Parallax Boe-Bot - Page 265

Chapter 7: Navigating with Infrared Headlights · Page 251
FREQOUT 4, 2000, 3000 ' Signal program start/reset.
' -----[ Main Routine ]-------------------------------------------------------
DO
FREQOUT 8, 1, 38500 ' Store IR detection values in
irDetectLeft = IN9 ' bit variables.
FREQOUT 2, 1, 38500
irDetectRight = IN0
IF (irDetectLeft = 0) AND (irDetectRight = 0) THEN
GOSUB Back_Up ' Both IR pairs detect obstacle
GOSUB Turn_Left ' Back up & U-turn (left twice)
GOSUB Turn_Left
ELSEIF (irDetectLeft = 0) THEN ' Left IR pair detects
GOSUB Back_Up ' Back up & turn right
GOSUB Turn_Right
ELSEIF (irDetectRight = 0) THEN ' Right IR pair detects
GOSUB Back_Up ' Back up & turn left
GOSUB Turn_Left
ELSE ' Both IR pairs 1, no detects
GOSUB Forward_Pulse ' Apply a forward pulse
ENDIF ' and check again
LOOP
' -----[ Subroutines ]--------------------------------------------------------
Forward_Pulse: ' Send a single forward pulse.
PULSOUT 13,850
PULSOUT 12,650
PAUSE 20
RETURN
Turn_Left: ' Left turn, about 90-degrees.
FOR pulseCount = 0 TO 20
PULSOUT 13, 650
PULSOUT 12, 650
PAUSE 20
NEXT
RETURN
Turn_Right:
FOR pulseCount = 0 TO 20 ' Right turn, about 90-degrees.
PULSOUT 13, 850
PULSOUT 12, 850
PAUSE 20
NEXT
RETURN