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SPI DataFlash vs parallel Flash for running Linux on an ARM board

Started by Mayank Kaushik March 16, 2005
Hi,

Ive been developing a board based on the AT91rm9200 (arm920t). I have
added 16 MB ram to this board, and am looking to add some flash.

I want Linux installed on this board. (this is basically an educational
project)
My question is, do i HAVE to add a parallel flash? will such a system
be capable of running Linux if i just add an 8MB SPI dataflash?

As far as i know, a parallel flash is helpful only if one wants to boot
direclty off the flash, and not use the bootloader that may be burnt
into the controller`s on board ROM. Is this correct?

Another thing..how can i interact with the installed Linux? I heard
thar BusyBox provides some shell utilities..is it possible to write a
driver such that a shell prompt or something is displayed on a terminal
program running on a PC, thats connected to this board with a serial
link?

As i said, its an educational project, so "why dyu want to do this" has
no particular answer :-)
Please advise me, as im totally new to this.

Regards,
Mayank

In news:1110967848.066234.241660@g14g2000cwa.googlegroups.com,
Mayank Kaushik <prehistorictoad2k@yahoo.com> typed:

> Ive been developing a board based on the AT91rm9200 (arm920t). I have > added 16 MB ram to this board, and am looking to add some flash. > > I want Linux installed on this board. (this is basically an > educational project) > My question is, do i HAVE to add a parallel flash? will such a system > be capable of running Linux if i just add an 8MB SPI dataflash?
You don't have to use parallel flash. Your bootloader, loaded from dataflash into the internal RAM by the AT91RM9200 ROM, should then load the kernel image from some kind of flash to SDRAM and execute it. My board uses a small dataflash, and loads the kernel image from a NAND flash. Your bootloader could load the kernel image from other parts of a large dataflash.
> As far as i know, a parallel flash is helpful only if one wants to > boot direclty off the flash, and not use the bootloader that may be > burnt into the controller`s on board ROM. Is this correct?
Yes.
> Another thing..how can i interact with the installed Linux? I heard > thar BusyBox provides some shell utilities..is it possible to write a > driver such that a shell prompt or something is displayed on a > terminal program running on a PC, thats connected to this board with > a serial link?
The Linux kernel (with appropriate patches) already contains a driver for the AT91RM9200 serial ports, so this is already done. In addition to the raw kernel image, you need a root filesystem containing BusyBox and your programs. This root filesystem could be a RAM disk, loaded into RAM by your bootloader, or a real flash filesystem supported by Linux. My system uses the Yaffs filesystem on a NAND flash chip. Karl Olsen