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I have a few basic questions about providing a "stable external frequency source" as recommended by "Hardware design with RP2040".

I would just copy the schematic from section 2.3, but JLCPCB does not have the ABLS-12.000MHZ-B4-T crystal in stock, so I'm looking for alternatives.

  1. The only 12MHz crystal JLCPCB lists as "basic part" (no extra fee) is the Yangxing Tech X322512MSB4SI. How large would the resistor in series and the load capacitors have to be for this one?
  2. I have found the Murata CSTCE12M0G55-R0 ceramic resonator with integrated load capacitors. It seems suitable (12 MHz; I want to stay compatible with firmware written for the Pico,) but I am uncertain if I can directly connect the part to XIN and XOUT, or if I need a resistor in series to prevent damaging it. The application notes for the part show input and output being directly connected to such pins on other ICs.
  3. Are input and output pads interchangeable on crystals and resonators?

Context:

  • I don't use USB, so I guess I don't need to be too worried about the stability of the frequency, but I do use the ADCs, PWM slices, and debug pins.
  • I would like to keep the number of components to a minimum, which makes solutions without additional load capacitors and resistors attractive.

TLDR:

  • Can I use the Murata CSTCE12M0G55-R0 as a frequency source and how do I connect it?
  • How would I connect the Yangxing Tech X322512MSB4SI?
Jens
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cg_f
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  • Any solution to this? I already ordered my PCB with XIN and XOUT directly connected to the RP2040. Only now I found out it might not be this easy. Can I just get around with using an oscillator rather than a crystal? – Bastian Springer Jul 21 '23 at 00:25

0 Answers0