Keyestudio Smart Little Turtle Robot V3 Manual page 79

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Serial.print("left:");
Serial.print(val_L);
Serial.print(" middle:");
Serial.print(val_M);
Serial.print(" right:");
Serial.println(val_R);
delay(500);// delay in between reads for stability
}
//****************************************************************************
(6) Test Result：
Upload the code on development board, open serial monitor to check line
tracking sensors. And the displayed value is 1(high level) when no signals
are received. The value becomes into 0 when covering sensor with paper.
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