Posted on July 04, 2014 at 17:29
Hi all,
I'm trying to use a PWM on a Olimex STM32-H407 board to drive the green LED (only user LED on the board), but without any success. I managed to use timers for generating output signal to turn on/off the LED, but inside the infinite loop in main program. Now I want to generate this output signal in ''background'', i.e. as a PWM. Here is an example of a code that I've used:
int
main(
void
)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
/* Enable GPIOC */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
/* Enable TIM4 */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);
/* Configure GPIOC to access LED */
GPIO_StructInit(&GPIO_InitStructure);
// initalization
GPIO_PinAFConfig(GPIOC, GPIO_PinSource13, GPIO_AF_TIM4);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
// LED @ Olimex-STM32-H407
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);
TIM_TimeBaseStructInit(&TIM_TimeBaseInitStructure);
// initialization
TIM_TimeBaseInitStructure.TIM_Prescaler = 40000;
// 40 MHz -> 1 kHz (1 ms)
TIM_TimeBaseInitStructure.TIM_Period = 1000;
// 1000 ms = 1 s
TIM_TimeBaseInitStructure.TIM_ClockDivision = 0;
TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseInitStructure);
TIM_OCStructInit(&TIM_OCInitStructure);
// initialization
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_Pulse = 500;
TIM_OC1Init(TIM4, &TIM_OCInitStructure);
/* Enable TIM4 */
TIM_Cmd(TIM4, ENABLE);
while
(1);
}
As a result of this program, LED is always on (this is by default, since LED is on for reset state), but it should be blinking with 50% duty-cycle, and with 1 sec time period.
I also tried to ''send'' a PWM signal on GPIO output and to monitor that port/pin with oscilloscope - in this case the output pin used is always at low level, i.e. in reset state.
Can you please tell me what am I doing wrong?
Thanks!
Best,
Marko.
