diff --git a/lib/rtc_ds1307.c b/lib/rtc_ds1307.c
index b0ed66d..a4956a9 100644
--- a/lib/rtc_ds1307.c
+++ b/lib/rtc_ds1307.c
@@ -37,6 +37,7 @@
 #include "rtc_ds1307.h" // RTC header and definitions
 
 #if defined(SQUARE_WAVE_TICKS)
+volatile uint32_t rtc_ticks = 0;
 volatile bool rtc_tick_flag = false;
 #endif
 
@@ -450,6 +451,7 @@ void SQUARE_WAVE_TIMER_ISR(void)
 {
     if (timer_get_flag(SQUARE_WAVE_TIMER, TIM_SR_UIF)) { // overflow even happened
         timer_clear_flag(SQUARE_WAVE_TIMER, TIM_SR_UIF); // clear flag
+		rtc_ticks++; // increment count
 		rtc_tick_flag = true; // update flag
     }
 }
diff --git a/lib/rtc_ds1307.h b/lib/rtc_ds1307.h
index 7abe523..2851610 100644
--- a/lib/rtc_ds1307.h
+++ b/lib/rtc_ds1307.h
@@ -52,7 +52,8 @@
 /** @} */
 
 #if defined(SQUARE_WAVE_TICKS)
-extern volatile bool rtc_tick_flag; /**< set on SQUARE_WAVE_TICS square wave tics */
+extern volatile uint32_t rtc_ticks; /**< increment on SQUARE_WAVE_TICS square wave ticks */
+extern volatile bool rtc_tick_flag; /**< set on SQUARE_WAVE_TICS square wave ticks */
 #endif
 
 /** @brief setup communication with RTC IC