STM32 Configuring Clocks using STM32CubeMX

Why is clock configuration important?

Performance & Power Consumption: STM32s can run at various clock speeds. To put it real simple, faster clock speeds allow for faster code execution, but at the cost of higher power consumption.
Peripheral Functionality: Many peripherals (ie: UART, SPI and I2C) require specific clock frequencies to function correctly.
Optimized Power Modes: Different clock configurations are required for entering/exiting low-power modes, ensuring efficient energy usage when the MCU is idle.
Stability: Incorrect clock settings can make the microcontroller unstable or non-functional.

.ioc Configuration

Navigate to the Clock Configurations tab located near the top of the window
- Within the clock tab, the flow chart runs left to right, going from source to peripheral / source
- Across the entire flowchart you will see boxes representing clock values and prescalers
  - Clock values with units in round brackets ()
  - Prescalers which act as multipliers and dividers are denoted by X and / respectively
Set the clock source via the PLL Source Mux
- The typical clock sources are HSE, HSI, LSE or LSI
  - External, internal, high-frequency or low-frequency oscillators
- Most STM32s will have an internal oscillator (HSI or LSI), but for precision tasks, you might have an external crystal (HSE or LSE)
Configure the PLL (Phase-Locked Loop)
- The PPL is a circuit that can multiply the oscillator frequency
- The PPL is typically the main prescaler that precedes all other prescalers and peripherals
  - For example, if you have an 8 MHz external crystal, and you want your microcontroller to run at 72 MHz, you'd use the PLL to multiply the 8 MHz by X 9
Resolving clock issues
- If any boxes turn pink / red, this means improper clock configuration is detected
- You can manually fix the flagged boxes, you can also click on the "Resolve Clock Issues" box to try CubeMX will automatically try fixing the issue