Timer updates only after i set a breakpoint

[Hesseltjuuh]

I'm using an STM32F401RCT6 to create a very accurate millisecond timer for a school project. When the second interrupt of the alarm triggers i set a new CCR1 value and reset the timer. But it seems like the timer just ignores this. Only when i set a breakpoint in the function and resume it updates. Can anyone help me?

Everything else works, i get a square wave of 50%. But it just doesnt seem to update.

[waclawek.jan · Accepted solution]

Timer prescaler TIMx_PSC is unconditionally preloaded, it means, that the new value does not get into effect until the next Update (overflow) of the timer.

TIMx_CCRx may be preloaded, too; see TIMx_CCMRx.OCxPE.

JW