/* p5_7.c TIM3 Input Capture
 *
 * This program configures TIM3 CH2 to toggle PC7 as was done in p5_6.
 *
 * The TIM17 CH1 is set to do Input Capture from PA7 (D11). The program
 * waits for capture flag (CC1IF) to set then stores the captured value
 * in a global variable to be watched by the debugger. The flag is
 * cleared by reading CCR1.
 * A jumper should be used to connect PC7 (D9) to PA7 (D11).
 *
 * This program was tested with Keil uVision v5.23 with DFP v2.0.0
 */
#include "stm32f0xx.h"

unsigned short timestamp[8];
int i;

int main(void) {
    // configure PC7 as output of TIM3 CH2
    RCC->AHBENR |=  0x00080000;     /* enable GPIOC clock */
    GPIOC->MODER &= ~0x0000C000;    /* clear pin mode */
    GPIOC->MODER |=  0x00008000;    /* set pin to alternate function */
    GPIOC->AFR[0] &= 0xF0000000;    /* clear pin AF bits to set pin to AF0 for TIM3 CH2 */

    // configure TIM3 to wrap around at 1 Hz
		// and toggle CH2 output when the counter value is 0
    RCC->APB1ENR |= 0x00000002;         /* enable TIM3 clock */
    TIM3->PSC = 800 - 1;                /* divided by 800 */
    TIM3->ARR = 10000 - 1;              /* divided by 10000 */
    TIM3->CCMR1 = 0x3000;               /* set output to toggle on match */
    TIM3->CCR2 = 0;                     /* set match value */
    TIM3->CCER |= 0x10;                 /* enable CH2 compare mode */
    TIM3->CNT = 0;                      /* clear counter */
    TIM3->CR1 = 1;                      /* enable TIM3 */


    // configure PA7 as input of TIM17 CH1
    RCC->AHBENR |=  0X00020000;         /* enable GPIOA clock */
    GPIOA->MODER &= ~0x0000C000;        /* clear pin mode */
    GPIOA->MODER |=  0x00008000;        /* set pin to alternate function */
    GPIOA->AFR[0] &= ~0xF0000000;       /* clear pin AF bits */
    GPIOA->AFR[0] |=  0x50000000;       /* set pin to AF5 for TIM17 CH1 */

    // configure TIM17 to do input capture with prescaler ...
    RCC->APB2ENR |= 0x00040000;         /* enable TIM17 clock */
    TIM17->PSC = 8000 - 1;              /* divided by 8000 */
    TIM17->CCMR1 = 0x41;                /* set CH1 to input */
    TIM17->CCER = 1;                    /* enable CH 1 capture on the rising edge */
    TIM17->CR1 = 1;                     /* enable TIM3 */

    while (1) {
        for (i = 0; i < 8; i++)
        {
            while (!(TIM17->SR & 2)) {}     /* wait until input edge is captured */
            timestamp[i] = TIM17->CCR1;    /* read captured counter value */
        }
        __NOP();	/* for setting breakpoint after 8 iterations */
    }
}