Using CCP1 and CCP2 to measure instant fuel consumption

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- 19th July 2007, 14:45
srspinho

Using CCP1 and CCP2 to measure instant fuel consumption

Hello friends,

some time ago, I did a digital speedometer for my car using the following code to count pulses (written by Tim_B for Proton Basic)

==============================================

Define LCD_DREG PORTA
Define LCD_DBIT 0
Define LCD_RSREG PORTB
Define LCD_RSBIT 4
Define LCD_EREG PORTB
Define LCD_EBIT 5

REM Variables
TMR0_POSTCOUNT1 var WORD ' POSTSCALER COUNTERS
COUNT_RESULT var WORD ' THE RESULT OF THE COUNT
REFRESHED var BIT ' FLAG TO SAY COUNT REFRESHED

'-------------------------'
ON INTERRUPT GOTO PULSE_COUNT ' DEFINE WHERE TO JUMP TO ON AN INTERRUPT
'-------------------------'

GOTO INITIALIZE ' JUMP ALL INT CODE

'----- INTERRUPT CODE -------------------
Disable
PULSE_COUNT:
TMR0 = TMR0 + 7 ' RELOAD THE TIMER
TMR0_POSTCOUNT1 = TMR0_POSTCOUNT1 - 1
IF TMR0_POSTCOUNT1 = 0 THEN
TMR0_POSTCOUNT1 = 500 ' 1/4 sec (may need some adjust)
T1CON.0 = 0 ' TURN OFF THE TMR1
COUNT_RESULT.lowbyte = TMR1L ' GET THE COUNT
COUNT_RESULT.Highbyte = TMR1H ' GET THE COUNT
TMR1L = 0
TMR1H = 0
T1CON.0 = 1
REFRESHED = 1 ' SET FLAG TO SAY COUNT READ
ENDIF
INTCON.2 = 0 ' CLEAR INTTERUPT FLAG
Resume
enable ' RELOAD THE SYSTEM VARS
'------ END OF INTERRUPTS CODE ----------

'------ INTIALIzE ALL REGS --------------
INITIALIZE:

TMR0_POSTCOUNT1 = 500 ' INITIALZE THE POST SCALERS
OPTION_REG.0 = 0 ' SET THE PRESCALER TO 1:1
OPTION_REG.1 = 0
OPTION_REG.2 = 0
OPTION_REG.5 = 0 ' TMR0 CLOCK FROM MAIN OSC
OPTION_REG.3 = 0 ' IN THIS INSTANCE PRESCALER IS ASSINED TO TMR0
INTCON.2 = 0 ' CLEAR INTERRUPT FLAG
T1CON = %00000110
T1CON.0 = 1 ' TURN TIMER 1 ON
TMR0 = 7 ' LOAD THE TIMER
INTCON.5 = 1 ' ENABLE TMR0 INTERRUPTS
REFRESHED = 0 ' DONT MAKE FIRST READ UNTIL MAIN INT HAS OCCURED
INTCON.7 = 1 ' START THE WHOLE THING RUNNING
COUNT_RESULT = 0
pause 500
lcdout $FE,1

'------ MAIN CODE BELOW HERE -------------

LOOP:
IF REFRESHED = 1 THEN
lcdout $fe,1,$fe,2, "Freq = ", dec (COUNT_RESULT * 4) ' Show results in pulses / Sec
REFRESHED = 0 ' PREVENT A RE-READ UNTIL NEXT MAIN INTERRUPT
ENDIF
GOTO LOOP

END

===========================================

Well, I bought a new car (used, but newer than the other one). I had do modify a lot my circuit to make it working due to the Car´s Hall sensor strange bahavior. Now, it´s fixed.

But now, I would like to measure my instat fuel consumption, reading the Injector´s "on" time and the engine´s RPM (please, see http://www.eelkevisser.nl/fuel.htm )

I was reading the 16F877A datasheet and I noticed that CCP1 and CCP2 uses Timer1.

Is it possible to measure those two other parameters (engine´s RPM and Injector "on"-time) using the CCP1 and CCP2 without messing my interrupts ?

Sorry for my bad english !

Regards.

Sérgio
- 19th July 2007, 16:22
Bruce

Capture is not reliable with Timer1 in asynchronous counter mode. You're also
stopping & clearing Timer1 in your interrupt handler which would cause
problems with capture.

