[ECOS] Does 256kByte flash and 64kByte RAM + TCP/IP make sense for eCos?

Andrew Lunn andrew@lunn.ch
Fri Jun 13 10:25:00 GMT 2008


> It seems like the amount of flash + ram available inside a
> microcontroller has been stuck at or below 256kBytes and 64kByte RAM
> the last 5 years.

Im guessing this has to do with the silicon processes being used, but
im no expert in this area. 

> However, eCos is not in the game if flash/ram is stuck at 256kBytes/64kBytes
> respectively.

The AT91SAM7X256 has exactly this combination. There is also a
AT91SAM7X512 with double the flash.

I know of people who have used these devices with eCos, including the
company i work for. With careful tuning, LwIP can be used. RAM is more
of an issues than FLASH, so you need to design your system with
limited number of threads since stacks are expensive, avoid putting
big objects on the stack and tune your stacks etc. Use the const
keyword where ever possible so that it stays in the rodata segment
which stays in flash etc.

eCos is usable on such systems, but requires a bit more thought and
design work to live with the RAM restrictions.

     Andrew

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