How to write a time difference function to STM32F4

i am working on STM32F4 and pretty new at it. I know basics of C but with more than 1 day research, i still not found a solution of this.

I simply want to make a delay function myself, processor runs at 168MHz ( HCLK ). So my intuition says that it produces 168x10^6 clock cycles at each seconds. So the method should be something like that,

1-Store current clock count to a variable

2-Time diff = ( clock value at any time - stored starting clock value ) / 168000000

This flow should give me time difference in terms of seconds and then i can use it to convert whatever i want.

But, unfortunately, despite it seems so easy, I just cant implement any methods to MCU.

I tried time.h but it did not work properly. For ex, clock() gave same result over and over, and time( the one returns seconds since 1970 ) gave hexadecimal 0xFFFFFFFF ( -1, I guess means error ) .

Thanks.

Edit : While writing i assumed that some func like clock() will return total clock count since the start of program flow, but now i think after 4Billion/168Million secs it will overflow uint32_t size. I am really confused.

The answer depends on the required precision and intervals.

For shorter intervals with sub-microsecond precision there is a cycle counter. Your suspicion is correct, it would overflow after 2³²/168*10⁶ ~ 25.5 seconds.

For longer intervals there are timers that can be prescaled to support any possible subdivision of the 168 MHz clock. The most commonly used setup is the SysTick timer set to generate an interrupt at 1 kHz frequency, which increments a software counter. Reading this counter would give the number of milliseconds elapsed since startup. As it is usually a 32 bit counter, it would overflow after 49.7 days. The HAL library sets SysTick up this way, the counter can then be queried using the HAL_GetTick() function.

For even longer or more specialized timing requirements you can use the RTC peripheral which keeps calendar time, or the TIM peripherals (basic, general and advanced timers), these have their own prescalers, and they can be arranged in a master-slave setup to give almost arbitrary precision and intervals.