I would change to the 18F4431. This one has a Motion Feedback Module with
capture that uses Timer5, measures pulse widths or frequency, and it's really
easy to use.

The 18F4431 has everything you need.
- 20th July 2007, 04:13
Johan

Hi Bruce,

I am interested to use motion feedback module on 18F4431, could you please post sample code how to read the number of rotation ?

Thanks,

Johan
- 20th July 2007, 12:15
srspinho

Thanks Bruce !

I will check here were I live, if I can buy this device.

But, thank you for your advice !

Do you have tips on how to use the CCP4 and/or CCP5 on this device ?

Regards .

Sérgio
- 20th July 2007, 16:43
Bruce

Here's an example of measuring a 32kHz signal on RA2 with the Motion Feedback Capture. It's pretty simple to use.

Code:

DEFINE OSC 4 DEFINE DEBUG_REG PORTC DEFINE DEBUG_BIT 6 DEFINE DEBUG_BAUD 9600 DEFINE DEBUG_MODE 0 ' 1 = inverted, 0 = true T1 VAR WORD T2 VAR WORD T3 VAR WORD Capture VAR PIR3.1 False CON 0 True CON 1 ' auto time base reset, capture on rising to falling edge RiseToFall CON %01000111 ' auto time base reset, capture on falling to rising edge FallToRise CON %01000110 ' auto time base reset, frequency mode, capture on every rising edge Frequency CON %01000101 ANSEL0 = 0 ' All digital TRISA.2 = 1 ' Cap1 input pin (Capture input) INTCON = 0 ' Interrupts off TMR5H = 0 ' Clear high byte of TMR5 counter TMR5L = 0 ' Clear low byte T5CON = %00000001 ' prescale=1:1, int clock, TMR5=on GOTO Main Trash: ' Trash 1st capture after capture mode changes Capture = False ' Reset capture flag WHILE Capture = False ' Wait for capture WEND ' Capture = False ' Reset capture flag RETURN ' Return Main: GOSUB LtoH GOSUB HtoL GOSUB Freq PAUSE 500 GOTO Main LtoH: ' Capture on falling to rising edge CAP1CON = FallToRise GOSUB Trash WHILE Capture = False WEND T1.HighByte = CAP1BUFH ' high byte T1.LowByte = CAP1BUFL ' low byte DEBUG "Low PW = ",DEC T1,"uS",13,10 RETURN HtoL: ' Capture on rising to falling edge CAP1CON = RiseToFall GOSUB Trash WHILE Capture = False WEND T2.HighByte = CAP1BUFH T2.LowByte = CAP1BUFL DEBUG "High PW = ",DEC T2,"uS",13,10 RETURN Freq: ' Frequency measurement mode, capture every rising edge ' to measure period CAP1CON = Frequency GOSUB Trash WHILE Capture = False WEND T3.HighByte = CAP1BUFH T3.LowByte = CAP1BUFL DEBUG "Freq = 1/",DEC T3,"uS",13,10 RETURN END

Returns;
High PW = 17uS
Low PW = 14uS
Freq = 1/31uS

This 18F series has a boat-load of nifty features. Check out how fast the A/D
is. Should be a killer PIC for robotics applications.
- 20th July 2007, 18:05
srspinho

Thank you very Much Bruce !

regards .

Sérgio
- 11th September 2008, 03:02
mystified

I too am trying to use capture mode with hall sensor on cap1 2 an3

Code:

