Thanks for getting back to me.  Presumably I can use the UART cable from the F401x instead of USB to connect.  Can you confirm whether the project is complete as the status symbol shows it is incomplete?

It works for me. From my point of view it will be "complete" when I've got an SSH or secure telnet client running on an ESP8266, but that's not something it sounds like you need.

Are you planning to publish the code and flesh out both a circuit diagram and some instructions so other users can build it?

All the code is published on github at https://github.com/ncrawforth/VT2040

Could this be used instead of using Linux with minicom to talk to a serial port device such as an ST Micro Nucleo board and get messages? STM has just released an evaluation board to control digital i/o using the fsm01 together with the nucleo F401x board. It can be accessed programatically via  UART (which STM calls USB serial.)

The RP2040 pins are 3.3V, so if the serial port you want to talk to is 5V you'd need a level shifter. Other than that, yeah, it does what minicom does.

meybe You can run https://www.fuzix.org/ on this? how long this device work in real situations? a week, month?

This is a terminal for accessing another device. I use it with ESP-01s, and I think it might be possible to get Fuzix working on an ESP-01, but you can use any device with a serial port.

I get up to 18 hours (less if I'm using wifi) out of good-quality AA batteries.

In my opinion, the key issue is electricity. Fuzix will work on very weak equipment. But no one has made a mobile computer yet.

I am writing this as a person who is looking for such a small computer that would work for a week or a month. does not need much beyond a normal system.