If you worked with pcs back in the 1970s, there is a excellent prospect you used a light-weight pen at some level: a straightforward input system that you’d stage at the CRT display to emphasize textual content, decide on menu solutions or manipulate graphic objects. Although ubiquitous in people times, the light pen shed the fight for ergonomics to the humble mouse and was all but extinct by the late 1980s. Touchscreen styluses put into action a identical purpose right now, but touching the monitor somehow doesn’t come to feel the identical as simply just pointing at it.
We therefore applaud [Maciej Witkowiak]’s attempts to deliver the light-weight pen into the 21st century by making a USB interface for a Commodore 64/128 mild pen. At its heart is an Arduino Micro Professional that implements the USB HID protocol to talk with any modern pc. It connects to the basic gentle pen as properly as to the computer’s analog screen sign and utilizes those to calculate the delay amongst the video clip synchronization pulses and the mild pen’s output. The sync pulses are extracted from the video signal by an LM1881, a sync separator chip that will be common to everyone who’s worked with analog video indicators.
The Arduino calculates the light-weight pen’s position dependent on the measured timing intervals and reviews it to the personal computer, utilizing the complete positioning method which is also utilised by items like drawing pads. [Maciej] demonstrates his technique in the movie embedded underneath, in which he works by using it to operate the menus on an X window system. A fantastic good results then, while there is 1 capture: light-weight pens only function on CRT displays, so you will have to have to drag a person of these big glass beasts out of storage if you want to attempt this yourself.
We’ve highlighted the Commodore mild pen before in this odd gaming input system. A very similar product created with a discrete LED matrix is a good illustration of the mild pen’s doing the job principle.