you really need dedicated comms channels between devices for a supercomputer, which the chip doesn't have.


I wonder if the camera and display interfaces could be re-purposed as an inter-chip communication system.


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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Wed Apr 04, 2012 7:29 am

hzrnbgy said:


The datasheet is nowhere near a real datasheet...


In fact it is the Broadcom datasheet with unnecessary or proprietary stuff taken out....

The reason the datasheet is not suitable for designing your own board around the chip, is that you cannot buy the chip! This makes all the pin out data etc completely unnecessary. However it should be sufficient to take an existing Raspi and write your own OS for example (without graphics acceleration). So for the purposes of the foundation it's spot on.
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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Wed Apr 04, 2012 3:05 pm

So what your saying is the chip is unavalable so a open design is not realy helpful unless I somehow licenced with broadcom possibly bought a lot of chips and then would get their datasheets and not be able to have a open design but If linux could be clustered by ethernet or the GPIO pins of the gurtboard mentioned in the linux magazine article that would be my only route.

Does anyone know if their are arm 11 and possible GPU s that are acsessable from digikey and mouser?

Would be able to load the same sd card?

Also this was for repurposing the broadcoms chip as a open design cluster to allow for clustered computer pannels that then could be stacked.

Discover magazine and the mind is very interesting this month. Check it out more stuff on connectomes IBM Blue brain and stuff.

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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Wed Apr 04, 2012 8:32 pm

Basically, you first paragraph is correct. If you buy a lot of chips (hundreds of thousands), you will get datasheets and tech support (you really do need both for chips this complex when designing in from scratch).

This is the case, I think, for most if not all SoCs of similar type out there.

The SD card image is specific to the Raspi.

This particular chips isn't really suitable for real work use cases of cluster computers - the lack of access to the GPU functionality, and the relatively slow Arm chip means there are better options.
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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Wed Apr 04, 2012 8:41 pm

hzrnbgy said:


The datasheet is nowhere near a real datasheet...



It is NOT a datasheet. The title also says it is not a data sheet. It clearly states that it is a description of how to access peripherals from the ARM. Nothing more.

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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Wed Apr 04, 2012 9:45 pm

Gert said:


... it is a description of how to access peripherals from the ARM. Nothing more.


JamesH said:


However it should be sufficient to take an existing Raspi and write your own OS for example (without graphics acceleration). So for the purposes of the foundation it's spot on.


Coupled with Gert's software from his latest hardware revision it does it for me for peripheral access but if we do have fanciful ideas about rolling our own OS, how do we display stuff even at text level and get to the USB for keyboard?

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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Thu Apr 05, 2012 7:00 am

The framebuffer is memory addressable  from the Arm I think - that's how the Linux FB stuff works I believe. So in that way it very similar to the BBC micro....

Not sure of where in memory it is though, buit I am sure that information is available somewhere.

No idea about USB though.
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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Thu Apr 05, 2012 7:44 am

The "where in memory" is in the datasheet for most things. I didn't happen to see it for the framebuffer, but then again I didn't look for it. On the other hand, Linux knows and you have the source. So that information is available.

Farnell offered "raspberry pi chipset" for sale on the 29th of february. If that product comes back, you might be able to buy small quantities of BCM2835's from farnell in the future....
Check out our raspberry pi addons: https://www.bitwizard.nl/shop/

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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Thu Apr 05, 2012 8:03 am

I am still hoping to see a full schematic of the RaspPi, although it seems the Foundation might not consider that necessary unless the CPU chip is opened.

It was very empowering to have the BBC Micro schematic, even if you intended to do nothing with it, but there was stuff you could do, stuff Acorn had never even considered. Look at the Sideways ROM expansion boards for example, or the Computer Concepts speach ROM.

Even if all we got was a list of components and a description of the test-points, it would still save many RaspPis from ending up in the dustbin when something got zapped or chewed.

But at the very least we need a full power schematic, (and no, Liz did not post one; it does not include the polyswitches or the USB and expansion ports.)

josheeg
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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Thu Apr 05, 2012 5:33 pm

So I should look at something like the beagle bone since looking for a arm 11 and gpu would be a lot of work. The documentation and chips are avalable also.

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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Thu Apr 05, 2012 6:43 pm

There is no hard frame buffer. I read somewhere that you send a message to the GPU telling it the start address+ height and width. This information has been shared with all the early developers so I assume the GPU message interface description is somewhere defined. (Don't ask me where, I have mostly hardware knowledge )

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Re: I searched for the Rasberry Pi's broadcom chip in digikey mouser and broadcom where is its datasheet? Where can it be purchased?

Thu Apr 05, 2012 6:51 pm

josheeg said:


So I should look at something like the beagle bone since looking for a arm 11 and gpu would be a lot of work. The documentation and chips are avalable also.


go with this. a lot better to start with when learning how to program embedded systems. the LPC1769 datasheet is readily available in its full glory.

http://iteadstudio.com/store/i.....cts_id=539

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