Keyestudio Smart Little Turtle Robot V3 Manual page 70

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*/
int ledPin = 3; // Define the LED pin at D3
int value;
void setup () {
pinMode (ledPin, OUTPUT); // initialize ledpin as an output.
}
void loop () {
for (value = 0; value <255; value = value + 1)
{
analogWrite (ledPin, value); // LED lights gradually light up
delay (5); // delay 5MS
}
for (value = 255; value> 0; value = value-1)
{
analogWrite (ledPin, value); // LED gradually goes out
delay (5); // delay 5MS
}
}
(5) Test Result：
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