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VISUAL
FEEDBACK
I
have to admit that relying on an application to
provide position feedback isn't the user-friendliest
option. So what kind of options might be useful
with your interface?
The
obvious choice is to hang an LED/LCD panel meter
on the output of each DAC. But this is an expensive
solution and doesn't work well with the digital
potentiometer solutions. A reasonable alternative
would be a multi-digit LED display (an LTC4627 costs
$2.40 from Digi-Key).
Substituting
a microcontroller with more I/Os isn't a big deal
either. For the most part, the peripherals can boost
microcontroller costs, not just the number of I/Os.
The PIC16F505 costs $1.75 versus the PIC16F57, which
costs $2.73.
With
a circuit similar to the one in Figure 7, the position
(XVal) can be displayed while an adjustment is being
made. The display could alternate display values
for multiple axes. Center off values can be presented
by displaying –127 to 128.
|
(Click
here to enlarge)
|
Figure
7—A multiple hex-digit LED display can provide
position feedback of the present value for any
device. Although it can show only one device's
value at a time, you might choose to rotate
through the value of each device, show the value
of the last device, or even blank after adjustments
are complete. |
Creativity
reigns when designing user interfaces. If you've
had a chance to play with an iPod, you know what
I mean. It isn't what you have to work with, but
how you use it.
