SPI interface The ESP32 does all the hard work of connection to the WiFi network and handling TCP/IP sockets, it is just necessary to send the appropriate commands over the SPI link. In addition to the usual clock, data and chip-select lines, there is a ‘reset’ signal from the Pico to the ESP, and a ‘ready’ signal back from the ESP to the Pico. This is necessary because the Pico spends much of its time waiting for the ESP to complete a command; instead of continually polling for a result, the Pico can wait until ‘ready’ is signalled then fetch the data.

My server code uses the I/O pins defined by the Adafruit Pico Wireless Pack: