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Forum: ARM programming with GCC/GNU tools Programming At91SAM7x256


Author: Akrmi Yaacoub (Company: eniso) (oresama)
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Hi everyone, I'm new here

I want to know if it's possible to program At91SAM7x256 without need to 
use a JTAG connector and cable.

Thanks

Author: Andreas Schwarz (andreas) (Admin) Flattr this
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You can program it over USB with the SAM-BA bootloader. See 
http://www.atmel.com/dyn/products/tools_card.asp?t... for more 
information.

Author: Akrmi Yaacoub (Company: eniso) (oresama)
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thank you for help
I want to ask if it's a good practice to port linux on this MCU

Author: Clifford Slocombe (clifford)
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Akrmi Yaacoub wrote:
> I want to ask if it's a good practice to port linux on this MCU

It is an ARM7 part so has no MMU.  There are distributions of Linux that 
will run without an MMU (uClinux for example), but just because you can, 
does not mean you would want to.  Lack of memory protection removes one 
major advantage of using Linux.

Also no usable Linux distribution will run in the on-chip memory 
resources; you'll need a board with external RAM and unless you boot 
from removable media, external Flash too.

If you need hard real-time performance and small memory footprint, Linux 
would not be appropriate.  If you want to take advantage of 
communications devices and storage media of various types Linux may be a 
good choice.

Consider something more suited to small devices such as eCos if you need 
real-time and extensive device support, or FreeRTOS is you simply need a 
real-time preemptive priority based scheduler.

Clifford

Author: Andreas Schwarz (andreas) (Admin) Flattr this
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I agree, this is not the kind of controller that you would run Linux on. 
If you are interested in playing with Linux on an ARM controller, use 
one of the bigger ARM9 parts with a MMU, like the SAM9 series. But in 
any case you will need external Flash and RAM and a whole lot of 
infrastructure, so it's best to start with a board that already comes 
with a working Linux distribution, otherwise you may be soon get 
frustrated.

Author: Akrmi Yaacoub (Company: eniso) (oresama)
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My application needs an I/O (LCD, SD, GSM via rs232) management with a 
soft real time performance and not a lot of data to store on memory.


I know that it's not necessary to make it with embedded linux kernel
But I want to do so to familiarise with embedded linux.

Do you advise me to switch to an ARM9 MCU if so can you, please, 
recommand me a low cost board that have these features?

Kind regards

Author: Clifford Slocombe (clifford)
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How much is "low cost"?  To run Linux sensibly you need probably an ARM9 
at 200MHz with >=16Mb external RAM and >=4Mb of Flash.  That is just teh 
requirement to get the OS to run.  Linux is a general purpose OS, if 
your application is very specific and small, you will be spending more 
on hardware to support the OS than is strictly necessary to implement 
the application.

I suggest then that you simple Google "ARM9 development board" if you 
still think you need this.  I think eCOS may be more appropriate 
however.

Author: oresama (Guest)
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Ok thank you, I got it ecos or freertos are the more suitable for my 
application.

and what about distributions like RTLinux can it run inside an MCU with 
an MPU but not MMU?

Oresama

Author: Clifford Slocombe (clifford)
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oresama wrote:

> and what about distributions like RTLinux can it run inside an MCU with
> an MPU but not MMU?
>
You are really stuck on this Linux thing aren't you!?  That is a 
question probably best answered by checking out the project's own web 
site.

RTLinux however has even more complex requirements that regular Linux. 
Despite its name it is not in fact a Linux distribution, it is a VM that 
runs a real-time micro-kernel with Linux as a virtualised guest OS.  So 
not a chance on an ARM7 IMO.

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