Page 204 · Robotics with the Boe-Bot
Boe-Bot should move forward. If you cast a shadow over one of the photoresistors, the
Boe-Bot should turn in the direction of the photoresistor that senses the shadow.
√ Enter, save, and run ShadowGuidedBoeBot.bs2.
√ Use your hand to cast shadows over the photoresistor dividers.
√ Study this program carefully and make sure you understand how it works. It is
very short, yet very powerful.
' Robotics with the Boe-Bot - ShadowGuidedBoeBot.bs2
' Boe-Bot detects shadows cast by your hand and tries to follow them.
' {$STAMP BS2} ' Stamp directive.
' {$PBASIC 2.5} ' PBASIC directive.
DEBUG "Program Running!"
FREQOUT 4, 2000, 3000 ' Start/restart signal.
DO
IF (IN6 = 0) AND (IN3 = 0) THEN ' Both detect shadows, forward.
PULSOUT 13, 850
PULSOUT 12, 650
ELSEIF (IN6 = 0) THEN ' Left detects shadow,
PULSOUT 13, 750 ' pivot left.
PULSOUT 12, 650
ELSEIF (IN3 = 0) THEN ' Right detects shadow,
PULSOUT 13, 850 ' pivot right.
PULSOUT 12, 750
ELSE
PULSOUT 13, 750 ' No shadow, sit still
PULSOUT 12, 750
ENDIF
PAUSE 20 ' Pause between pulses.
LOOP
How ShadowGuidedBoeBot.bs2 Works
The IF…THEN statement in the DO…LOOP looks for one of the four possible shadow
conditions: both, left, right, neither. Depending on which condition is detected,
PULSOUT
commands deliver pulses for one of the following maneuvers: forward, pivot right, pivot
left, or sit still. Regardless of the condition, one of the four sets of pulses will be
delivered each time through the
DO…LOOP. After the IF…THEN statement, it’s important to
remember to include the
PAUSE 20 to ensure the low time between each pair of servo
pulses.
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