Using CCP1 and CCP2 to measure instant fuel consumption

[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

[Bruce]

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

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.

[srspinho]

Thank you very Much Bruce !

regards .

Sérgio

[mystified]

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

[skimask]

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

[mystified]

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

[skimask]

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

What's the question/problem?

[Archangel]

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

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.

[skimask]

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.

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).