Cara mengakses PWM pada STM32F4 Discovery

 Ini ada referensi tentang cara menyalakan PWM menggunakan STM32F4 discovery..

kalau di coba sepertinya hasilnya cukup bagus.Selamat mencoba. Hasilnya seperti ini (+-)

*    PWM example for STM32F4 Discovery

*    It should works on STM32F429 Discovery too and all other STM32F4xx devices

*

*    @author     Tilen Majerle

*    @email        tilen@majerle.eu

*    @website    http://stm32f4-discovery.com

*    @ide        Keil uVision 5

*/

#include "defines.h"

#include "stm32f4xx.h"

#include "stm32f4xx_rcc.h"

#include "stm32f4xx_gpio.h"

#include "stm32f4xx_tim.h"

void TM_LEDS_Init(void) {

    GPIO_InitTypeDef GPIO_InitStruct;

    

    /* Clock for GPIOD */

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

    /* Alternating functions for pins */

    GPIO_PinAFConfig(GPIOD, GPIO_PinSource12, GPIO_AF_TIM4);

    GPIO_PinAFConfig(GPIOD, GPIO_PinSource13, GPIO_AF_TIM4);

    GPIO_PinAFConfig(GPIOD, GPIO_PinSource14, GPIO_AF_TIM4);

    GPIO_PinAFConfig(GPIOD, GPIO_PinSource15, GPIO_AF_TIM4);

    

    /* Set pins */

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;

    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;

    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;

    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_100MHz;

    GPIO_Init(GPIOD, &GPIO_InitStruct);

}

void TM_TIMER_Init(void) {

    TIM_TimeBaseInitTypeDef TIM_BaseStruct;

    

    /* Enable clock for TIM4 */

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

/*    

    TIM4 is connected to APB1 bus, which has on F407 device 42MHz clock                 

    But, timer has internal PLL, which double this frequency for timer, up to 84MHz     

    Remember: Not each timer is connected to APB1, there are also timers connected     

    on APB2, which works at 84MHz by default, and internal PLL increase                 

    this to up to 168MHz                                                             

    

    Set timer prescaller

    Timer count frequency is set with

    

    timer_tick_frequency = Timer_default_frequency / (prescaller_set + 1)        

    

    In our case, we want a max frequency for timer, so we set prescaller to 0         

    And our timer will have tick frequency        

    

    timer_tick_frequency = 84000000 / (0 + 1) = 84000000

*/    

    TIM_BaseStruct.TIM_Prescaler = 0;

    /* Count up */

    TIM_BaseStruct.TIM_CounterMode = TIM_CounterMode_Up;

/*

    Set timer period when it have reset

    First you have to know max value for timer

    In our case it is 16bit = 65535

    To get your frequency for PWM, queasion is simple

    

    PWM_frequency = timer_tick_frequency / (TIM_Period + 1)

    

    If you know your PWM frequency you want to have timer period set correct

    

    TIM_Period = timer_tick_frequency / PWM_frequency - 1

    

    In our case, for 10Khz PWM_frequency, set Period to

    

    TIM_Period = 84000000 / 10000 - 1 = 8399

    

    If you get TIM_Period larger than max timer value (in our case 65535),

    you have to choose larger prescaller and slow down timer tick frequency

*/

    TIM_BaseStruct.TIM_Period = 8399; /* 10kHz PWM */

    TIM_BaseStruct.TIM_ClockDivision = TIM_CKD_DIV1;

    TIM_BaseStruct.TIM_RepetitionCounter = 0;

    /* Initialize TIM4 */

    TIM_TimeBaseInit(TIM4, &TIM_BaseStruct);

    /* Start count on TIM4 */

    TIM_Cmd(TIM4, ENABLE);

}

void TM_PWM_Init(void) {

    TIM_OCInitTypeDef TIM_OCStruct;

    

    /* Common settings */

    

    /* PWM mode 2 = Clear on compare match */

    /* PWM mode 1 = Set on compare match */

    TIM_OCStruct.TIM_OCMode = TIM_OCMode_PWM2;

    TIM_OCStruct.TIM_OutputState = TIM_OutputState_Enable;

    TIM_OCStruct.TIM_OCPolarity = TIM_OCPolarity_Low;

    

/*

    To get proper duty cycle, you have simple equation

    

    pulse_length = ((TIM_Period + 1) * DutyCycle) / 100 - 1

    

    where DutyCycle is in percent, between 0 and 100%

    

    25% duty cycle:     pulse_length = ((8399 + 1) * 25) / 100 - 1 = 2099

    50% duty cycle:     pulse_length = ((8399 + 1) * 50) / 100 - 1 = 4199

    75% duty cycle:     pulse_length = ((8399 + 1) * 75) / 100 - 1 = 6299

    100% duty cycle:    pulse_length = ((8399 + 1) * 100) / 100 - 1 = 8399

    

    Remember: if pulse_length is larger than TIM_Period, you will have output HIGH all the time

*/

    TIM_OCStruct.TIM_Pulse = 2099; /* 25% duty cycle */

    TIM_OC1Init(TIM4, &TIM_OCStruct);

    TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);

    

    TIM_OCStruct.TIM_Pulse = 4199; /* 50% duty cycle */

    TIM_OC2Init(TIM4, &TIM_OCStruct);

    TIM_OC2PreloadConfig(TIM4, TIM_OCPreload_Enable);

    

    TIM_OCStruct.TIM_Pulse = 6299; /* 75% duty cycle */

    TIM_OC3Init(TIM4, &TIM_OCStruct);

    TIM_OC3PreloadConfig(TIM4, TIM_OCPreload_Enable);

    

    TIM_OCStruct.TIM_Pulse = 8399; /* 100% duty cycle */

    TIM_OC4Init(TIM4, &TIM_OCStruct);

    TIM_OC4PreloadConfig(TIM4, TIM_OCPreload_Enable);

}

int main(void) {

    /* Initialize system */

    SystemInit();

    /* Init leds */

    TM_LEDS_Init();

    /* Init timer */

    TM_TIMER_Init();

    /* Init PWM */

    TM_PWM_Init();

    

    while (1) {

    }

}