Blink using interrupts, not delay

main.c

@@ -13,6 +13,7 @@
 #include <libopencm3/stm32/gpio.h>
 #include <libopencm3/stm32/f1/exti.h>
 #include <libopencm3/stm32/f1/nvic.h>
+#include <libopencm3/stm32/f1/timer.h>
 #include <stdbool.h>
 
 //#define DELAY 8000000		// Should be a second, or maybe not (second iff 8MHz clk, 1/3second if 24MHz clk)			// Too long!!
@@ -61,10 +62,30 @@ void setup_exti0_in (void) {
 	exti_enable_request(EXTI0);
 }
 
+void setup_tim6_periodic_irq (void) {
+	// Enable clock
+	rcc_periph_clock_enable(RCC_TIM6);
+	
+	// Config:
+	// Set prescaler
+	timer_set_prescaler(TIM6, 65535);
+	// Set counter value
+	timer_set_period(TIM6, 183);
+
+	// Enable interrupts in NVIC
+	nvic_enable_irq(NVIC_TIM6_IRQ);
+	// Enable sending interrupts from the timer
+	timer_enable_irq(TIM6, TIM_DIER_UIE);
+
+	// Finally, enable the counter
+	timer_enable_counter(TIM6);
+}
+
 void setup (void) {
 	setup_system();
 	setup_gpio_out();
 	setup_exti0_in();
+	setup_tim6_periodic_irq();
 }
 
 // libopencm3 has a pre-declared interrupt handlers, so it needs to have this name
@@ -82,12 +103,23 @@ void exti0_isr (void) {
 	running = true;
 }
 
+void tim6_isr (void) {
+	timer_clear_flag(TIM6, TIM_SR_UIF);
+	// Just change value of GPIO C9 (green LED)
+	uint16_t cur = gpio_get(GPIOC, GPIO9);
+	if (cur) {
+		gpio_clear(GPIOC, GPIO9);
+	} else {
+		gpio_set(GPIOC, GPIO9);
+	}
+}
+
 
 int main (void) {
 	setup();
 
 	// Array of what leds should be on
-	uint16_t states[4] = {0, GPIO9, GPIO8, GPIO9 | GPIO8};
+	uint16_t states[4] = {0, 0, GPIO8, GPIO8};
 	char state = 0;
 	int i;
 
@@ -102,7 +134,7 @@ int main (void) {
 		state = (direction == FORWARD ? (state + 1)%4 : (/*state+4-1*/ state+3)%4 ); // New state
 
 		gpio_set(GPIOC, states[state]);
-		gpio_clear(GPIOC, (GPIO8 | GPIO9) ^ states[state]);
+		gpio_clear(GPIOC, (GPIO8) ^ states[state]);
 	}
 	return 0;
 }