28 Dec
2012
28 Dec
'12
8:08 p.m.
On 12/28/2012 06:56 PM, Mouse wrote:
More than slightly. Most versions ideally place them 90 degrees out of
phase with one another. This has two advantages: (1) it maximizes the
minimum time between seeing one edge and seeing the next, and (2) if
you count all four edges per cycle instead of two or one, using 90
degrees of phase shift gets you more regular counting.
(1) is admittedly not very relevant if you're using a real mouse and
even vaguely modern electronics, since on even a high-res mouse edges
are very far apart on digital logic timescales.
Did you catch the ID in EDN about 6 months ago for a circuit using a
single 4538 on a rotary encoder that provides pulses on either of two
lines depending on direction? I thought it was very clever--much better
than the usual flip-flop decoder.
--Chuck
Aren't they called 'quadrature' mice or
something like that?
Exactly. each has two outputs, spaced slightly out of phase
with
each other.