Datasheet

Chapter 6 • Light-Sensitive Navigation with Phototransistors
206 • Robotics with the BOE Shield-Bot
Serial.begin(9600); // Set data rate to 9600 bps
}
void loop() // Main loop auto-repeats
{
float tLeft = float(rcTime(8)); // Get left light & make float
float tRight = float(rcTime(6)); // Get right light & make float
float ndShade; // Normalized differential shade
ndShade = tRight / (tLeft+tRight) - 0.5; // Calculate & subtract 0.5
int speedLeft, speedRight; // Declare speed variables
if (ndShade > 0.0) // Shade on right?
{ // Slow down left wheel
speedLeft = int(200.0 - (ndShade * 1000.0));
speedLeft = constrain(speedLeft, -200, 200);
speedRight = 200; // Full speed right wheel
}
else // Shade on Left?
{ // Slow down right wheel
speedRight = int(200.0 + (ndShade * 1000.0));
speedRight = constrain(speedRight, -200, 200);
speedLeft = 200; // Full speed left wheel
}
Serial.print(speedLeft, DEC); // Display speedLeft
Serial.print(" "); // Spaces
Serial.print(ndShade, DEC); // Display ndShade
Serial.print(" "); // More spaces
Serial.println(speedRight, DEC); // Display speedRight
delay(1000); // 1 second delay
}
long rcTime(int pin) // rcTime measures decay at pin
{
pinMode(pin, OUTPUT); // Charge capacitor
digitalWrite(pin, HIGH); // ..by setting pin ouput-high
delay(5); // ..for 5 ms
pinMode(pin, INPUT); // Set pin to input
digitalWrite(pin, LOW); // ..with no pullup
long time = micros(); // Mark the time
while(digitalRead(pin)); // Wait for voltage < threshold
time = micros() - time; // Calculate decay time
return time; // Returns decay time
}