[uClinux-dev] use RAM over SPI

[Erwin Authried]

Am Freitag, den 05.01.2007, 18:41 +0100 schrieb
stefan.ulbrich at stud.uni-karlsruhe.de:
> Hello list!
> 
> I want to create an embedded SBC capable of running ucLinux. I want to 
> use an arm7tmdi with 12-Bit AD/DACs from Analog devices. The second 
> requirement is the capability to drive a LCD screen.
> 
> As this arm7 mC has only 16 external adress lines I cannot adress 
> enough memory to run linux nor a LCD controller. But this spring a new 
> LCD controller from Epson is announced that can be adressed to via SPI 
> and contains a SDRam controller. An External RAM therefore can be 
> accessed through the SPI interface.
> 
> I'm a completely new to linux internals so my question is if it is 
> generally possible to tell linux to use RAM over the SPI lines. Does 
> there exist a RAM driver that can be altered (for example use the 
> internal ram as a chache, etc.).  If so which book or resource is a 
> good place to start reading?
you can use a framebuffer driver that uses normal ram for the
framebuffer, and a timer-controlled function copies the actual contents
to your controller via spi periodically. You can take a look at celinux
2.4 (www.celinux.org), there is such a driver in
drivers/video/hd66776fb.c. 

BTW, which controller are you talking about?

Regards,
Erwin
> 
> thank you very much in advance,
> 
> cheers,
> stef