Slow code needs a tune up

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- 5th January 2010, 08:51
Tobias

Slow code needs a tune up

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.

Code:

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

Code:

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
- 5th January 2010, 09:22
Acetronics2

Hi,

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

Alain
- 5th January 2010, 10:08
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
- 5th January 2010, 10:38
HenrikOlsson

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

/Henrik.
- 5th January 2010, 10:45
Tobias

Yea I screwed that up here is the timer code

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
- 5th January 2010, 13:41
Acetronics2

method problem ...

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
- 5th January 2010, 14:23
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
- 5th January 2010, 15:05
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.