Cap Sense ...getting a drowsy PIC to wake out of sleep!!

[HankMcSpank]

Ooh, now I see what you are doing. I got this CSM working with a 16F727 and other chips but not in sleep mode. It is good to know that it works in sleep mode. Don't you have inaccurate value readings with the WDT as the timeframe interrupt? I read somewhere that the WDT is not too accurate.

The readings only waiver by about 1%....a finger press see the deviation something like 80% ...plenty of headroom there!.

Also, you said that you are using WDT intervals of two seconds. I didn't know you could go that high. I guess that a quick touch is not going to be detected by your device. I have used intervals in the order of a few milliseconds.

According to the datasheet, the 16f1824 can have a WDT period of 256 seconds....but that'd be impossible to use with capacitive touch & sleep (timer1 would always overflow while asleep, as it's not possible to set the CSM output frequency low enough to avoid a timer1 overflow for 256 seconds!).

You are correct about quick tap not working when the WDT period is 2 seconds ...so, I'm using two sleep periods.

My first sleep period is only about 64ms ...that's very responsive to quick taps. Then after no finger taps detected for over 60 minutes, I actually then extend the sleep period out to about 2 seconds.......& yes, that requires you to hold you finger on the sensor for about two seconds... however once it comes out of sleep in this mode, I put the the WDT back to about 64ms.

the reasoning behind this, is that when a user first turns the circuit on, he'll have to hold his finger on the sensor for 2 seconds...but from thereon, it'll be responsive/snappy .....then if he stops using the circuit, it'll go into longer sleeps to conserve battery power.