protab/timer5-pwm/timer.c

   1 #include <libopencm3/cm3/nvic.h>
   2 #include <libopencm3/stm32/rcc.h>
   3 #include <libopencm3/stm32/gpio.h>
   4 #include <libopencm3/stm32/timer.h>
   5
   6 int up = 1;
   7 int pwm;
   8
   9 void tim4_isr(void)
  10 {
  11         if (TIM_SR(TIM4) & TIM_SR_UIF) {
  12                 TIM_SR(TIM4) &= ~TIM_SR_UIF;
  13                 if (up) {
  14                         pwm += 5;
  15                         if (pwm == 1000) {
  16                                 pwm = 995;
  17                                 up = 0;
  18                         }
  19                 } else {
  20                         pwm -= 5;
  21                         if (pwm < 0) {
  22                                 pwm = 5;
  23                                 up = 1;
  24                         }
  25                 }
  26                 timer_set_oc_value(TIM3, TIM_OC3, pwm);
  27         }
  28 }
  29
  30 int main(void)
  31 {
  32         rcc_clock_setup_in_hse_8mhz_out_72mhz();
  33         rcc_periph_clock_enable(RCC_GPIOB);
  34         rcc_periph_clock_enable(RCC_GPIOC);
  35         rcc_periph_clock_enable(RCC_TIM3);
  36         rcc_periph_clock_enable(RCC_TIM4);
  37         rcc_periph_reset_pulse(RST_TIM3);       // XXX
  38         rcc_periph_reset_pulse(RST_TIM4);       // XXX
  39
  40         // PC13 = BluePill LED
  41         gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
  42         gpio_set(GPIOC, GPIO13);
  43
  44         // PB0 = TIM3_CH3
  45         gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO0);
  46
  47         timer_set_prescaler(TIM3, 1);           // 72 MHz / 2 = 36 MHz
  48         timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
  49         timer_set_period(TIM3, 999);            // 36 MHz / 1000 = 36 kHz
  50         timer_update_on_overflow(TIM3);
  51
  52         timer_set_oc_mode(TIM3, TIM_OC3, TIM_OCM_PWM1);
  53         timer_set_oc_value(TIM3, TIM_OC3, 50);
  54         timer_set_oc_polarity_high(TIM3, TIM_OC3);
  55         timer_enable_oc_output(TIM3, TIM_OC3);
  56
  57         timer_enable_counter(TIM3);
  58
  59         timer_set_prescaler(TIM4, 35999);       // 72 MHz / 36000 = 2 kHz
  60         timer_set_mode(TIM4, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
  61         timer_set_period(TIM4, 2);              // 2 kHz / 2 = 1 kHz
  62         timer_update_on_overflow(TIM4);
  63         timer_enable_irq(TIM4, TIM_DIER_UIE);
  64         nvic_enable_irq(NVIC_TIM4_IRQ);
  65         timer_enable_counter(TIM4);
  66
  67         for (;;) {
  68                 asm volatile ("wfi");
  69         }
  70
  71         return 0;
  72 }