Hi Charles,

noise suppression and debouncing are easy tasks for any micro. So its pure waste to use 2 additional circuits instead of some code lines.


Hi Simon,

maybe I must declare it more.
My suggestion was also to suppress noise:
In Germany the ring signal was a 25Hz 60V AC signal of 1s duration. It was repeated every 10s.
So you get 25 pulses = 25 edge triggered interrupts on every burst.
If the burst start in the middle of the 1s clock, you can then count 12 pulses and the remaining 13 pulses in the next second. E.g. on using a threshold of 8, these 12 counts are detected as ring and all counts below 8 as noise.

A second counter count these detections of ring and can do some actions.
Also the 1s clock can be used to detect the stop of ringing. Since the ring was repeated every 10s, a time interval of e.g. 15s can be used to detect, the caller has hang up and reset the ring counter.


Peter