Hello again I just wanted to close this issue with an autoreply, in order to leave some useful data and share with other people who may experiment a similar problem.
I can’t ask the PlatformIO Community to have enough time to examine my code, so I found the solution by myself. As I am new to this line of processors, I am getting the skills to “know” the machine in a more deeper view.
As I have many years as a programmer and hardware designer, and as the small, simple blink program worked fine and also could be debugged, I must say that I skipped a terribly important fact that produced the problem. My goal was to have some “popular” STM32F103C8T6 interfaces working in the form of .c working modules. This includes SysTick event with a timer module for a “custom” delay_ms() function, and the chance to run some tasks on the same 1ms tick, keyboard, multiplexed LED display, etc.
Also serial asynchronous communications, SPI, and ADC. I am really porting very simple working modules coming from Freescale, Atmel and some other families. My uploaded software has all these features working fine as expected. The other goal is to avoid using HAL as much as possible to reduce overhead.
For the ADC, I picked a YouTube video example using continuous conversion of 4 channels with DMA that use DMA interrupts. This was my fatal error, not considering that a 72MHz clock CPU was continuously converting and ADC/DMA interrupting and storing values in a RAM array at a rate so high that made the ADC/DMA combination not to ever return to the main loop. This happening in the megahertz region !
The solution was to go down to a more simple and conventional code, triggering ADC without DMA conversions as needed in a loop or even inside the SysTick handler call, along with other mentioned useful simple services.
Once fixed the ADC/DMA problem, the program returned to normal and the debugger began to work perfectly in all its features.
I recommend all STM32 newbies to take care with DMA interrupt rates in continuous processes such as ADC conversion with 1.5us conversion time, even with many samples per channel. I am NOT saying not to use DMA, which is such a powerful feature. Just take care at the rate at which interrupts events occur.
So I will report this post as problem SOLVED. However, there is still a detail that I need to resolve concerning that in both PlatformIO installations that I regularly use in separate Windows 10 Pro machines, the light blue status bar at the bottom of the screen remains light blue instead of changing to orange when switching to debug mode. But I will consult if I may open a different post for this issue.
Thank you all for your time and advice !