[maemo-developers] [maemo-developers] Specification for Epson S1D13742 Mobile Graphics Engine

[From: Frantisek Dufka]

Hello,

I've got good news. Few days ago I tried to contact once again Epson 
Electronics (last time I tried got no reply) and today I got nice 126 
pages long specification PDF with register description and other 
programming information. If someone is interested, let me know. I was 
not told to keep it secret or anything so I guess I can resend it to 
people interested. Not sure if putting it freely to website isn't too much.

Looks like the rotation mode is two lowest bits in one register at 
offset 34h

00 0 degrees(Normal)
01 90 degrees
10 180 degrees
11 270 degrees

and in theory can be simply enabled and all display updates are 
transparently rotated. I'll try it.

It also looks like there is register (offset 58h) which contains display 
(vertical) blank timing information - 2 read only bits (number 7 and 6) 
- bit contains 1 when display is in vertical/horizontal non-display 
period. Also the chip has TE (tearing effect) output pin which can be 
configured to signal this condition but it is hard to say whether it can 
triger interrupt or whether it is connected to anything at all in N770. 
But still it can be possible to check these bits (mainly the vertical 
one) in register and try to synchronize display updates with it to 
minimize tearing.

There is also double buffering functionality but it works only in lower 
resolutions, not 800x480 (as there is no memory for 2 buffers) and I 
guess LCD supports only 800x480. Maybe timing for one line can be 
doubled to have 400x480 and then enable double buffering? Probably not.

Frantisek