Add support for W55RP20-EVB-Pico and WIZNET_PIO_SPI communication.

[wizhannah]

The W55RP20-EVB-Pico is an evaluation board for the W55RP20, a SiP (System in Package) chip that integrates the W5500 (wired TCP/IP controller) and the RP2040. As a result, both the features of the Raspberry Pi Pico and the W5500 can be utilized.

The W55RP20 features two identical PIO (Programmable Input/Output) blocks, one of which is used for communication with the W5500. For more detailed information on PIO, please refer to section 3 "PIO" in the RP2040 datasheet.

This PR adds initial support for the W55RP20-EVB-Pico board. The changes included in this PR are as follows:

1. Added support for W55RP20-EVB-Pico under ports/raspberrypi/boards/
2. Implemented WIZNET_PIO_SPI in both:
   • common-hal/busio/
   • shared-bindings/busio/
3. New files were created in the ports/raspberrypi/wiznet_pio_spi directory:
   • wiznet_pio_spi.c
   • wiznet_pio_spi.h
   • wiznet_pio_spi.pio

The wiznet5k_simpleserver example ran without any issues:

import board
import busio
import digitalio

import adafruit_wiznet5k.adafruit_wiznet5k_socketpool as socketpool
from adafruit_wiznet5k.adafruit_wiznet5k import WIZNET5K

print("Wiznet5k SimpleServer Test")

# For Adafruit Ethernet FeatherWing
cs = digitalio.DigitalInOut(board.W5K_CS)

spi_bus = busio.WIZNET_PIO_SPI(board.W5K_SCK, MOSI=board.W5K_MOSI, MISO=board.W5K_MISO)

# Initialize ethernet interface
eth = WIZNET5K(spi_bus, cs, is_dhcp=True)

# Initialize a socket for our server
pool = socketpool.SocketPool(eth)
server = pool.socket()  
server_ip = eth.pretty_ip(eth.ip_address)  
server_port = 50007 
server.bind((server_ip, server_port)) 
server.listen() 

while True:
    print(f"Accepting connections on {server_ip}:{server_port}")
    conn, addr = server.accept()
    print(f"Connection accepted from {addr}, reading exactly 1024 bytes from client")
    with conn:
        data = conn.recv(1024)
        if data:
            print(data)
            conn.send(data)
    print("Connection closed")

Additionally, the following examples were also tested and passed successfully:

• Adafruit IO (DownLink, UpLink, Up&DownLink)
• DHCP
• DNS
• HTTP (Webclient, Webserver)
• Loopback
• MQTT
• SNTP

[dhalbert]

Thanks for adding these new boards.

We don't put board- or port-specific stuff in shared-bindings. The idea of shared-bindings is that the Python API is common across all the ports that implement it.

Instead, put the port-specific stuff in ports/raspberrypi/bindings. There are already some RP2xxx-specific things there, which you can use as models.

In this case, it would make sense to create a new module, called, say piospi with a class piospi.SPI(). The you can have a flag, say, CIRCUITPY_PIOSPI, which would be enabled only for these boards.

I am not sure if this is true, but is it the case that this PIO implementation is not limited to Wiznet boards? Could it be used on any PIO-capable RP2 board? That is why I suggested the name above. Internally, you can then drop the "wiznet" part of the names, and just use 'piospi`.

We could also consider naming the top-level module piobusio. for right now only includes SPI, but could include PIO-based I2C or UART in the future.

How does this all sound to you?