PWM formula timer5 not work

[bfran.1]

I'm using STM32l152 and use TIM5_Ch2 for generate pwm .

My target frquency pwm is 2.85 KHz .

I using these parameter:

clock frequency = 32MHz

 htim5.Init.Prescaler = 6; 

 htim5.Init.Period = 100; 

I measured pwm on oscilloscope and I measure 2.85KHz with 50% duty cicle .

The formula that used is :

Frequency_pwm = ClockFreq / ((PSC + 1) * (ARR + 1))

where am i wrong?

BR.

Francesco

[waclawek.jan]

> My target frquency pwm is 2.85 KHz .

> I measured pwm on oscilloscope and I measure 2.85KHz with 50% duty cicle .

What's the problem, exactly?

In any case, read out and check/post the TIM registers content, and post the clocks (AHB/APB) setup (if in doubts, output clock onto MCO and measure, and/or also check/post relevant RCC registers content).

JW

[bfran.1]

this my register ..

Yu can tell me the values of f clock and if

Frequency_pwm = ClockFreq / ((PSC + 1) * (ARR + 1)) = 2.85 KHz ?

Thanks

[waclawek.jan]

RCC_CFGR.SW=0 which means you are running from MSI, RCC_ICSCR.MSIRANGE = 0b101 i.e. MSI runs around 2.097MHz. There's no APB prescaler in RCC_CFGR i.e. APB thus TIM clock is 2.097MHz. TIM is set to period 2097000/(6+1)/(100+1)=2.966kHz. TIM configuration is not finished, it's not running, nor is any channel enabled in CCER, nor is any CCRx set to other than 0, so I don't know what would an output look like exactly.

Note, that MSI is an RC oscillator, i.e. it has some error, see datasheet.

I still don't know, what was the question.

JW