diff --git a/lib/vfd.c b/lib/vfd.c
index ce5db23..3aaf22b 100644
--- a/lib/vfd.c
+++ b/lib/vfd.c
@@ -347,7 +347,6 @@ void vfd_shift(void)
 	gpio_clear(VFD_PORT, VFD_NLE); // do not latch data
 	gpio_set(VFD_PORT, VFD_CLK); // clock is idle high	
 	for (uint8_t i=0; i<sizeof(vfd_data)/sizeof(vfd_data[0]); i++) {
-		//printf("%08lx ",vfd_data[i]);
 		for (uint8_t b=0; b<32; b++) {
 			gpio_clear(VFD_PORT, VFD_CLK); // change data on low
 			if (vfd_data[i]&(1<<b)) { // shift the value
@@ -358,11 +357,16 @@ void vfd_shift(void)
 			gpio_set(VFD_PORT, VFD_CLK); // signal need to be valid on high edge
 		}
 	}
-	//printf("\n");
+	
 	gpio_set(VFD_PORT, VFD_STR); // disable HV output
 	gpio_set(VFD_PORT, VFD_NLE); // latch data
 	gpio_clear(VFD_PORT, VFD_STR); // enable HV output
 	gpio_clear(VFD_PORT, VFD_NLE); // stop latching data
+	
+	// let the fluorescence glow up a bit
+	for (uint32_t i = 0; i < 0x2000; i++) {
+		__asm__("nop");
+	}
 }
 
 /* transmit each digit and dot */
@@ -374,6 +378,24 @@ static void vfd_transmit(void)
 }
 */
 
+/* clear VFD display
+ * the data has to be transmitted separately */
+void vfd_clear(void)
+{
+	for (uint8_t i=0; i<LENGTH(vfd_data); i++) {
+		vfd_data[i] = 0;
+	}
+}
+
+/* test VFD display (light up all anodes)
+ * the data has to be transmitted separately */
+void vfd_test(void)
+{
+	for (uint8_t i=0; i<LENGTH(vfd_data); i++) {
+		vfd_data[i] = ~0;
+	}
+}
+
 /* setup VFD */
 void vfd_setup(void)
 {
@@ -382,4 +404,8 @@ void vfd_setup(void)
 	gpio_set_mode(VFD_PORT, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, VFD_NLE); // set VFD pin to 'output push-pull'
 	gpio_set_mode(VFD_PORT, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, VFD_CLK); // set VFD pin to 'output push-pull'
 	gpio_set_mode(VFD_PORT, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, VFD_DIN); // set VFD pin to 'output push-pull'
+	
+	gpio_set(VFD_PORT, VFD_STR); // disable HV output
+	gpio_clear(VFD_PORT, VFD_NLE); // do not latch data
+	gpio_set(VFD_PORT, VFD_CLK); // clock is idle high
 }
diff --git a/lib/vfd.h b/lib/vfd.h
index ac9bcb4..1ac2ac7 100644
--- a/lib/vfd.h
+++ b/lib/vfd.h
@@ -32,5 +32,11 @@ void vfd_digit(uint8_t nb, char c);
 void vfd_matrix(uint8_t nb, char c);
 /* shift out the VFD data */
 void vfd_shift(void);
+/* clear VFD display
+ * the data has to be transmitted separately */
+void vfd_clear(void);
+/* test VFD display (light up all anodes)
+ * the data has to be transmitted separately */
+void vfd_test(void);
 /* setup VFD */
 void vfd_setup(void);
diff --git a/main.c b/main.c
index 14f1a61..0179018 100644
--- a/main.c
+++ b/main.c
@@ -73,22 +73,24 @@ int main(void)
 	setbuf(stderr, NULL); // set standard error buffer to NULL to immediately print
 
 	printf("welcome to the STM32F1 CuVoodoo display driver\n");
-	
-	gpio_set(VFD_PORT, VFD_STR); // disable HV output
-	gpio_clear(VFD_PORT, VFD_NLE); // do not latch data
-	gpio_set(VFD_PORT, VFD_CLK); // clock is idle high
 
 	bool vfd_transmit = false;
 	uint8_t digit = 0;
 	uint8_t matrix = 0;
 	char c = 0x80;
-	
-	vfd_digit(digit,'0');
+
+	vfd_clear();
 	vfd_shift();
-	// let the fluorescence glow up a bit
-	for (uint32_t i = 0; i < 0x2000; i++) {
+	for (uint32_t i = 0; i < 0x800000; i++) {
 		__asm__("nop");
 	}
+	vfd_test();
+	vfd_shift();
+	for (uint32_t i = 0; i < 0x800000; i++) {
+		__asm__("nop");
+	}
+	vfd_digit(digit,'0');
+	vfd_shift();
 	
 	while (true) {
 		while (usart_received) { // echo every received character
@@ -107,12 +109,8 @@ int main(void)
 			
 			vfd_matrix(matrix,c);
 			vfd_shift();
-			// let the fluorescence glow up a bit
-			for (uint32_t i = 0; i < 0x2000; i++) {
-				__asm__("nop");
-			}
-			matrix = (matrix+1)%12;
-			
+
+			matrix = (matrix+1)%12;			
 			c++;
 		}
 		__WFI(); // go to sleep