Minimum configuration to run embedded Linux on an ARM processor?

Question

I need to produce an embedded ARM design that has requirements to do many things that embedded Linux would do. However the design is cost sensitive and does not need huge amounts of horse power. Mostly will be talking to serial interfaces. Ideally I would like to use one of the low end ARMs. What is the lowest configuration of an ARM that you have successfully used embedded Linux on.

Edit:

The application needs a file system on some kind of flash device and the ability to run applications for processing the data. Some of the applications might be written by others than myself. I also need to ability to load new applications or update old apps using the serial ports to accept the apps.

When I have looked at other embedded OSes they seem to be more of a real time threading solution than having the ability to run applications. I am open to what ever will get the job done.

Answer 1

I've had success even on ARM7TDMI, so I don't think you're going to have any trouble. If you have a low-requirements system, you could use any kind of lightweight real-time executive and have a lot better experience than you would getting Linux to work.

Answer 2

I've used a TS-7200 for about five years to run a web server and mail server, using Debian GNU Linux. It is 200 MHz and has 32 MB of RAM, and is quite adequate for these tasks. It has serial port built in. It's based on a ARM920T.

This would be overkill for your job; I mention it so you have another data point.

Answer 3

ucLinux is designed specifically for resource constrained targets, but perhaps more importantly for targets without an MMU.

However you have to have a good reason to use Linux on such a system rather than a small real-time executive. Out-of-the-box networking, readily available drivers and protocol stacks for complex hardware and support for existing POSIX legacy or open source code are a few perhaps. However if you don't need that, Linux is still large, and you may be squandering resources for no real benefit. In most cases you will still need off-chip SDRAM and Flash if you choose Linux of any flavour.

I would not regard serial I/O as 'complex hardware', so unless you are running a complex, but standard protocol, your brief description does not appear to warrant the use of Linux IMO

Answer 4

For several years I've been using a gumstix to do prototyping and testing and I've had good results with it. I don't know if the processor they are using (Intel PXA255 on my board) is considered low-cost, but the entire Verdex line seems pretty cheap to me for an adaptable device.

Answer 5

I think you need to weigh your cost options here.

ARM + linux is an option but you will be paying a very high operating overhead for such a simple (from your description) set of features. You can't just look at the cost of the ARM chip but must also consider external RAM which will very likely be required as well as flash to get enough space available to run the kernel + apps.

NOTE: you may be able to avoid the external requirements with a very minimal kernel and simple apps combined with a uC with large internal resources.

A second option is a much simpler microcontroller with a light weight OS. This will cut your hardware costs on the CPU and you can likely run something like this without external RAM or flash (dependent on application RAM and program space requirement)

third option: I don't actually see anything in your requirements that demands any OS at all be used. Basic file systems are very simple, for instance there are even FAT drivers out there for 8 bit PIC's. Interfacing to an SD card only requires a SPI port and minimal external circuitry.

The application bit could be simple or complex. I've built systems around PIC18 microcontollers that run a web server and allow program updates via a simple upload screen, it just stores the new program into an EEPROM or flash, reboots into a bootloader and copies the new program into internal program memory. You could likely design a way to do this without the reboot via a cooperative multitasking type of architecture. Any way you go the programmers writing the apps are going to need to have knowledge of the architecture and access to libraries / driver you write. Your best bet to simplify this is to provide as simple an API as possible and to try to automate the build process for them.

The third option will be the "cheapest" in terms of hardware as there will be very little overhead in the processing of your applications allowing you to get away with minimal processing power and memory. It likely will require some more programming/software architecting on your part but won't require nearly the research you will need to undertake to get linux up and running in addition to learning to write the needed device drivers under a linux paradigm.

As always you have to include the software development costs in the build cost of the device. If you plan to build 10,000+ of these your likely better off keeping hardware costs down and putting more man power into designing a software solution that allows that hardware to meet the design goals. If your building 10 of them, your better off spending an extra $15-20 on hardware if it can cut down on your software development costs. For example an ARM with MMU with full linux kernel support and available device drivers.

I kind of feel that your selecting the worst of both worlds at the moment, your paying extra to get a uC you can run linux on but by doing so your also selecting a part that will likely be the most complex to get linux up and running on, especially having not worked with linux on embedded platforms before.

Answer 6

My DLINK DIR-320 router runs Linux inside.

And I know some handymen, flashing it with Optware and connecting USB-hub, HDDs, USB-flash, and much more.

It's low-cost ready for use "platform". (If you don't need mass production). But maybe more powerful than you need.

Additionally, it can be configured wirelessly via web-interface even through your pda :)

Answer 7

tray to use the load img for hd, assuming that you dont have cd/dvd/usb media, and just the serial port, by serial try to use the way to transfer through serial and load the installer from img hd to install and use the same disk for it. if this is not the idea then i need to know more about ,and then may i'll be agree with all the last comments, and may is better to think about the first advise.