LisaList2
General Category => LisaList2 => Topic started by: stepleton on October 21, 2023, 07:49:11 am
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Yesterday I experimented with the Raspberry Pi-based RGBTOHDMI device (https://github.com/hoglet67/RGBtoHDMI), which plenty of folks out there are using to interface lots of older systems with modern displays. (You can buy complete or add-your-own-RPi kits from various online "retro" shops, or you can build your own if you like SMD soldering.) There are folks out there who've managed to get it working with their Lisas, and after a lot of fiddling, I was able to do it too; see attached image.
The device seems to produce a good result if you are patient and lucky. There seem to be one or two dozen parameters you can set which will directly affect the quality of the image you get. The project's own "Apple Lisa" profile produced a skewed, rolling image for me, and I had to spend a good hour poking around and trying different options until I got something to work. (One of the parameters had me tuning an hsync-detection threshold to somewhere inside a 20 millivolt sweet spot.) I'm not sure how reproduceable the result is across Lisas or across separate RGBTOHDMI devices.
But the settings I wound up with seem dependable for now, and it's the only tool I have for getting the Lisa to display on something from this century.
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Terrific work on getting your display working with the Lisa! I had slightly different values than DosFox. Here's what I had using 8 bit analog YUV:
sampling=7,7,7,7,7,7,7,0,1,0,10,0,0,0,0,4,1,1,1,0,79,256,256,256,256,39,256,256
geometry=164,7,552,364,720,364,2,3,1,1,20374338,896,5000,379,4,0,0
palette=Mono_(2_level)
scanline_level=0
Curious if mine is different in any way because I'm using an EPROM for the VSROM perhaps?
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This looks like it would be a lifesaver in the event of a dead CRT.
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In the event of a dead CRT, use some other 12" paperwhite tube as a replacement. E.g. from an Atari SM124 monitor. These have better brightness and focus than the original Clinton tube used by Apple.
In the event of some other hardware issue, just install LisaEm on your Raspberry ;)
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Terrific work on getting your display working with the Lisa! I had slightly different values than DosFox. Here's what I had using 8 bit analog YUV:
sampling=7,7,7,7,7,7,7,0,1,0,10,0,0,0,0,4,1,1,1,0,79,256,256,256,256,39,256,256
geometry=164,7,552,364,720,364,2,3,1,1,20374338,896,5000,379,4,0,0
palette=Mono_(2_level)
scanline_level=0
Per this old post (https://lisalist2.com/index.php/topic,341.msg2423.html#msg2423), I suspect the aspect ratio of a single pixel on real Lisa hardware is more accurately 3:4 (Horizontal:Vertical)... if one of you that has an RGB2HDMI connected to a Lisa could try that and report as to whether it looks closer to the real thing it may pacify my curiosity. (Various screen images posted in the AppleLisaClone threads look too tall, but there are numerous other explanations of course.)
eg. geometry=164,7,552,364,720,364, 3, 4 ,1,1,20374338,896,5000,379,4,0,0
Curious if mine is different in any way because I'm using an EPROM for the VSROM perhaps?
What speed is your EPROM? I'm wondering if a slow video state machine works just as well as a stock one, perhaps only causing a delay in the retrace signals?