[openpsion] Storage for revo

[Ed R. <edw...@ti...>]

IIRC all the smaller Psion machines (5,5mx,revo etc) use the SPI bus for
several peripherals like touchscreen etc. If there is a spare GPIO pin to=

use for a chip select could we not use some kind of SPI memory as storage=

(e.g. MMC, SD card in SPI mode)? Problems I can think of are:

-Not sure IIRC! Maybe the psion uses the SSI bus - are there any SSI stor=
age
devices? We can probably convert from SSI to SPI if not - they are very s=
imilar.

-Not certain there are spare GPIO pins for a chip select. However, I for
one dont mind going without the modem control signals on the serial port
(why would I use a modem these days!?)

-Not sure what effect having a storage device on the bus would have on ba=
ndwidth
available for other peripherals but I suspect this may be the real proble=
m.
Either way I also suspect that data transfer speeds would be chronic.

Another solution:

Implement a seperate SPI bus on spare GPIO pins or disconnect the modem c=
ontrol
lines and use those. We need 3 pins (not including chip select which coul=
d
just be tied high if we have just one device) in order to make this work.=

Should give a much better transfer rate.

I am not really able to do software (I explify the term kernel hacker in
that I can only hack kernel code, not write it!). How possible/difficult
would something like this be to implement? Is there a suitable SPI driver=

available which can just be told which GPIO pins to use? Any other proble=
ms/ideas
anyone can think of? I'm thinking along the lines of a Revo with SPI base=
d
mass storage and a serial based bluetooth device (hence I really wouldnt
need the modem control lines at all), or a 5mx with a wireless cf card an=
d
a seperate storage card.

Maybe I've really lost it this time...but its nice to dream!

Regards,

Ed.

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