diff --git a/src/main.c b/src/main.c
index f07196d..b43973d 100755
--- a/src/main.c
+++ b/src/main.c
@@ -1,4 +1,34 @@
+#include <string.h>
+
 #include "stm32f0xx_conf.h"
+#include "stm32f0xx_rtc.h"
+#include "stm32f0xx_usart.h"
+
+static int puts(const char *str)
+{
+	const char *p = str;
+	char c;
+
+	for (c = *p++; c; c = *p++) {
+		while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) != SET) ;
+		USART_SendData(USART1, c);
+	}
+}
+
+static char bcd2char(uint8_t bcd)
+{
+	if (bcd < 0xA)
+		return '0' + bcd;
+	else
+		return 'A' + (bcd - 0xA);
+}
+
+static void bcd2str(char *out, uint8_t bcd)
+{
+	*out++ = bcd2char(bcd >> 4);
+	*out++ = bcd2char(bcd & 0xF);
+}
+
 
 void SysTick_Handler(void) {
   static uint16_t tick = 0;
@@ -8,9 +38,52 @@ void SysTick_Handler(void) {
   		tick = 0;
   		GPIOC->ODR ^= (1 << 8);
   		break;
+	case 25:
+		USART_SendData(USART1, 'A');
+		break;
+	case 75:
+		USART_SendData(USART1, 'z');
+		break;
+	case 50:
+		{
+			RTC_TimeTypeDef time;
+			char buf[128];
+
+			RTC_GetTime(RTC_Format_BCD, &time);
+			memset(buf, 0, sizeof(buf));
+			//sprintf(buf, "%02x:%02x:%02x\r\n", time.RTC_Hours, time.RTC_Minutes, time.RTC_Seconds);
+			bcd2str(buf, time.RTC_Seconds);
+			strcpy(buf+2, "s\r\n");
+
+			puts(buf);
+		}
+		break;
   }
 }
 
+static GPIO_InitTypeDef gpioa9 = {
+	.GPIO_Pin	= GPIO_Pin_9 | GPIO_Pin_10,
+	.GPIO_Mode	= GPIO_Mode_AF,
+	.GPIO_Speed	= GPIO_Speed_Level_1,
+	.GPIO_OType	= GPIO_OType_PP,
+	.GPIO_PuPd	= GPIO_PuPd_UP,
+};
+
+static RTC_InitTypeDef rtcinit = {
+	.RTC_HourFormat = RTC_HourFormat_24,
+	.RTC_AsynchPrediv = (128-1),
+	.RTC_SynchPrediv = (256-1),
+};
+
+static USART_InitTypeDef usartinit = {
+	.USART_BaudRate = 115200,
+	.USART_WordLength = USART_WordLength_8b,
+	.USART_StopBits = USART_StopBits_1,
+	.USART_Parity = USART_Parity_No,
+	.USART_Mode = USART_Mode_Rx | USART_Mode_Tx,
+	.USART_HardwareFlowControl = USART_HardwareFlowControl_None,
+};
+
 int main(void)
 {
 
@@ -19,8 +92,39 @@ int main(void)
 
 	GPIOC->MODER = (1 << 16);
 
+	/* UART */
+	//RCC_USARTCLKConfig(RCC_USART1CLK_SYSCLK);
+	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
+	RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
+	GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_1);
+	GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_1);
+	GPIO_Init(GPIOA, &gpioa9);
+	USART_Init(USART1, &usartinit);
+	USART_Cmd(USART1, ENABLE);
+
+#if 1
+	RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);
+	PWR_BackupAccessCmd(ENABLE);
+
+	/* Low-Speed External Oscillator */
+	RCC_LSEConfig(RCC_LSE_ON);
+	RCC_LSEDriveConfig(RCC_LSEDrive_High);
+	/* wait for LSERDY */
+	while (!(RCC_GetFlagStatus(RCC_FLAG_LSERDY)));
+#else
+	RCC_LSICmd(ENABLE);
+	while (!(RCC_GetFlagStatus(RCC_FLAG_LSIRDY)));
+#endif
+
+	/* RTC */
+	RCC_RTCCLKConfig(RCC_RTCCLKSource_LSE);
+	RCC_RTCCLKCmd(ENABLE);
+	RTC_Init(&rtcinit);
+
 	SysTick_Config(SystemCoreClock/100);
 
+	puts("\r\nEntering main...\r\n");
+
 	while(1);
 
 }