This is the specification, in fact 9 V suffices with most
The mouse driver can recognize a mouse by dropping RTS to
low and raising it again. About 14 ms later the mouse will
send 0x4D (’M’) on the data line. After a
further 63 ms, a Microsoft-compatible 3-button mouse will
send 0x33 (’3’).
The relative mouse movement is sent as dx
(positive means right) and dy (positive means down).
Various mice can operate at different speeds. To select
speeds, cycle through the speeds 9600, 4800, 2400 and 1200
bit/s, each time writing the two characters from the table
below and waiting 0.1 seconds. The following table shows
available speeds and the strings that select them: