How to use PWM as W5x00 clock

Story

From schematic we know that W55RP20-EVB-PICO have two crystal, 12MHz for RP2040 and 25MHz for W5500 chip.

https://docs.wiznet.io/Product/ioNIC/W55RP20/w55rp20-evb-pico#schematic

This project is target to remove 25MHz and use RP2040 PWM output 25MHz as W5500 clock.

Hardware

W55RP20-EVB-PICO

Software

micropython
hercules 

Thonny

Build

First I find out Y1 25MHz on board and with PCB file on github  I identify W55-XI pin.

Remove Y1 and solder 1K ohm connect board pin19(GP14) and W55-XI pin.

Code

Since I remove w5500 clock, it no longer works properly. It must be given clock during initialization, use below code to output PWM.

from machine import PWM #PWM module

#W5x00 chip init
def w5x00_init():
    PWM(14,freq=25000000,duty_ns=20) #make PWM as w5x00 clock
    
    spi = WIZNET_PIO_SPI(baudrate=31_250_000, mosi=Pin(23),miso=Pin(22),sck=Pin(21)) #W55RP20 PIO_SPI
    nic = network.WIZNET5K(spi,Pin(20),Pin(25)) #spi,cs,reset pin
    nic.active(True)
    

Measure PWM pin signal.

Run example Loopback, it work good as use Y1. 

Conclusion

I make a simple project it can reduce the BOM cost. But the reliability requires longer testing.