My Objective is to Generate PWM with duty cycle = 50 % , Frequency = 50 Hz using General Purpose Timer 2 in output channel 2 which is at PA1 or pin number 11 My Target System is STM32 BluePill development board
- Target Controller is STM32F103C8T6 MEDIUM DENSITY DEVICE
- Target board crystal is 8 MHz
- I use Keil Micro vision 4 evaluation version IDE for programming and debugging
- Debugger : ST-LINK V2
I configured the GPIOA in Alternate function output Push Pull mode with maximum frequency not exceeding 50 MHz, I connected an LED bulb to the GPIOA pin 1, but the LED went on glowing without reduction in the brightness level. The LED was still glowing even after i performed a test with duty cycle set to 0. On the debugger window I could see exactly all the parameters I configured and the Count register was getting incremented. I cannot find information regarding selection of alternate functions for a GPIO Port.
my code:
/**************************** Header file *******************************/
#include<stm32f10x.h>
/*************************** user defined function **********************/
/************************************************************************
Name : PWM_Init()
Description : Initializes PWM hardware and associated GPIO ports
Enables clocks for peripherals and configure modes
Parameters : None
Return_val : None
************************************************************************/
void PWM_Init()
{
/****configure clocks for PORTA & TIMER2********/
RCC->APB2ENR |= RCC_APB2ENR_IOPAEN; // enable port a clock
RCC->APB1ENR |= RCC_APB1ENR_TIM2EN; // enable clock for timer 2
/***** configure GPIOA mode *******************/
/* Porta Pin 1 &2 as alternate function output Push pull 50 MHz */
GPIOA->CRL = 0x000000bb;
/*******Set timer 2 Period for PWM**************
Timer Clock = 72MHz = 72000000 Hz
Time Period Required = (1/50Hz) = 0.02 Seconds
Let ARR value be 65535 then,
Prescalar + 1 = 72000000/((ARR+1)*50Hz)
Prescalar = 21 (approx)
***********************************************/
TIM2->ARR = 65535; // Set Auto reload value
TIM2->PSC = 21; // Set Prescalar value
/* Output Compare Mode, ENABLE Preload,PWM mode:2*/
TIM2->CCMR1 = 0x00007800;
TIM2->EGR |= TIM_EGR_UG; // ENABLE update generation
/*CC2E : channel 2 enabled; polarity : active high*/
TIM2->CCER = 0x00000010;
TIM2->CR1 |= TIM_CR1_ARPE; // Auto preload ENABLE
TIM2->CR1 |= TIM_CR1_CEN; // ENABLE Timer counter
}
/**************Main Function**********************************/
int main()
{
PWM_Init(); // initialize PWM
while(1)
{
TIM2->CCR2 = 32768; // SET duty cycle to 50%
}
}
Kindly have a view of my source code and please notify me the corrections that need to be done. The target specifications are mentioned in the source code.
Thank you
