How can I measure Duty cycle ?

[ardhuru]

which is why I said to use the pulsin commands in the earlier post.

I'm afraid this does not work; after the first pulsin has taken its reading, since the transition has *already* happenned, the next pulsin of the opposite polarity (level?) will take place only at the next-to-next pulse. Of course, if the duty cycle for a sequence is going to stay somewhat the same then this should make no difference. I was trying to decode an IR signal by using these consecutive pulsins, and got completelty wrong results.

[sougata]

Hi,

I am not sure about the fuel injection stuff. Possibly a variable duty and variable frequency. One option may be to use the portb on change interrupt feature. So for every falling or rising edge you get an interrupt. One problem is that depending on the timer prescaler you may run out of time if the frequency is too low causing a timer overflow. Again that can be accounted with ISR checking for timer overflow and incrementing a pseudo timer high byte counter making the timer a 16bit one.

[Acetronics2]

Hi,Sougata,

you're right ...

But the big problem is injectors are nor open 100% of the cycle !!!

a "100%" aperture equals, say, only 20 or 30 degrees at crankshaft ....

and this value has to be entered somewhere to measure something useful.

now, a simple "PULSIN" is enough to measure the ON duration in µs ... but maximal aperture ( vs. rotation speed ? ) has to be known to calculate a displayable percentage.

add to that needles inertia is not negligible at those timings ... and you'll see your measure is somewhat false !!!

Some data is missing here ...

Alain