It was literally encoders and buttons wired out to a DIN-9 plug. The bus mouse itself had no active components. Put one encoder on a vertical axle, and another on a horizontal axle, and you can then determine XY motion distance and direction. Every edge is a count, although usually there is one bit of hysteresis to avoid jittering if the mouse stops on an edge. It’s probably described elsewhere, but quadrature signaling is two square waves with 90° phase between them, such that if A leads B, you are moving clockwise, and if B leads A, you are moving counterclockwise. However, because of the dogleg, there is a 90° phase shift between A and B. So what happens is, A and B have pullups on them and will generate a square wave on the brush when rotated as the brush hits the ground trace on the wheel. Then about a third of the way out a brush (the A signal), then two thirds of the way out another brush (the B signal) that picks up the trace after the dogleg. One toward the center that contacts the ring. Then, in the sensor there are three brushes. On that disk are traces that look like spokes emanating from a solid ring near the axle, but about halfway out, they dogleg a bit, and then continue out to the edge. I have one in a box somewhere, Envision an axle with a disk on the end, kind of like a dremel cutoff bit. Posted in classic hacks Tagged mouse, PS/s mouse, ps2, rs232, RS232 mouse, serial mouse, usb mouse Post navigation If you have one of those machines from that era that came with proprietary interfaces, maybe you can make use of a USB to quadrature converter. The supply of still-reliable RS232 mice must therefore be dwindling, and if you have a Windows 3.1 PC to keep alive then we can see the ability to use a more modern pointing device has a lot going for it. In the early 1990s mice were not the reliable optical devices we have today, instead they had nasty mechanical connections inside, or if you were extremely lucky, optical encoder wheels. It might sound like a rather unexpected device to produce, but we can see it fills an important niche. He’s created a PS/2 to RS232 mouse converter, and it takes the form of a little PCB with an AT90S2313P microcontroller to do the translation and an RS232 level converter chip. Happily, has come along with a solution for those of you with a need to drive an ancient PC with a serial mouse. Want to run Windows 3.1 on a 386DX? You need a serial mouse. It is unlikely then that you could take a modern USB-only device and an unholy chain of USB-to-PS/2-to-serial adapters, and have it work as a serial mouse. Those mice from a decade or more ago would have contained the software to recognise the interface into which they were plugged, and emulate it accordingly. And if you were to go back a few more years into the past, you’d have found when you bought a mouse with a PS/2 connector fitted, it may well have come with an adapter for a 9-pin RS232 serial port. When did you last buy a mouse? Did it have a little adapter in the box? There was a time when if you bought a USB mouse, in the box was also an adapter to allow it to be used with the older PS/2 interface.
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