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Embedded Linux Hardware Resources?
jessecurry asks: "I've recently come up with a conceptual Linux based piece of hardware and have been able to find a huge amount of information regarding getting Linux on to a device, but almost nothing about creating the device itself. I'd like to know if there are any books, online guides, or software that would help in designing a device that would accept some flavor of Linux. I really don't want to go 'off the shelf', but I need something that can at least display graphics, respond to positional input, and play sound. Also, is there a good place to have all of these components put together once I have a finalized design?"
On how many you want! The answer is very different even for 1 or 20, let alone two million.
The RTAI mailing lists are a good place for this kind of question however, and handhelds.org has a lot of links to embedded Linux projects.
Beep beep.
Some folks swear by 'em, some folks hate 'em. Check out http://www.oreilly.com/catalog/dbhardware2/ Covers a range of embedded devices from PICs to DSPs and talks about the various buses you'll see.
Why do you want to build it yourself?
While Linux runs on ARMs, be assured that building such a thing is not much different from designing a mainboard with bridges... yourself.
That's why I'm asking why.
- either you want to make it for fun, for learning. that's fine, go ahead
- or you have your idea about some software running on embedded Linux which you want to make into money. Then don't waste your time creating new hardware. Two links for you: <a href="http://www.pcengines.ch/wrap.htm">PCEngines WRAP</a>, <a href="http://www.soekris.com/">Soekris</a>.
Linux is an Operating System - it has drivers for *existing* hardware. It is really hard to write drivers (or modules in Linux-speak) for dealing with non-existing hardware - I see real problems with testing it. :)
So obviously if you plan to build hardware that will run Linux you need to use existing chips that have support in Linux. On the other way you may be willing (but there is no economical point for you really) to design some brand new hardware - just make sure it is atractive so few linux-heads-devs will use it and also make sure you release full specification of it.
Get a reference board from one of the chip vendors. You'll find that they've generally already built a board that does anything you want to do and more. Then you can strip the features you don't want, and the design work is essentially done.
In my experience, Cirrus Logic is very Linux friendly, with good driver support for their ARM processors and dev boards.
I'd take a wild guess that greater than 90% of Linux embedded systems use some kind of ARM processor. Since that design has been licensed far and wide, you can probably find a customized one with just the peripherals you are looking for, from some company or other (e.g. Phillips, Atmel, Freescale, etc. etc. - just search digikey or mouser for some ideas). It uses a 32-bit instruction set (good for Linux, and good for porting code in general), typically has an LCD driver on the chip, and you might even be able to find one with a DAC. For high-quality audio output, you can use a Wolfson DAC (again there are many choices depending on whether you need a headphone amp, ADC, line-in, mic pre-amp, mixer, how many channels etc.) The ipods tend to use these chips (the 2-channel kind with a headphone amp) so some of them are really cheap because of the economies of scale. For even better quality, the best is probably Burr-Brown (as used in the SlimDevices Squeezebox).
As another poster suggested, you can do prototyping with a Gumstix. Just the display may be a pain with those because they use that teeny-weeny surface-mount Hosiden connector for most of the I/O lines, and you will probably need to build your own display adapter board. But they do have an audio daughterboard already. For something more expensive but a little more ready-to-go (as a prototype), check out the offerings from Arcom; I've used those as well. Or look for some other SBC (linuxdevices.com is a good place to search). You can develop software that way, make sure you know how to use all the hardware you're going to need, and in parallel be working on your final board design (suitably miniaturized if necessary, all on one board, and leaving off the features that you don't need).