Use USART2

src/main.c

@@ -6,6 +6,7 @@
 #include "flash.h"
 #include "pwr.h"
 #include "timer.h"
+#include "usart.h"
 
 #define exit 42
 
@@ -75,8 +76,10 @@ static void system_clock_init(void) {
 int main(void) {
   (void) system_clock_init();
   (void) tim4_init();
+  (void) usart2_init();
 
   (void) tim4_start();
+  (void) usart2_start();
 
   uint16_t led = PIN('C', 13);           // Blue LED
   RCC->AHB1ENR |= (1 << PINPORT(led));   // Enable GPIO clock for LED
@@ -89,6 +92,8 @@ int main(void) {
 	 led_on = !led_on;
 	 gpio_write(led, led_on);
 
+	 usart2_write("hello, world!\n");
+
 	 counter = TIM4->CNT;
 	}
   };