Mastodawn

So who knows stuff about the #commodore64 light pen?

Was there an amplification circuit for the light sensor input?

It clearly is responding when I point it up at my task light, but it's barely 30mV. Just no idea if that's what I should be seeing. Also no idea why the 'floor' goes negative...

One button is 5V high and properly drops to 0 when pressed as expected. the other button doesn't seem to work, but the CGA only supported one button anyway.

#retrocomputing

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Gummilover

@gloriouscow as far as is remember, it should detect the electon beam in the CRT. the timing where the actual point is lit, tells the computer where the pen was pointing. (same principle as the pen for the amstrad computer in this time)

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gloriouscow 4d ago

@gummilover right - i know the theory of operation, enough to have emulated the IBM PC light pen even, just needed to sort out the electrical specifics.

I think we've got it sorted but i'll have to mess with it more tomorrow.