On the  Pico-ice the USB talks to the RP2040, which talks to the Ice40 FPGA.  This is called a pass through.  It works in C, but needs to be implemented in other languages on the RP2040, such as ZeptoForth and MicroPyhon.  To implement it and debug it, one needs an echo server running on the FPGA.  

This echo server flashes green every 3 seconds.  This is so that you know that it is installed correctly.  When you send text to the echo server, it  flashes white, once for each character typed,  and is echoed back.  Best to type text in between the green flashes.

The gateware beta version is available on the discord server.
To flash the gateware first install dfu-util

dfu-util -a 1 -D hardware.bin

To talk to the FPGA, use picocom.

First you have to find the usb devices.  On Mac OS X I did

ls /dev | grep usb

and chose the second tty

picocom --omap crcrlf /dev/tty.usbmodem103

The omap option converts the keyboard carriage return into a carriage return and line feed.

So far, I am the only person who has used it.  So to make sure it works correctly for you, first test it using the most recent RP2040 firmware, then use it with whatever language you are developing for.

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