門外漢的筆記

Arduino內建的函式myservo.write與myservo.writeMicroseconds都有最小正導通週期的限制，且限制最小值在550us，因此像SG90這種操作在500us~2000us之間並不適用。

而Arduino編輯程式不僅內建許多函式，也可以直接採用AVR的C Code。

從IC腳位來看，共有6組PWM Output可用，Timer 0(D5,D6)、Timer 1(D9,D10)、Timer 3(D3,D11)。

const int analogOutPin = 9; //宣告輸出PWM Pin=9
int outputValue = 0; 
int degValue = 0; 

void setup() {

pinMode(analogOutPin, OUTPUT);//設定Pin9為OUTPUT
  TCCR1A = ((1 << COM1A1) | (1 << WGM11)); // clear OC1A on match + WGM mode 14 
  TCCR1B = ((1 << WGM12) | (1 << WGM13) | (1 << CS11)); // WGM mode 14 (Fast PWM)
  ICR1  = 40000;  //set ICR1 to produce 50Hz frequency (16000000 / 8 / 40000 = 50hz)
  OCR1A = 2000;   // 40000 * 0.05 most left
}

// the loop routine runs over and over again forever:
void loop() {
      degValue=900;
      outputValue = map(degValue, 0, 1800,2000, 4000);
      OCR1A = outputValue;
      delay(2000);      
}

http://www.avrbeginners.net/architecture/timers/timers.html