rxstate | Simple opinionated state management library based on RxJS | Reactive Programming library

I tried following Allen Denver's article to implement asynchronous serial port I/O. What isn't mentioned in the article is how or where to call the functions in a main program loop in a useful manner. After putting them in a loop that comes back every second, it was clear there should be no need to call the ReadFile() periodically. I tried putting a WaitCommEvent() in the loop so the read would only occur if characters arrived at the port. That caused a cascade of errors. In trying to simplify the code into something I could post here, even my attempts to open the file in OVERLAPPED mode started failing, so I can't seem to post a useful example. However, I will post something similar with the basic notion that I don't really care if the reads and writes have to be synchronous if I can simply trigger them with an asynchronous event like characters showing up on the serial port. The asynchronous functions from Allen Denver's article are quite involved, and it's not clear to me from his examples how to trigger a read on characters arriving at the port.

In the following code there are five lines commented out in the body of the while(1) loop where I was trying to wait for the characters to arrive. The WaitCommEvent() errors appeared to cite pending I/O even though the port was opened in overlap mode (in the original code), and both the send and receive functions had their own OVERLAPPED structures. What is the proper way to resolve this?

I'm following the advice:

It is possible to achieve your own composite USB Device, by combining the desired classes' drivers into one class, under your own folder within: Middlewares\ST\STM32_USB Device Library\Class

from https://community.st.com/s/question/0D50X00009XkgYtSAJ/stm32f4-hal-composite-usb-device-example

I now have a unified configuration descriptor.