duty var word ansel0=%00000000 'all digital 'ansel1=%00000000 trisa=%11111111 'set all port a pins to input cap1,cap2,cap3 trisb=%00000000 'set all port b pins as output portb=%00000000 'set port b to all zero trisc = 2 ' rc1=flta input(ground pin 16 to stop) pin 16 high to run 'capture mode intcon =0 'interrupts off tmr5h = 0 'clean high byte of tm5 counter tmr5l = 0 'clean low byte t5con = %00000001 ' prescale 1:1, int clock, tmr5 =on cap1con=%01000101 ' enable caputure,pulse width measurement mode, 'every rising o falling edge cap2con=%01000101 cap3con=%01000101 where is the capture data go from here ' ovdcond=%00010010 'turn on / off pwm pins 'ovdcons=%00000000 'pcpwm init dtcon = %00000101 'set deadtime to -500ns ptcon0 =%00000000 ' 1:1 postscaale,fosc/4 1:1 prescale, free run mode ptperl =0 ptperh=1 pwmcon0= %01010000 'pwm[5:0] output enabled 0100pwm4,5 independent, 'pwm0,1,2,3 complementary pwmcon1=1 'update enable,overrides sync w/time ptcon1=%10000000 'pwm time base is on, counts up fltconfig = %00000011 ' enable fault a, cycle-by-cycle mode duty =100 ' 50% =800 PDC2L = duty.lowbyte 'main a fixed 50% duty cycle on pwm4,5 PDC2H = duty.highbyte 'independent pwm outputs. main: for duty = 900 to 100 step-1 ' 10% to 90% PDC0L = duty.lowbyte 'register controls pwm1/0 PDC0H = duty.highbyte PDC1L = duty.lowbyte 'register controls pwm3/2 PDC1H = duty.highbyte PDC3L = duty.lowbyte 'register controls pwm6/7 PDC3H = duty.highbyte pause 50 next duty pause 500' 1/2 second delay between ramp up / down for duty = 100 to 900 ' 90% to 10% PDC0L = duty.lowbyte PDC0H = duty.highbyte PDC1L = duty.lowbyte PDC1H = duty.highbyte PDC3L = duty.lowbyte PDC3H = duty.highbyte pause 5 next duty pause 500' 1/2 second delay between ramp up / down goto main end
- 11th September 2008, 03:37
skimask

Instant Fuel Consumption

Here's how I monitor instant fuel consumption...

http://www.youtube.com/watch?v=7sUVMn4OJ58
- 19th September 2008, 11:58
mystified

hall senors

trying to us motion feedback module with capture on state mode on pins 3,4,5
- 19th September 2008, 12:49
skimask

Quote:

Originally Posted by mystified

trying to us motion feedback module with capture on state mode on pins 3,4,5

What's the question/problem?
- 20th September 2008, 03:19
mystified

brushless motor control

i want to set up a brushless dc motor control,I need to setup capxcon to input state change, (hall sensor as the inputs)
rest tmr5 if a change on cap1 or cap2 or cap3, us a ic interupst and ovdcond regisiters to turn on or off pwn channels (pins)in a sequence for rotation for the motor. How do I check the flags to turn on or off the channels ?(doc an899)
- 20th September 2008, 08:35
Archangel

Quote:

Originally Posted by skimask

Here's how I monitor instant fuel consumption...

http://www.youtube.com/watch?v=7sUVMn4OJ58

Looks great Jeremy, more on screen than my snap on scanner, what kind of display is that, a monitor? What are you measuring the fuel flow with? ( the mpg goes over 60 due to the computer shuts off the fuel completely when decellerating. Impressive work.
- 20th September 2008, 15:50
skimask

Quote:

Originally Posted by Joe S.

Looks great Jeremy, more on screen than my snap on scanner, what kind of display is that, a monitor?

http://www.sparkfun.com/commerce/pro...roducts_id=569
It's the same screen that I posted the color lcd code to here awhile back.

Quote:

What are you measuring the fuel flow with? ( the mpg goes over 60 due to the computer shuts off the fuel completely when decellerating. Impressive work.

Straight OBD2 data, mass air, temp, pressures, etc.etc.etc. Do enough math, mainly unit conversions and a bit of integration, and you can get almost anything you want out of OBD2...although the outputs are all 'estimated' because they're all derived from formulas with a few generic numbers (i.e. fudge factors) thrown in. But based on my driving over the past 8,000-ish miles, that 'estimation' seems to be quite accurate.
And when the mileage goes over 60...
The Nissan I've got ('98 200SX) isn't very aggressive at decel fuel cutoff like todays vehicles are. Based on my datalogging and calculations, if I'm doing 65mph and I let off the gas, I only get complete cutoff under certain conditions (above 2000 rpm, above 25mph, closed throttle, MAF below 500grams/sesc, MAP below 6 in/hg, calc.load.val below 10%). Other than that, I figure it goes open loop and tries to hit an A/F of about 25:1. Apparently, today's vehicles go to decel cutoff as soon as you think about slowing down (which accounts for some of todays vehicles being a just a little bit jerky at lower throttle settings in my experience).