SOLVED: Post #11 - IOC on negative edge sometimes triggers twice on single press

[tumbleweed]

just a comment...

If you look at your code in post #1, the only thing the ISR does is set a flag that's read in your mainline code (NAV2_Swap_ON = 1).
You could drop all the interrupt stuff and just poll the IOCIF flag (or the individual flag bit) in the main loop with the same effect, much as Richard's done.

The interrupt flag bits get set even if interrupts aren't enabled.

[HenrikOlsson]

Yes!
Quite often I see comments like don't do any work in the ISR, just set a flag and do the work in the main loop.

That's totally fine if what the ISR is doing is, for example, putting UART characters into a buffer and when CR is received sets a flag. When the main loop sees that flag it processes the message.

But simply setting a flag that there's been an interrupt and then poll that flag in the main loop is...well of not much use and a waste resources. Just poll the interrupt flag (and remember to reset it) instead.

In general, the ISR should be kepts short and tight (no blocking commands like PAUSE etc (again, in general)) but if you're not actually DOING anytning in the ISR then you might not need an interrupt to begin with.

Sorry for the rant ;-)

[Demon]

...But simply setting a flag that there's been an interrupt and then poll that flag in the main loop is...well of not much use and a waste resources. Just poll the interrupt flag (and remember to reset it) instead....

It's not a rant if you guys help me. I didn't know that about the IOC flag being set regardless (I've done a lot of reading on Interrupt - remembering what I read is something else entirely).

Richard did find the real problem. I was using 0.01uF for the encoder and the switch. This is what it looked like at higher resolution:




Then I changed for 0.1uF:



Just a blip on this one:




But I have to use 0.01uF on the encoder or else they don't act properly.


So now I have to decide if I keep the 16F18877 and poll the IOC flag, or go back to the 16F1937 and poll the Port pin. I'm leaning towards the 16F1937 cause it costs a bit less.

[Demon]

Turns out I don't really have a choice to stay with the 16F18877:

- 16F1937 has TTL General Purpose pins.
- 16F18877 has TTL and ST General Purpose pins.

74HC14 only costs $0.09 at JLCPCB, but there's other costs associated with assembly, as well as lost real-estate on the PCB:
https://jlcpcb.com/parts/componentSe...archTxt=C97666

[tumbleweed]

- 16F1937 has TTL General Purpose pins.
- 16F18877 has TTL and ST General Purpose pins.

You should be able to set the pin type in the 16F18877 to either ST or TTL to match the 1937 type if that's what you're after.
I don't think your 'INLVLB = %00000100' statement changed anything for RB2... it's still the default setting.