Hello! I work with STM32F429 nucleo board. I try to connect it to CC1125 by SPI. The requirement of SCK rise time is less than 40ns. I tried different SPI channels and SCK pins. Typical SCK rise time of the board is about 50 ns. How can I improve it?

[berendi]

Set the GPIO OSPEEDR register bits for the SPI pins.

See Table 58. I/O AC characteristics in the datasheet for possible values, and the description of GPIO port output speed register (GPIOx_OSPEEDR) in the reference manual.

[Tesla DeLorean]

50ns?

What kind of capacitive loading do you have on the pin? What are the speed/slew-rate setting, Show Code

What kind of scope probe are you using? Use a 10X probe, and a fast scope