What's wrong in PWM (Led)?

[wsevendays]

Posted on December 03, 2011 at 10:50

I want to create fading Led with pwm, but my code doesn't works. If I simply set bit 1 to pin my led is lights.Please help me.

I'm use stm32f103vet6.

int main(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

 TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;

 TIM_OCInitTypeDef TIM_OCInitStruct;

   RCC_APB2PeriphClockCmd(

           RCC_APB2Periph_GPIOB |

           RCC_APB2Periph_AFIO, ENABLE );

   RCC_APB1PeriphClockCmd( RCC_APB1Periph_TIM3, ENABLE );

   // Set the Vector Table base address at 0x08000000.

   NVIC_SetVectorTable( NVIC_VectTab_FLASH, 0x0 );

   NVIC_PriorityGroupConfig( NVIC_PriorityGroup_4 );

   // Configure HCLK clock as SysTick clock source.

   SysTick_CLKSourceConfig( SysTick_CLKSource_HCLK );

   GPIO_StructInit(&GPIO_InitStructure); // Reset init structure

   // Setup Blue LED on STM32-Discovery Board to use PWM.

   GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_10;

   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;            // Alt Function - Push Pull

   GPIO_Init( GPIOB, &GPIO_InitStructure );

   GPIO_PinRemapConfig( GPIO_FullRemap_TIM3, ENABLE );        // Map TIM3_CH3 to GPIOC.Pin8

   // Let PWM frequency equal 100Hz.

   // Let period equal 1000. Therefore, timer runs from zero to 1000. Gives 0.1Hz resolution.

   // Solving for prescaler gives 240.

   TIM_TimeBaseStructInit( &TIM_TimeBaseInitStruct );

   TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV4;

   TIM_TimeBaseInitStruct.TIM_Period = 1000 - 1;   // 0..999

   TIM_TimeBaseInitStruct.TIM_Prescaler = 240 - 1; // Div 240

   TIM_TimeBaseInit( TIM3, &TIM_TimeBaseInitStruct );

   TIM_OCStructInit( &TIM_OCInitStruct );

   TIM_OCInitStruct.TIM_OutputState = TIM_OutputState_Enable;

   TIM_OCInitStruct.TIM_OCMode = TIM_OCMode_PWM1;

   // Initial duty cycle equals 0%. Value can range from zero to 1000.

   TIM_OCInitStruct.TIM_Pulse = 999; // 0 .. 1000 (0=Always Off, 1000=Always On)

   TIM_OC3Init( TIM3, &TIM_OCInitStruct );

   TIM_UpdateDisableConfig(TIM3,ENABLE);

   TIM_Cmd( TIM3, ENABLE );

while (1);

}

#pwm #led #stm32 #stm32f103

[Tesla DeLorean]

Posted on December 03, 2011 at 22:35

Not GPIOB ! If you want to use PC.8 = TIM3_CH3 (remapped), initialize the GPIOC clock, and GPIOC pin. If you really want in on GPIOB you must not remap it, and it will come out PB.0

pulse width = 999, is pretty much totally ON (a multimeter will read 3.xV). If you want it to pulse 500 might be a better initial value. And probably needs to be much lower to appear DIM.

If you want it to phase DIM/BRIGHT you will need to shovel different cyclic PWM values via DMA or at the update interrupt. 

[wsevendays]

Posted on December 04, 2011 at 09:49

Thanks. I was wrong.I now

get

to control

how

bright

is

the light.Can you please show how to update value of brightness?

[rmteo]

Posted on December 04, 2011 at 18:39

You can use the library function but I find it just as easy to use:

TIM_SetCompare3(TIM3, 200);

[wsevendays]

Posted on December 04, 2011 at 19:00

Thank you so much

!

You

have helped me

incredibly

.

[rmteo]

Posted on December 04, 2011 at 19:40

You're welcome.  Actually, what I meant to say is this (which will save you about 12 bytes of code space over the previous way), but either method will work.

TIM3->CCR3 = 200;

[wsevendays]

Posted on December 04, 2011 at 22:02

Thanks. A also viewed this on

https://my.st.com/public/STe2ecommunities/mcu/Lists/STM32VLDiscovery/DispForm.aspx?ID=422&RootFolder=/public/STe2ecommunities/mcu/Lists/STM32VLDiscovery/Example PWM on STM32-Discovery Blue LED&Source=https://my.st.com/public/STe2ecommunities/mcu/Lists/STM32VLDiscovery/flat.aspx?RootFolder%3D%252Fpublic%252FSTe2ecommunities%252Fmcu%252FLists%252FSTM32VLDiscovery%252FExample%2520PWM%2520on%2520STM32-Discovery%2520Blue%2520LED%26FolderCTID%3D0x01200200770978C69A1141439FE559EB459D758000491D59B8574F8049B5DFA3E8B21CBA51%26currentviews%3D591

But my delay was very little so I don't saw changes, now I'm set it to (80000-200000) and all goes perfect.