Does the Nucleo-H743ZI slows down after power off ?

[LuizLS]

I am leaning to program the H743ZI and have a simple application where the user leds blink at a certain rate given by a delay produced by a for loop.

When the code is uploaded, I get the desired rate. If I disconnect and connect the board again, the program still runs, but at a slower LED blink rate. If I upload the code again, all is back to normal.

[Tesla DeLorean · Accepted solution]

Probably an issue with selecting clock source, or PLL.

Try using HSI as source

[LuizLS]

Following your comment, I wrote a code to read the system clock source (from the RCC_CFGR register) and blink the user LED with the result.

Right after the code upload, PLL1 is selected as system clock. Turning the board OFF and ON again, the slower HSI is selected.

After some trials, I found out the problem is somehow related to how the STM32 System Workbench interacts with the Nucleo-H743ZI board. If the code is uploaded with the option "Reset after programming" selected, the system clock PLL1 is selected. If I leave the option out, and reset manually, HSI is selected.

It could be related to the ST-Link debugger on the board.

Thanks Clive, that was very helpful.