Frequenzmesser bis 100Hz

[MagicWSmoke]

Dann versuch' Dich mal hiermit:

$regfile = "m32def.dat"
$crystal = 8000000
$hwstack = 64
$swstack = 64
$framesize = 64
Config Lcdpin = Pin , Db4 = Portd.4 , Db5 = Portd.1 , Db6 = Portd.5 , Db7 = Portd.0 , E = Portd.2 , Rs = Portd.3
Config Lcd = 16 * 2
Cursor Off

Const True = 1
Const False = 0
Const Measure_success = 0
Const Measure_failed = 1
Const Measure_request = 2

Dim Frequency As Long
Dim Capt_prev_val As Word
Dim Capt_curr_val As Word
Dim Measure_result As Long
Dim Capt_result As Word At Measure_result Overlay           ' Differenz aus Capture beschreibt das Low-Word von Measure_Result
Dim Ovf_result As Word At Measure_result + 2 Overlay        ' Mit dem Overflowergebnis das High-Word von Measure_Result beschreiben, spart das multiplizieren mit 65536
Dim Ovf_ctr As Word

Dim F_str As String * 10

' Variablen zur Ablaufsteuerung
Dim Got_edge As Byte
Dim Measure_status As Byte

Config Timer1 = Timer , Prescale = 1                        ' , Noise Cancel = 1     ' , Capture Edge = Falling       ' , Noise Cancel = 1

' Trigger durch Analogkomperator an Pin4, AIN1, AIN0 an Bandgap Reference 1V
Config Aci = On , Compare = On
Acsr.acbg = 1 

On Capture1 Isr_capt Nosave
Enable Capture1

On Ovf1 Isr_ovf
Enable Ovf1

Ovf_ctr = 0
Got_edge = False
Tifr = Bits(icf1 , Tov1)
Enable Interrupts

Initlcd
Cursor Off Noblink
Cls
Locate 1 , 1
Lcd "START"
Wait 2

Cls
Do
  Locate 1 , 1

  Measure_status = Measure_request
    While Measure_status = Measure_request
    Wend
      If Measure_status = Measure_failed Then
        Lcd "Timeout K.Erg."
      End If
      If Measure_status = Measure_success Then
        If Measure_result > 0 Then
          Measure_result = Measure_result / 10
'           Frequency = 826787928 / Measure_result           ' Kalibrierung für abweichenden internen RC Oszillator
           Frequency = 830996156 / Measure_result
'          Frequency = 800000000 / Measure_result
          F_str = Str(frequency)
            Lcd "Freq: " ; Format(f_str , "000.000") ; " Hz"
        Else
          Lcd "Fehler, Ergebnis = 0"
        End If
      End If
    Waitms 50
Loop

End

Isr_capt:
  PUSH    R22
  LDS     R22,                  ICR1L
  STS     {Capt_curr_val},        R22
  LDS     R22,                  ICR1H
  STS     {Capt_curr_val +1},     R22
  POP     R22
    Pushall
      If Measure_status = Measure_request And Got_edge = True Then       ' Messung angefordert und eine Flanke erkannt ?
        Capt_result = Capt_curr_val - Capt_prev_val         ' Ja, dann Werte übernehmen
          Measure_status = Measure_success
            If Capt_curr_val < Capt_prev_val Then           ' Natürlicher Overflow ?
              Decr Ovf_ctr                                  ' Bereichsgrenze überschritten, Overflows um 1 erniedrigen
            End If
          Ovf_result = Ovf_ctr
    End If
       Capt_prev_val = Capt_curr_val                        ' Aktuellen CAP-Wert speichern
         Ovf_ctr = 0                                        ' Overflowzähler zurücksetzen
           Got_edge = True
  Popall
Return

Isr_ovf:
    Incr Ovf_ctr
'      If Ovf_ctr > 122 Then                                 ' Niedrigste Messfrequenz 1 Hz unterschritten
      If Ovf_ctr > 126 Then                                 ' Korrektur für zu hohe RC Oszillatorfrequenz
        Got_edge = False
          Ovf_ctr = 0
            If Measure_status = Measure_request Then Measure_status = Measure_failed
      End If
Return

Edit:
µC wird momentan mit 'nem 16MHz Quarz betrieben, war noch so im Code gestanden, hab's geändert.
Musst die Werte halt auf 4MHz Takt anpassen.

EditEdit:
Hab' gerad' mal den ATMega8 als µC angegeben, das compiliert ohne Probleme. Es sollte also reichen den Takt auf 4MHz anzupassen, da ist nur:

Frequency = 830996156 / Measure_result
If Ovf_ctr > 126 Then

zu ändern. Dann LCD anpassen und der Analog-Comparator-Pin ist auch ein anderer.