Parallax BASIC Stamp 2e Programming Manual page 92

COUNT - BASIC Stamp Command Reference
If you use COUNT on slowly changing analog waveforms like sine waves,
you may find that the value returned is higher than expected. This is
because the waveform may pass through the BASIC Stamp's 1.4-volt logic
threshold slowly enough that noise causes false counts. You can fix this by
passing the signal through a Schmitt Trigger, like one of the inverters of a
74HCT14.
Demo Program (COUNT.bs2)
Connect the active-low circuit shown in Figure 5.1 (BUTTON instruction) to pin P0 of the BS2.
The Debug screen will prompt you to press the button as quickly as possible for a 1-second
count. When the count is done, the screen will display your "score," the total number of
cycles registered by COUNT. Note that this score will almost always be greater than the
actual number of presses because of switch bounce.
'{$STAMP BS2}
Cycles var word
Loop:
DEBUG cls,"How many times can you press the button in 1 second?",cr
PAUSE 1000
DEBUG "Ready, set... "
PAUSE 500
DEBUG "GO!",cr
COUNT 0,1000,Cycles
DEBUG cr,"Your score: ", DEC Cycles,cr
PAUSE 3000
DEBUG "Press button to go again."
Hold:
IF IN0 = 1 THEN Hold
GOTO Loop
Page 90 • BASIC Stamp Programming Manual 2.0b • www.parallaxinc.com
'STAMP directive (specifies a BS2)
' Variable to store counted cycles.
2 2 2
2
e
sx p
NOTE: This is written for the BS2
but can be used for the BS2e,
BS2sx and BS2p also (with
modifications). Locate the proper
source code file or modify the
STAMP directive and the period of
the COUNT command before
downloading to the BS2e, BS2sx or
BS2p.