[STM32H503] SPI1 does not send anything

[fpistm]

Discussed in https://github.com/orgs/stm32duino/discussions/2595

^{Originally posted by smalcom December 9, 2024}
Good day, everyone.

I'm trying to launch SPI1 under Arduino IDE. The transmission didn't work and I switched to direct control of the registers.

The problem is solved. By default, stm32duino sets the system clocking from PLL1P. And SPI1 cannot use this signal as a source. I switched SPI1 to clocking from PER_CK and everything worked.

Copy of the stthread