Instant Interrupts - Revisited

[Darrel Taylor]

Ioannis,

On those chips, the IOCIF bit is read-only and only gets cleared when ALL of the IOCBF flags are clear.
So you can set the INT_Handler's ResetFlag option to NO.

Then be sure the IOCBF flags are cleared before exiting the ISR.
Also, take a look at section 13.4 in the datasheet regarding clearing the flags.

[Ioannis]

Excellent! Works terrific now.

These chips are a little pain in setting them.

Thanks Darrel.

Ioannis

[aratti]

Use the code in post#27, (new approch to rotary encoder) is more efficient and you can achieve even higher frequency.

Cheers

Al.

[Ioannis]

Hi Al. I am using the #27 ISR.

The thing that I added was the check for the 4 counts before Q_Count variable is incremented or decremented.

Thats because the encoder I use produces 4 pulses on every step I turn the knob. Thanks Henrik for noting this.

Ioannis

[aratti]

The code was written to read quadrature count. Any rotary encoder with two channels will generate quadrature count.

Al.

[Ioannis]

Yes that is correct. So the Q_count variable is incrementing by 4.

Ioannis

[AvionicsMaster1]

If this topic was previously mentioned, I apologize for not finding it.

I'm using a 16F877A with a 4 MHz crystal and two 22pf caps with a LED hooked up to portb.1 and the code from example 2 of DT_ints-14.bas on DTs site. I'm using a oscope to look at the timing of the LED flashes and they are occuring around 950msec apart.

My question is, is there a way to tune the oscillator or modify DT interrupts to get it closer to a true 1 second pulse time? I know it's not far off but I was trying to learn something and maybe make it more accurate at the same time. Your help would be appreciated.

Yes I did read the datasheet but I couldn't find anything like OSC tune that I've seen for the 12F683.