

Raspberry Pi Model B Schematics - stevenrossuk
http://www.raspberrypi.org/archives/1090

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zdw
Wow... 17 unattached GPIO pins off the CPU. I wonder if they just ran out of
room to put them on the board, or if they have lack alternate pin-specific
capabilities that the used pins have.

I kind of wish there was a harder to use card edge connector for these - they
could likely implement an additional 2 SD card slots or similar I/O.

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joezydeco
Man...two unused pins on the external LVDS display header. They could have
thrown an I2C pair on that and made it really easy to add an external
touchscreen or other kind of display device. Shame.

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rollypolly
This has to be one of the most hacker-friendly companies out there. Kudos!

~~~
A1kmm
It is worth noting that they are an educational charity, not a for-profit
organisation.

I think it is great that they have released this - and I think that Broadcom
also deserves credit for allowing them to release a schematic giving away the
pin-out of the BCM2835 SoC - it makes the Raspberry Pi so much more useful to
know what the outputs of the system are.

This opens up the possibility of trying to work out how to use the unused pins
on the BCM2835 based on the names. I haven't been able to work out what the HD
pin group does (probably not SATA or PATA based on the number of pins, and
HDMI has its own pin group). There seems to be a CAM0 not connected to
anything - given CAM1 seems to be a camera, it looks like it is for an
additional camera. It also has CCP2 outputs for a CCP2 camera. I also haven't
been able to work out what SLIM is - but given it has two pins, CLK and DAT, I
guess it is some kind of serial data protocol.

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A1kmm
Although they look like they are in the middle of the BGA ball array, and
probably on a pad that is just floating, so actually connecting anything to
the pins that the board isn't designed to allow access to is probably
effectively impossible.

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chj
is there anybody specialized in circuit design? i mean, how hard is it to
build a cheap Pi equivalent board? If this is so popular, why no commercial
version?

~~~
elliotanderson
The Pi has kicked off some interest in hardware hacking for myself too. My
question is how hard would it be to embed an 802.11 radio into the same board
for a discreet sensor project

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stephen_g
I haven't looked at the schematics yet, but generally a SoC based design like
this needs at least a six layer board, which combined with the speeds it runs
at is pretty advanced electronic design...

Coupled with that, it can be really hard to get low volumes of some of the
parts they use, like the SoC, PMIC (power management IC) and so on (although
you can get free samples if you ask sometimes - but they generally won't give
them to you unless there's a chance you'll put through a big order with them
in the future). And soldering the BGA parts onto the board would be a pain
unless you pay for it to be assembled for you...

Unless you know a lot about that sort of thing, it would probably be more
successful to design something that interfaces with a Pi.

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sveiss
My university had a wonderful pair of courses in the first year of its CS
degree. The first had us build a Z80-based computer on breadboards, with a
couple of hulking ancient HP logic analyzers to debug with. For the second,
they gave us an assembled Z80 single board computer and had us do something
interesting with it -- games displayed on an oscilloscope, control a small
robot, etc. For both courses compilers were strictly forbidden.

It was a great way of bridging the abstraction gap between the physical
hardware and the code we typed at the keyboard. (We were also required to take
courses in basic digital and analogue design and compiler construction to give
an overview the rest of the stack, too.)

Nowadays, I think they've switched to using ARM boards for the second course
in the build-a-computer series. From a hardware reliability and cost
perspective it makes sense, but it's a little sad that the "I built one like
this! Just not quite so neatly..." factor has been lost.

As a software guy, the details of the Pi's PCB layout are about as
impenetrable to me as the internals of the SoC itself are. It's Magic
Electronic Stuff!, but just a tad more powerful than the Z80 I used to play
with.

