Re: recommendations for a response box with a knob

[Owen Brimijoin <owen@xxxxxxxxxxxxx>]

Hi Brian,
If you want ultra cheap, then you can use the scroll wheel on a USB 
mouse. Matlab can capture scrolling events and update a variable if you 
include a WindowScrollWheelFcn function in your code:

%--------------------------------
function dial_plotter_example
global dial_value
dial_value = 0;
h = figure; set(h,'WindowScrollWheelFcn',@figScroll)

while ishandle(h),
    scatter(dial_value,0,'filled'); axis([-10 10 -10 10]);
    pause(0.001)
end

function figScroll(src,evnt)
global dial_value
dial_value = dial_value + evnt.VerticalScrollCount;
%--------------------------------

We went as far as to disassemble the mouse and stick it in a nice 
project box. We rewired the 3  mouse buttons to buttons on the top, 
mounted the scroll wheel encoder vertically underneath the lid, and 
attached a big appealing dial on top. Presto! a 3-button box with a dial 
and a remarkably low latency response - and how much does a USB mouse cost?

all the best,
-Owen.

ps. this will not work in older versions of Matlab. I don't remember in 
which version WindowScrollWheelFcn was added. It doesn't work in r14.

--
_________________________________

W. Owen Brimijoin
MRC Institute of Hearing Research
Scottish Section
Glasgow Royal Infirmary
Glasgow, United Kingdom
owen@xxxxxxxxxxxxx
_________________________________