/* p11_2.c Using TIM16 for PWM Output
 *
 * This program configures TIM16 with prescaler divides by 10
 * so that the timer counter is counting at 1.6 MHz.
 * ARR register is loaded with 26666 and CCR1 is loaded with 8888.
 * The channel 1 is configured as PWM mode. The output of Ch1N is
 * turned on when the counter starts counting from 0. When the
 * counter matches the content of CCR1, Ch1N output is turned off.
 * When the counter matches ARR, the counter is cleared to 0 and
 * the output is turned on and the counter starts counting up again.
 * The LED will be on for 8889/26667 = 30% of the time.
 * The output pin of TIM16 Ch1N is PB6 and the alternate function
 * of PB6 should be set to AF2.
 *
 * This program is similar to p11_1.c except:
 * 1. Each PWM output channel (Chx) has a complementary output (ChxN)
 *    and we are using the Ch1N output.
 * 2. The output needs to be enabled at TIM16_BDTR register.
 *
 * This program was tested with Keil uVision v5.23 with DFP v2.0.0.
 */

#include "stm32f0xx.h"

int main(void) {
    RCC->AHBENR |=  0x00040000;     /* enable GPIOB clock */
    GPIOB->AFR[0] |= 0x02000000;    /* PB6 pin for TIM16 channel N1 */
    GPIOB->MODER &= ~0x00003000;
    GPIOB->MODER |=  0x00002000;

    /* setup TIM16 */
    RCC->APB2ENR |= 0x00020000;     /* enable TIM16 clock */
    TIM16->PSC = 5 - 1;             /* divided by 5 */
    TIM16->ARR = 26667 - 1;         /* divided by 26667 */
    TIM16->CNT = 0;
    TIM16->CCMR1 = 0x0060;          /* PWM mode */
    TIM16->CCER = 4;                /* enable PWM ChN1 */
    TIM16->BDTR = 0x8000;           /* enable main output enable */
    TIM16->CCR1 = 8889;             /* pulse width 1/3 of the period */
    TIM16->CR1 = 1;                 /* enable timer */

    while(1) {
    }
}