diff --git a/src/rtc.c b/src/rtc.c
--- a/src/rtc.c
+++ b/src/rtc.c
@@ -7,7 +7,15 @@
 #include "gpio.h"
 
 
-RTC_HandleTypeDef hrtc;
+static RTC_HandleTypeDef hrtc;
+static volatile uint32_t seconds_ctr = 0;
+
+
+void rtc_incseconds(void)
+{
+	//HAL_GPIO_TogglePin(LED_BLUE);
+	seconds_ctr += 1;
+}
 
 static void Error_Handler(void)
 {
@@ -94,14 +102,16 @@ void rtc_init(void)
 
 }
 
-RTC_TimeTypeDef time_last = {0};
+static RTC_TimeTypeDef time_last = {0};
 
+// Get the time from the RTC
 RTC_TimeTypeDef* rtc_time(void)
 {
 	HAL_RTC_GetTime(&hrtc, &time_last, RTC_FORMAT_BCD);
 	return &time_last;
 }
 
+// Calculate value in milliseconds from subseconds of the RTC
 uint16_t __rtc_millis(uint32_t sub_seconds)
 {
 	// Subsecond counter counts down from SynchPrediv value to zero
@@ -110,6 +120,7 @@ uint16_t __rtc_millis(uint32_t sub_secon
 
 #define JULIAN_DATE_BASE 2440588 // Unix epoch time in Julian calendar (UnixTime = 00:00:00 01.01.1970 => JDN = 2440588)
 
+// Calculate timestamp in milliseconds since Unix epoch
 uint64_t rtc_timestamp(void)
 {
 	RTC_TimeTypeDef time = {0};
@@ -154,12 +165,20 @@ uint64_t rtc_timestamp(void)
 
 }
 
+uint32_t rtc_timestamp_seconds(void)
+{
+	return seconds_ctr;
+}
 
+
+// Calibrate the RTC somehow
 void rtc_cal(void)
 {
 	// Do something with hrtc.Instance->CALR; // this has a plus and minus component, see refman
 }
 
+
+// RTC accessor
 RTC_HandleTypeDef* rtc_gethandle(void)
 {
 	return &hrtc;