General Category > Lisa Project Ideas

LisaHDMI (or VGA)

<< < (2/2)

rayarachelian:
Excellent, thank you!

Edit: Actually, you've put up a line for the DOTCLK there, that's a good point I've missed with this project idea, if there's a clock to time off of, it's well worth using it (perhaps with a counter to divide it down as needed.)

Lisa2:

--- Quote from: sigma7 on October 28, 2022, 11:57:18 pm ---I think this is the pinout for J18...
it would be wise to verify for yourself of course.

--- End quote ---
James,
I did check the PCB and those are the correct pinouts.
Thanks,
Rick

andrew:

--- Quote from: sigma7 on October 26, 2022, 05:54:52 pm ---...
I wondered what this would look like on a 1200x1920 monitor so I made a graphic rectangle that size. Seems like a reasonable size to look at in spite of the big border, but surprise, it doesn't look right!

The actual size of the physical image the Lisa is supposed to have on screen is defined by an Apple service part #077-8043-A, which is a graticule overlay. I've never seen one and I haven't been able to find any documents as to its measurements.

Next best I can do is to measure the opening in the front panel, and to me it looks like an image of 6" x 9" would fit nicely. (Hmmm... 2:3 ratio)

720 pixels in 9" is 0.01250" per pixel
364 pixels in 6" is 0.01648" per pixel

and  0.01648 : 0.01250 is a ratio of 1.318, not 1.5

If the specification of a Lisa pixel is actually a ratio of 4:3 then given
720 pixels in 9" is 0.01250" per pixel (width)
364 pixels at 4:3 would be 0.01667" per pixel (height) and that would result in the raster being 6.0667" high.

So I believe the correct description of the Lisa video is a H:W ratio of 2:3 for the entire raster, with each pixel being a rectangle of 4:3 H:W
...

--- End quote ---
There are a few graphical elements within LOS which seem to very strongly favor a 2:3 pixel aspect ratio: the "NOTE" square (72 x 48 px), the "Stop" octagon (102 x 68 px), and the grid pattern on the LisaDraw canvas (48 x 32 px) all have raw pixel dimensions with a 2:3 ratio and are elements which should be displayed at a 1:1 ratio. The difference between the raw width of vertical scrollbars and the raw height of horizontal scrollbars is also 2:3 (24 px vs 16 px). This makes for a neat grid within windows with square buttons for the scroll arrows and the resize drag button.


I am getting my dimensions from raw screenshots I took in LisaEm.

Navigation

[0] Message Index

[*] Previous page