Datasheet

Light-Sensitive Navigation with Phototransistors • Chapter 6
Robotics with the BOE Shield-Bot • 199
/*
* Robotics with the BOE Shield - LightSensorValues
* Displays tLeft, ndShade and tRight in the Serial Monitor.
*/
void setup() // Built-in initialization block
{
tone(4, 3000, 1000); // Play tone for 1 second
delay(1000); // Delay to finish tone
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
// Display heading
Serial.println("tLeft ndShade tRight");
Serial.print(tLeft); // Display tLeft value
Serial.print(" "); // Display spaces
Serial.print(ndShade); // Display ndShade value
Serial.print(" "); // Display more spaces
Serial.println(tRight); // Display tRight value
Serial.println(' '); // Add an extra newline
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
}