Are you low on IO ports and want to add several buttons to
you microcontroller project? This approach works quite well.
By using the pot command we can add many buttons to a single IO port.
The pot command charges a capacitor then determines how
long it takes to discharge. By placing a resistor across the
capacitor you can control the time it takes to discharge therefore the
reading of the pot command. In this case we will use a .1uf capacitor and
various resistors connected to buttons.
Athena Hookup
By using different values you can determine which button
is being pressed.
The Program (download
it here)
'Multi Button
dim button
LOOKDOWNMODE=1
loop:
gosub getbutton
if button = 0 then
goto loop
endif
print "button=",button
goto loop
getbutton:
pot 0,4,button
lookdown button,button,5,10,22
if button = 0 then
return
endif
return
We used a lookdown command to convert the actual pot
values to button numbers. In this case the actual values were
5,10,22. You will have to test for the resistors you use and
change the lookdown command appropriately. Place a print x command
in front of the lookdown command to display the raw readings.
What about reading two switches at the same time?
With the right resistor combinations this can be done. For example
pushing button 1 and button 2 the raw reading is 4. Pushing button 2
and button 3 the reading is 7.
Parts
Easy RS232 Driver
Athena
Athena EDU
Breadboard Push
Button
7.5V AC Adapter
9 Pin Cable
Breadboard and
Wire Kit
Breadboard
Regulator
