The "quickly flying light dot" is how the picture was drawn on a CRT, so it didn't have to do anything special. The light pen simply reported to the video card "I saw the dot", and the board would then store somewhere the exact x/y position that it was drawing when the pen fired. This is how the gun for the NES worked, as well as various other such instruments for other computers. I remember the C64 having such, also.
It probably wasn't a great idea to stand that close to a CRT for extended periods of time. Michael On Mon, Sep 9, 2013 at 3:00 PM, Jack Coats <[email protected]> wrote: > The other day I ran into my doc's about CGA displays, including the > lightpen input. The light pen was a photo transistor and a switch > that signaled the CGA board the light pen was pressing on the glass > screen. The CGA display actually did the scanning (with a quickly > flying 'light dot' to find the pen position) and reported it back to > the computer through the CGA display card. > > Now back to your daily dose of non-bone-kives-and-bear-skin-technology. > > -- > -- > You received this message because you are subscribed to the Google Groups > "NLUG" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/nlug-talk?hl=en > > --- > You received this message because you are subscribed to the Google Groups > "NLUG" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > -- Michael Darrin Chaney, Sr. [email protected] http://www.michaelchaney.com/ -- -- You received this message because you are subscribed to the Google Groups "NLUG" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nlug-talk?hl=en --- You received this message because you are subscribed to the Google Groups "NLUG" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
