Arduino for STM32

Thanks for that.
Yes, the total code is quite large and worked perfectly for years.

As a bit different test, this shows a USB buffer size of 64 bytes max, but prints about 128 before losing it. The string variable teststr can go long if hardcoded:

else if (cmmd == 'c') {
while (Serial.available() == 0) {}
Serial.print("string started ");
Serial.println(Serial.available ...

I started (as a non programmer) with Thomas Roell and the Ladybug board. I used his board files and library forever.
Now Im porting to the STM32duino Core. Got through most porting issues with Generic L432KCUx series setting. But I used to write from a PC to my board through USB a large chunk of ...