First post, by Rio444
Just I finished work on a prototype of an ISA PS/2 mouse card.
Photo of the prototype.
The scheme changed during the development process, so I had to use a wire.
The essence of the work of the adapter is that it "pretends" to be a COM port (chip 8250), and works with drivers for COM mice.
Unlike the well-known adapters PS/2 to COM port, data is transferred to the computer almost instantly and synchronously with data received from the PS/2 mouse.
Therefore, the response of the mouse does not differ in its sensations from the one working through the real PS/2 port.
The card consists of a module that works with the ISA bus - on the CPLD Altera EPM3064 (large chip on the left),
and a PS/2 mouse module that processes and converts the data from the mouse on the Atmega8 (second chip).
Now it was tested with 8 PS/2 mice, including ball, and modern, incl. using passive USB-> PS/2 adapter.
Systems: 286-8/16, 386DX-40 and Pentium-133 (430TX).
OS: MS-DOS 6.22 (more than 5 different drivers), Win 3.11, Win 95/98, WinNT 3.51.
Unfortunately, the card does not work in Windows XP.
Supported protocols: 3-button Logitech mouse, Microsoft mouse with wheel (selected by jumper).
The adapter can be setting on COM1 or COM2 port. At the same time, the corresponding port on the motherboard or multicard must be disabled.
Otherwise a port conflict will occur.
The card allows you to set the speed of the mouse: 100%, 75%, 50%.
For slow computers and fast mice, it is possible to transfer data not synchronously, and one data packet to COM for several packets from a PS/2 mouse: 1 data packet in a COM port per 2 received packets from a PS/2 mouse, 1 per 3, 1 per 4. This offloads slow processors (at least, slower than 386DX-20).