Slow code needs a tune up

[Tobias]

16F877A measuring RPM. I have the timer style and PULSIN versions working fine. However my timer style of code is very slow. I toggle an output and on the scope I get 14 hz at 5000 rpm (4 counts/rev) when using the timer code. When I use the Pulsin I get 55 hz. Any ideas why its slower? I was under the impression the timer version would be alot faster than the Pulsin.

DEFINE OSC 20
RPM             var     word
Period          var     Word
HRPM            var     word
LRPM            var     word      
RPM_Total       VAR     Word
LCD             VAR     PortC.6    'LCD output  
RPMInput        var     PortC.2
Gate1           Var     PortC.1
Prefix          con      $FE             ' needed before each command
LcdCls          CON      $51             ' clear LCD (use PAUSE 5 after)
CursorPS        con      $45             'Cursor Position

pause 100
SEROUT2 LCD,84, [Prefix, LcdCls]

Include "modedefs.bas"	' Mode definitions for Serout

Low Gate1

OPTION_REG.7 = 0 'Pull Ups enabled
INTCON.7=0
ADCON0.0 =0
ADCON1 =7

Loop: 
If RPMInput = 0 then
  Pulsin RPMInput, 0, LRPM
  PULSIN RPMInput, 1, HRPM
  RPM_Total = HRPM + LRPM 
  RPM = 1000
  RPM = RPM * RPM
  RPM = DIV32 RPM_Total   ' 1,000,000 / Pulse_Total
  RPM = RPM * 60            ' Per minute
  RPM = Div32 8            ' 4 pulses per rev
endif

toggle  gate1

goto loop

DEFINE OSC 20
RPM             var     word
Period          var     Word
HRPM            var     word
LRPM            var     word      
RPM_Total       VAR     Word
LCD             VAR     PortC.6    'LCD output  
RPMInput        var     PortC.2
Gate1           Var     PortC.1
Prefix          con      $FE             ' needed before each command
LcdCls          CON      $51             ' clear LCD (use PAUSE 5 after)
CursorPS        con      $45             'Cursor Position

pause 100
SEROUT2 LCD,84, [Prefix, LcdCls]

Include "modedefs.bas"	' Mode definitions for Serout

Low Gate1

OPTION_REG.7 = 0 'Pull Ups enabled
INTCON.7=0
ADCON0.0 =0
ADCON1 =7

Loop: 
If RPMInput = 0 then
  Pulsin RPMInput, 0, LRPM
  PULSIN RPMInput, 1, HRPM
  RPM_Total = HRPM + LRPM 
  RPM = 1000
  RPM = RPM * RPM
  RPM = DIV32 RPM_Total   ' 1,000,000 / Pulse_Total
  RPM = RPM * 60            ' Per minute
  RPM = Div32 8            ' 4 pulses per rev
endif

toggle  gate1

goto loop

[Acetronics2]

Hi,

Just curious to know what you use as a sensor ...

Alain

[Tobias]

I am using an ignition simulator that is activating a racing ignition system. In essence the simulator triggers the points input on the ignition system. I am reading the tach output into an opto-isolator.

http://msdignition.com/Products/Igni...n_Control.aspx

http://msdignition.com/product.aspx?id=4777&terms=8998

[HenrikOlsson]

Tobias,
To me the two versions in your first post looks identical, am I wrong?

/Henrik.

[Tobias]

Yea I screwed that up here is the timer code

DEFINE OSC 20
Prefix          con      $FE             ' needed before each command
LcdCls          CON      $51             ' clear LCD (use PAUSE 5 after)
CursorPS        con      $45             'Cursor Position
Capture         VAR     PIR1.2		      ' CCP1 capture flag
Overflow        VAR     PIR1.0	    	' Timer1 overflow flag
RPM             var     word
period          var     Word
LCD             VAR     PortC.6    'LCD output
Gate1           Var     PortC.1
Gate2           var     PortD.1
Gate3           var     PortD.2
Gate4           var     PortD.3
Gate5           var     PortD.6
Gate6           var     PortD.7
Gate7           var     PortD.5
Gate8           var     PortD.4 
ADCON0 =0
ADCON1.3=1
ADCON1.2=1
ADCON1.1=1
ADCON1.0=1
TRISE.0=1
TRISE.1=1
CCP1CON = %00000110   			' Enable the CCP1 capture, every 4th rising edge
pause 100
SEROUT2 LCD,84, [Prefix, LcdCls]
low Gate1
Low Gate2
Low Gate3  
Low Gate4 
Low Gate5 
Low Gate6
Low Gate7  
Low Gate8 
loop:
T1CON = %00100000 ' TMR1 prescale=1:2 Timer OFF

'11 = 1:8 prescale value
'10 = 1:4 prescale value
'01 = 1:2 prescale value   '''
'00 = 1:1 prescale value
TMR1H = 0                               ' Zero the Timer
TMR1L = 0
capture = 0

Start:

	IF capture = 0 Then 
	  'SEROUT2 LCD,84, [Prefix,CursorPS,0,"RPM ",#0, " ", #Period] 
    goto Start	' Wait here for the first capture
  endif

 T1CON.0 = 1             ' Start the Timer
 capture = 0             ' Reset  the capture flag
  
CaptureLoop:
	IF capture = 0 Then 
    goto CaptureLoop	' Wait here until captured
  endif
  
period.lowbyte = CCPR1L		' Store the captured value in
period.highbyte = CCPR1H	' period variable

'period = period / 2
RPM = 10000
RPM = RPM * RPM ' 100,000,000
RPM = DIV32 period ' 100,000,000 / RevCount
RPM = RPM * 60 ' Per minute
RPM = DIV32 400
RPM = (RPM*5)

'SEROUT2 LCD,84, [Prefix,CursorPS,0,"RPM ",dec5 RPM, " ", #Period]

gosub cleartimer1    

GoTo loop					' Do it forever
    	
ClearTimer1:
IF (capture = 0) Then 
  goto cleartimer1	' Wait for beginning of next period
endif

TMR1L = 0					    ' Clear Timer1 low register
TMR1H = 0					    ' Clear Timer1 high register
capture = 0					    ' Clear capture flag
overflow = 0				    ' Clear overflow flagReturn
return

[Acetronics2]

One good reason could be the 2 DIV32 INSIDE the test loop ...

I measured once DIV32 took ~ 700µs ...

this is at least one very good reason for the PULSIN way to show a false result on the scope ... despite calculated RPM value to be right.

Alain

[Acetronics2]

With some little reflexion ....

I'd ask you to scope the signal you use from your gadget ...

Is it really a nice symmetrical square wave ???

Alain

[Tobias]

Its not a perfect function generator type square wave for sure. My scope has a USB output on it. This will be a good reason to learn how to send screen shots to my laptop. I will work on that tonite.