用可變電阻器+減速電機做伺服電機
        $regfile = "m8def.dat"                              '目標單片機為ATmega48
                       $baud = 9600
                       $crystal = 8000000                   '使用內部8M晶振
                      ' Config Serialout = Buffered , Size = 20


                       $prog &HFF , &HE2 , &HDF , &HFF      '單片機熔絲位參數設置:禁止系統時鐘8分頻
Config Adc = Single , Prescaler = Auto , Reference = Avcc
'設置ADC為單次轉換模式，采樣頻率有編譯器自動選擇，參考電壓使用AVcc
                                                       '下降觸發
       Config Timer1 = Timer , Prescale = 1024 , Capture Edge = Falling , Noice Cancel = 1
                     '計時器1計時

Dim A As Byte
Dim W As Integer
Dim X As Integer
Dim M As Integer
Dim S As Word
Dim R As Integer
Dim Q As Long
Dim F As Long
Dim I As Long
Dim C As Byte
                                        '下降沿中斷開

                                            '計時器1中斷開
On Icp1 Icp_isr

                                                '使能
Enable Capture1

Enable Interrupts



      Timer1 = 0
                                         '裝入計時器初值
      Start Timer1


  Ddrb = &B00000010

Ddrd.6 = 1
 Ddrd.7 = 1
Portd = Portd And &B00000000
 Start Adc                                                  '啟動ADC轉換,adc電阻與一個直流減速電機同軸
    Q = 0
    F = 0'可為預先設頻率355
    W = 0
     S = 0


 Do
     Q = Getadc(0)


     Print Q


If W = 0 Then   '測得兩次的pwm值，當小于 65536（timer1溢出）時,測得值+65536-舊值，否則新值-舊值
 s=w
  Else
      If S = W Then Goto Lp
    If S > W Then
    S = 65536 - S
    F = S + W
    Else
    F = S - W

    End If
W = 0
end if

lp:

          If Q <> F Then


              If Q > F Then
 Reset Portd.6
 Set Portd.7
 End If

      If Q < F Then                                         '設置PD6,7口為輸出驅動電機,伺服電定位于指定角度
      Reset Portd.7
      Set Portd.6
  End If
  End If


     Loop
      End




      Icp_isr:
       S = Capture1
         Return