unit uICP;
{ $NOSHADOW} 									// Comment this CompilerConst out, to enforce full register saving in the interrupt. Do this in the MAIN program too!

interface                                                                       // DO NOT FORGET to set the ICP1 Pin to INPUT in the DDR!

{$IDATA}

Var
   icp_period_buf, delta_buf : AVFilter [0..7] of Word;
   iprescale : Byte;
   iiSerPortDSR : Byte;

procedure InitTimer1Int;                                                        // Initialize the Time1 for Freq./PWM counting
function get_Freq : Float;                                                      // Get the current Frequency in Hz
function get_PWM : Float;                                                       // Get the current PWM in %

implementation

Var
   icp_start_time, icp_stop_time, icp_period, delta, icr : Word;


Interrupt Timer1CompA;                                                          // Overflow of Timer1, because no Pulse came in: so reset the Prescaling-Window
begin
   iprescale := TCCR1B AND $07;
   if (iprescale < 5) then
      iprescale := iprescale + 1;
   EndIf;
   TCCR1B := (TCCR1B AND NOT $07) OR iprescale;
end;


Interrupt Timer1Capt;                                                           // This Interrupt is called depending on the frequency at the Int/Capt Input.
begin
   icr := ICR1;									// save immediately the current Timer-Count
   if ((TCCR1B AND $040) = 0) then					        // Interrupt was on falling edge
      icp_stop_time := icr;					                // Pulse has stopped: save the stop time
   else
                                                                                // Interrupt was on rising edge
      icp_period := icr - icp_start_time;		                        // calculate length of the full PWM-period
      delta := icp_stop_time - icp_start_time;                                  // calculate length of the previous pulse
      AddAVFilter(icp_period_buf,icp_period);
      AddAVFilter(delta_buf,delta);
      OCR1A := icr + 60000;					                // Assume the maximum timeout for the next pulse transition
										// if within 60.000 Timer tics no transision occurs, the
										// TIMER1_COMPA_vect Interrupt will fire!
      if (icp_period < 2000) then					        // 2.000 x 8 = 16.000 --> maximum jump, because
										// maximum factor is 8. Empirically tested, don't use
										// greater values...
         TCCR1B := (TCCR1B AND NOT $07) OR 1;		                        // reset the scale to 1 and let the TIMER1_COMPA_vect
										// do the adjustment of the best (=finest) scale
										// since there is o prescale now, the timer runs
      endif;									// as fast as possible, so the adjustment is fast too!
      icp_start_time := icr;					                // Start of new pulse/period: save the new start time
   EndIf;
   TCCR1B := TCCR1B XOR $040;						        // Reverse Bit 6 = Interrupt on rising / falling edge
end;


function get_Freq : Float;
Var
   lCnt : Byte;
   lips, lFreq : Float;
   lprescale, lScaleMask : Word;
begin
   lprescale := 1;
   lFreq := ProcClock;
   lScaleMask := Word(TCCR1B AND $07);

   lips := Float(GetAVFilter(icp_period_buf));

   if (lScaleMask = 1) then lprescale := 1; endif;
   if (lScaleMask = 2) then lprescale := 8; endif;
   if (lScaleMask = 3) then lprescale := 64; endif;
   if (lScaleMask = 4) then lprescale := 256; endif;
   if (lScaleMask = 5) then lprescale := 1024; endif;
   if (lips > 0) then
      lFreq := Float(lprescale) * lFreq / lips;
   else
      lFreq := 0;
   EndIf;
   Return (lFreq);
end;
                                                                          	// *******************************************************
                                                                                // * calculate Pulse Width in % from the Interrupt values
                                                                                // *******************************************************
function get_PWM : Float;
Var
   lCnt : Byte;
   lPWM, lips : Float;
begin
   lPWM := 0;
   lips := 0;

   lPWM := Float(GetAVFilter(delta_buf));
   lips := Float(GetAVFilter(icp_period_buf));

   if (lips > 0) Then
      lPWM := lPWM / lips;
   else
      lPWM := 0;
   EndIf;
   Return (lPWM);
End;

procedure InitTimer1Int;
Var
   lCnt : Integer;
begin
        TIMSK1 := TIMSK1 AND NOT $022;						// DISABLE Input Capture Interrupt and Output Compare A Match Interrupt
	icp_start_time := 0;
	icp_stop_time := 0;
	icp_period := 0;
	delta := 0;

        PresetAVfilter(icp_period_buf,0);
        PresetAVfilter(delta_buf,0);

	TCCR1A := 0;								// Timer 1: nothing set!
	TCCR1B := $041;								// Interrupt on rising edge, set prescaler = 1
										// Timer in Normal Mode, Incrementing, Timer overruns 0xFFFF to 0x0000
										// Pins OC1A and OC1B disconnected
	OCR1A  := 0;								// Timer 1: Output Compare Register: nothing to set!
        TIMSK1 := TIMSK1 Or $022;						// Input Capture Interrupt Enable and Output Compare A Match Interrupt Enable
										// 0x20 = ICF1  for enabling the TIMER1_CAPT_vect
end;

initialization

finalization

end.