question about crystal oscillator pcb?!

[JonSea]

I have never used a PIC18F or PIC16F where 22pF did not provide satisfactory results. Nor have I ever had any issues with an oscillator failing to work on PICs, whether ground be connected to the outside pins of the caps or the inside. I think maybe the reality of the situation is drowning in minutia.

 

[emb]

I have never used a PIC18F or PIC16F where 22pF did not provide satisfactory results. Nor have I ever had any issues with an oscillator failing to work on PICs, whether ground be connected to the outside pins of the caps or the inside. I think maybe the reality of the situation is drowning in minutia.

Thank you

 

[emb]

A recommended capacitor size is usually in the specifications for the crystal. If not, assume it is in the 10 pF to 47 pF range. Too much capacitance will overdrive the crystal (also mentioned above). Measuring the actual frequency can be difficult. If you have a good HF receiver, you might pick up the frequency with a small antenna nearby.

What I have done recently is use TMR1 as a frequency counter and a calibrated source. I then changed the crystal/resonator capacitor for the MCU slightly to tune it. Crystal tolerance was specified as +/- 0.5%. I wanted it to be closer. For most cases, changing that will not be necessary.

Here's a more detailed discussion: https://blog.adafruit.com/2012/01/24/choosing-the-right-crystal-and-caps-for-your-design/

thank you for your helpful comment

i will print the board soon ..
and i will post any problems here

thanks all for your appreciated effort ^_^