[Discuss] Raspberry Pi

[chris at tylers.info (Chris Tyler)]

On Thu, 2012-06-28 at 14:30 -0400, Tom Metro wrote:
> 
> > Is it worth picking up?
> 
> All depends on what you plan to do with it. Lots of talk of it being
> used as a media playback device, and it being able to run XBMC, but I
> think anyone using it as a home theater PC is going to be disappointed
> by the performance (based on reviews I've read; see 3rd link above).

It's interesting to look at the SOC in the Raspi -- it's actually a GPU
(with decent general-purpose code execution capabilities) specifically
designed for a streaming media player (there's a name-brand unit you can
get at Best Buy based on this chip). The ARM core was added when Eben
Upton realized that the chip package was 0.75 mm2 larger than the chip
he was working on, and he threw in an ARM11, the largest that would fit.
So you have a pretty rocking GPU paired with a fairly tiny ARM core.

> It's not ideal for embedded applications where you want lots of I/O,
> unless you are prepared to build your own peripheral board. (There is an
> "all-in-one" peripheral board soon to be available, but I suspect it
> will cost as much as the Pi, and likely several times more. For now, at
> least, it doesn't have an ecosystem of available peripherals like the
> Arduino has.)

It looks like there are a ton of Raspi expansion boards set to ship over
the next few months, including Aduino shield adapters -- but there's a
pretty good amount of GPIO directly available on the Pi and it's really,
really trivial to hack up your own interfaces. You can wire up an LED
and get it blinking in under a minute :-)

So this stuff works really well on the Pi:
- H.264 video decode at up to 1080p
- OpenGL-ES 2.0 graphics
- GPIO/SPI/I2C device control (think Arduino with two orders of
magnitude more processing capability - e.g., robotics with OpenCV etc)

This doesn't work well on the Pi:
- 2D graphics (fbdev) - this may improve if/when we get the GPU into the
X11 (or Wayland?) path but I'm not holding my breath
- memory-intensive apps (coupled with above, this rules out a lot of GUI
scenarios, especially since users see a big 1080p display space and want
to open lots of windows)
- device control which requires analog or PWM I/O - additional logic
required

It looks like there will be a *ton* of <$100 ARM boards showing up over
the next while, with very different specs and connectivity. For example,
the VIA APC board (apc.io) will be one of the next -- $49, about the
same CPU as the Raspi (800 MHz ARM11), more RAM (512M), lower-end video
(720p, unsure about decoding/OpenGL capabilities), VGA out, lots of USB
ports, audio input as well as output. But this board doesn't have any
accessible GPIO, and VIA says they only have the resources to support
Android on it -- so it's probably a bit better for desktop use,
questionable for learning programming, and not really good for
interfacing to things.

-Chris