diff --git a/lib/vfd.c b/lib/vfd.c
index d1816c5..8a7a8ec 100644
--- a/lib/vfd.c
+++ b/lib/vfd.c
@@ -477,6 +477,18 @@ void vfd_off(void)
 	gpio_set(VFD_PORT, VFD_STR); // disable HV output
 }
 
+/* output data on the parts */
+void vfd_refresh_on(void)
+{
+	timer_enable_counter(VFD_TIMER); // start timer to periodically output that to the parts
+}
+
+/* stop outputting data on the parts*/
+void vfd_refresh_off(void)
+{
+	timer_disable_counter(VFD_TIMER); // stop timer to periodically output that to the parts
+}
+
 /* setup VFD */
 void vfd_setup(void)
 {
@@ -522,11 +534,9 @@ void vfd_setup(void)
 	timer_reset(VFD_TIMER); // reset timer state
 	timer_set_mode(VFD_TIMER, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock,edge alignment (simple count), and count up
 	timer_set_prescaler(VFD_TIMER, (SYSTEM_CLOCK_FREQ/(1<<16))-1); // set the prescaler so this 16 bits timer overflows at 1Hz
-	//timer_set_period(0xffff/(VFD_DIGITS+VFD_MATRIX)/150); // set the refresh frequency
-	timer_set_period(VFD_TIMER, 0xfffff);
+	timer_set_period(VFD_TIMER, 0xffff/(VFD_DIGITS+VFD_MATRIX)/150); // set the refresh frequency
 	timer_enable_irq(VFD_TIMER, TIM_DIER_UIE); // enable interrupt for timer
 	nvic_enable_irq(VFD_TIMER_IRQ); // allow interrupt for timer
-	timer_enable_counter(VFD_TIMER); // enable timer
 	
 	vfd_clear(); // initialize values
 }
@@ -557,9 +567,21 @@ void tim4_isr(void)
 void tim5_isr(void)
 #endif
 {
+	static uint8_t vfd_mux = 0; // which part to output
+
 	if (timer_get_flag(VFD_TIMER, TIM_SR_UIF)) { // overflow even happened
 		timer_clear_flag(VFD_TIMER, TIM_SR_UIF); // clear flag
-		gpio_toggle(LED_PORT, LED_PIN); // toggle LED
+		if (vfd_mux<LENGTH(vfd_digits)) {
+			if (vfd_digits[vfd_mux]!=0) { // skip unused digits
+				vfd_digit(vfd_mux,vfd_digits[vfd_mux]); // set digit
+				vfd_shift(); // shift out data
+			}
+		} else if (vfd_mux<LENGTH(vfd_digits)+LENGTH(vfd_matrixs)) {
+			if (vfd_matrixs[vfd_mux-LENGTH(vfd_digits)]!=0) { // skip unused matrix
+				vfd_matrix(vfd_mux-LENGTH(vfd_digits),vfd_matrixs[vfd_mux-LENGTH(vfd_digits)]); // set matrix
+				vfd_shift(); // shift out data
+			}
+		}
+		vfd_mux = (vfd_mux+1)%(LENGTH(vfd_digits)+LENGTH(vfd_matrixs)); // got to next segment
 	}
-	//gpio_toggle(LED_PORT, LED_PIN); // toggle LED
 }
diff --git a/lib/vfd.h b/lib/vfd.h
index a39c889..eb438cf 100644
--- a/lib/vfd.h
+++ b/lib/vfd.h
@@ -45,5 +45,9 @@ void vfd_transmit(void);
 void vfd_on(void);
 /* switch VFD display off */
 void vfd_off(void);
+/* output data on the parts */
+void vfd_refresh_on(void);
+/* stop outputing data on the parts*/
+void vfd_refresh_off(void);
 /* setup VFD */
 void vfd_setup(void);
diff --git a/main.c b/main.c
index 8e7b13e..329522b 100644
--- a/main.c
+++ b/main.c
@@ -93,6 +93,7 @@ int main(void)
 	vfd_shift();
 	
 	bool vfd_flag = false;
+	bool refresh = true;
 	for (uint8_t i=0; i<LENGTH(vfd_digits); i++) {
 		vfd_digits[i] = '0'+i;
 	}
@@ -111,7 +112,8 @@ int main(void)
 		while (vfd_flag) {
 			vfd_flag = false;
 			gpio_toggle(LED_PORT, LED_PIN); // toggle LED
-			vfd_transmit();
+			refresh ? vfd_refresh_on() : vfd_refresh_off();
+			refresh = !refresh;
 		}
 		__WFI(); // go to sleep
 	}