Earlier today I found this design for a lightpen to HID adapter. I haven’t picked up a lightpen yet, but it seems like as long as you found one compatible with that adapter design it would be a simple drop-in replacement for a mouse, so you could theoretically use it with Scrawl and draw straight on the CRT just like old video paint hardware, which would be pretty fun.
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wow that would be amazing
I’ve been meaning to remake scrawl in touchdesigner for some time. I’ve been too deep into hardware lately but I’m sure I’ll take another softer dive before too long.
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I foudn someone on eBay selling two new-old-stock, early 90s lightpens for $16 each plus shipping. I jsut bought one of them but there’s another left if anyone else is interested. I have no idea if they’re compatible with that circuit I posted, but I think by the 90s it was pretty much a standard device, like a serial mouse.
EDIT:
I was trying to see if that light pen was Atari ST compatible since that would be another way to use it if it doesn’t work well with the Pi adapter, and I found this old article about making an entire DIY light pen from scratch:
https://www.atariarchives.org/creativeatari/Build_Your_Own_Light_Pen.php
I bet it wouldn’t be too hard to port the code over to the Raspberry Pi and actually make a native light pen for it. The actual hardware is nothing - just a photo cell and resistor mounted in an old penlight body. It might take some trial and error to find a cell that responds quickly enough to be reliable I guess, but it would still be easier than building the adapter for a commercial light pen. I doubt I’ll try it myself, but it seems promising.