Instant Interrupts - Revisited

[srspinho]

Hi Darrel,

some days ago, I was trying to measure the "ON time" of my car´s gasoline injectors (one of the 4)

I´m using a 16F877 @ 10 Mhz, and I´m using the Timer0 as a 250 ms counter and Timer1 as a pulse counter, I ran out of possibilities of new measurements.

Bruce told me that I should use a new device with more timers available, like the 18F4431 (or similar).
The problem is : This device (or similar) is not available here in Brazil, and Microchip do not send samples to Brazil.

I was reading this post about the interrupts and decided to ask :

Is that possible to read the pulses on Timer1 on a fixed time interval (so, I would have the car´s speed and the mileage) and measure the injector on-time (so I would have the consumption) with the instat interrupts running on a 16f877 ?

Thanks !

Sergio

[Darrel Taylor]

Sure you can.

I'd use the Capture mode of the CCP modules using Timer1, for the ON time.

Timer 2 can be the timebase used to count the speedometer pulses on the INT (external interrupt) pin.

And the same signal from the Injector can be fed to T0CKI, so Timer 0 can count the RPM's too.

Speed, Distance, Consumption and Tachometer.
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[srspinho]

Wow !

thank you !

I´ll try it this weekend and post the results here !

Bye !

[Bayliner]

Hi,

how i use the instant interrupt (very nice pice of code) and the write or eeprom comand. In the manual they say to turn off all interrupts. Or is there no problem to use them together?

Many Thx for reply

[Darrel Taylor]

If an interrupt happens at just the right time, or actually just the Wrong time, it can cause the EEPROM write operation to fail.

But it's not always necessary to turn off the interrupts.

What I do, is write the value to EEPROM, then read it back and compare it to what it was writing. If they're not the same, go back and try to write it again.

After a certain number of tries (I use 10, but it never takes that much), if it still hasn't written it properly, then turn off the interrupts and write it one last time.

It takes a little extra code, and some extra time, but it doesn't mess with the interrupts.

HTH,

[Acetronics2]

Hi, Darrel

I'm playing with PbP Interrupts ( a Lawn tractor computer: Total run Time, Split time, RPM, max RPM, Air and Oil Temp and Oil press ... AND a maintenance reminder)

... AND ...

I did not see an INT_DISABLE GLOBAL and INT_ENABLE GLOBAL Macros ... just for the compatibility with the others "interrupt control" macros ...

Of course just to set "THE" INTCON.7 bit ... ( case is i.e.... using the asm "sleep" instruction !!! )

No, no thats not to be called lazyness ...

Nice playing ground ... Thank you once more !!!

Alain

[Darrel Taylor]

Hi Alain,

You are absolutely correct.
To keep everything consistant, there should be a GLOBAL for the INT_ENABLE/DISABLE.

I will include that in the next version, which should be available very soon.

Thanks for the idea's.
Wish I received more of them.
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