Nigel Goodwin said:
The whole idea of this is to get reliable SQUARE pulses entering the PIC, by adding such a low frequency low-pass filter you will be making the drive nearer a sinewave than a square wave.
So dump the capacitor!, also dump the two diodes, they aren't required, the PIC already has them internally - see figure 5.4 of the 16F628 datasheet.
Nigel,
Thanks for response. But if you look at my Figure 3, it is being presented with a squarewave but will not work. The only config that does work reliably is Figure 2 - a non square wave. ?? I know the PIC has internal diodes, but I was once told by an IC researcher (admittedly a few decades ago) that the internal diodes are sometimes not adequate.
The PIC data sheet for the 16F84 states that RA4 has an internal Schmitt Trigger, so it sould work on slow waveforms - as we found. My main question is - why is it having a problem with the square wave as per fig 3?