16f18877 internal Zero Cross Detector

[chipfryer27]

Hi

Maybe not quite what you are after but you can reference pins directly, for example in a decision

Screenshot 2026-02-12 214622.jpg (87.23 KiB) Viewed 3093 times

Regards

[mnfisher]

Possibly!

I suspect you might be able to do $PORTA0 = 1 in a calculation too?

Though - this is new to me - and I've not tried it...

[chipfryer27]

Hi

You can indeed reference ports/pins in calculations.

This calculation immediately turns on the inbuilt LED on a lolin-lite (pin 22, active low)

Screenshot 2026-02-13 051633.jpg (48.19 KiB) Viewed 3065 times

Regards

[alanwms]

See below

[alanwms]

Maybe an easier method would be to simply connect a dual optical isolator via resistor directly to the micro controller transformer on the secondary ac side. Your open collector outputs will switch at every zero crossing.
That signal is connected to the hardware interrupt which services the routine.
If you need schematic help, I do have a working example.
Send me a note at aw@machineautomationproducts.net