stm32g071rb problem with PWM generation using TIM1 and PA8 pin

[dmrsim]

Hello,

I'm studing timers with stm32g071rb and I wanna generate a PWM signal using PA8 pin.
At the moment I write this code:

GPIOA->MODER &= 0xeffcffff;

GPIOA->MODER |= 2<<16; //alternate function mode for PA8

GPIOA->OSPEEDR |= 1<<17; //PA8 at high speed

GPIOA->AFR[1] |= 2; //alternate function for PA8(TIM1_CH1)

rcc->APBENR2 |= RCC_APBENR2_TIM1EN_Msk;

rcc->IOPENR |= RCC_IOPENR_GPIOAEN_Msk;

timer->ARR = 20;

timer->PSC = 16000 - 1;

timer->CCR1 = 1;

timer->CCMR1 |=  0x60; //PWM mode 1

timer->CCMR1 |= TIM_CCMR1_OC1PE_Msk;

timer->CR1 |= TIM_CR1_ARPE_Msk;

timer->EGR = TIM_EGR_UG_Msk;

timer->CCER |= 1 << 0;

timer->CR1 |= TIM_CR1_CEN_Msk;

I connected an oscilloscope in PA8 pin but there is no signal...
Please could you help me?

Thanks a lot!

[dmrsim]

GPIOA->MODER &= 0xeffcffff;
GPIOA->MODER |= 2<<16; //alternate function mode for PA8
GPIOA->OSPEEDR |= 1<<17; //PA8 at high speed
GPIOA->AFR[1] |= 2; //alternate function for PA8(TIM1_CH1)
 
rcc->APBENR2 |= RCC_APBENR2_TIM1EN_Msk;
rcc->IOPENR |= RCC_IOPENR_GPIOAEN_Msk;
timer->ARR = 20;
timer->PSC = 16000 - 1;
timer->CCR1 = 1;
timer->CCMR1 |=  0x60; //PWM mode 1
timer->CCMR1 |= TIM_CCMR1_OC1PE_Msk;
timer->CR1 |= TIM_CR1_ARPE_Msk;
timer->EGR = TIM_EGR_UG_Msk;
timer->CCER |= 1 << 0;
timer->CR1 |= TIM_CR1_CEN_Msk;

I repost the code using tag

[waclawek.jan · Accepted solution]

You need to enable GPIOA clock *before* you write to GPIOA registers.

Also, TIM1 is an Advanced timer and you need to set TIM1_BDTR.MOE to get it output PWM.

What are "rcc" and "timer"?

Always start debugging by reading out and checking the relevant registers content, e.g. in debugger.

JW

[dmrsim]

@waclawek.jan Thanks a lot, you solved me a problem that keep me stuck for 2 days!!
For your information, rcc and timer are:

RCC_TypeDef *rcc = RCC;
TIM_TypeDef *timer = TIM1;

 I missing these lines in the documentation:

 OCx output is enabled by a combination oft the CCxE, CCxNE, MOE, OSSI and OSSR bits (TIMx_CCER and TIMx_BDTR registers)

So after I put this line as you as you said, I solved my problem:

timer->BDTR |= TIM_BDTR_MOE_Msk;

Thanks again @waclawek.jan