Page 40 · SumoBot – Mini Sumo Robotics
' -----[ Variables ]-------------------------------------------------------
irBits VAR Nib ' storage for IR target data
irLeft VAR irBits.BIT1
irRight VAR irBits.BIT0
' -----[ Program Code ]----------------------------------------------------
Main:
DO
FREQOUT LfIrOut, 1, 38500 ' modulate left IR LED
irLeft = ~LfIrIn ' read input (1 = target)
FREQOUT RtIrOut, 1, 38500 ' modulate right IR LED
irRight = ~RtIrIn ' read input (1 = target)
DEBUG HOME,
"L R", CR,
"----", CR,
BIN1 irLeft, " ", BIN1 irRight
PAUSE 20
LOOP
END
Two bit-sized variables are declared to store the value of each IR detector output. The
command
FREQOUT LfIrOut, 1, 38500 sends the [unfiltered] modulation signal
to the left IR LED, causing it to flash on and off rapidly. The harmonic contained in this
signal either bounces off an object, or not. If it bounces off an object and is seen by the
IR detector, the IR detector sends a low signal to I/O pin
LfIrIn. Otherwise, the IR
detector sends a high signal to
LfIrIn. The bitwise invert operator (~) is used so that a
"hit" (reflection from the opponent) is indicated by "1" and a "miss" is indicated by a "0."
So long as the next command after the
FREQOUT command is the one testing the state of
the IR detector’s output, it can be saved as a variable value in RAM. This is possible as
the IR detector output is held active a short time after the signal goes away. The
statement
irLeft = ~LfIrIn checks LfIrIn, and saves the value (“1” for hit or “0”
for miss) in the
irLeft bit variable. This process is repeated for the other IR pair, and the
IR detector’s output is saved in the
irRight variable. The DEBUG statement then displays
the values in the Debug Terminal.
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