diff --git a/main.c b/main.c
index 1e957a2..dc80370 100644
--- a/main.c
+++ b/main.c
@@ -52,39 +52,60 @@ int _write(int file, char *ptr, int len)
 	return -1;
 }
 
-static void clock_setup(void)
+/* switch on LED */
+void led_on(void)
 {
-	rcc_clock_setup_in_hse_8mhz_out_72mhz(); // use 8 MHz high speed external clock to generate 72 MHz internal clock
-	rcc_periph_clock_enable(LED_RCC); //enable clock for LED
+#ifdef SYSTEM_BOARD
+	gpio_clear(LED_PORT, LED_PIN);
+#elif MAPLE_MINI
+	gpio_set(LED_PORT, LED_PIN);
+#endif
 }
 
-static void gpio_setup(void)
+/* switch off LED */
+void led_off(void)
 {
-	gpio_set_mode(LED_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, LED_PIN); // set LED pin to 'output push-pull'	
+#ifdef SYSTEM_BOARD
+	gpio_set(LED_PORT, LED_PIN);
+#elif MAPLE_MINI
+	gpio_clear(LED_PORT, LED_PIN);
+#endif
+}
+
+/* toggle LED */
+void led_toggle(void)
+{
+	gpio_toggle(LED_PORT, LED_PIN);
 }
 
 int main(void)
 {	
 	SCB_VTOR = (uint32_t) 0x08002000; // relocate vector table because of the bootloader
 
-	clock_setup(); // setup main clock
-	gpio_setup(); // setup main inputs/ouputs
+	rcc_clock_setup_in_hse_8mhz_out_72mhz(); // use 8 MHz high speed external clock to generate 72 MHz internal clock
+
+	// setup LED
+	rcc_periph_clock_enable(LED_RCC); //enable clock for LED
+	gpio_set_mode(LED_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, LED_PIN); // set LED pin to 'output push-pull'
+	led_off(); // switch off LED to indicate setup started
+
 	usart_setup(); // setup USART (for printing)
 	cdcacm_setup(); // setup USB CDC ACM (for printing)
 	
 	setbuf(stdout, NULL); // set standard out buffer to NULL to immediately print	
 	setbuf(stderr, NULL); // set standard error buffer to NULL to immediately print
 
-	printf("welcome to the STM32F1 CuVoodoo example code\n");
+	printf("welcome to the STM32F1 CuVoodoo example code\n"); // print welcome message
+	led_on(); // switch on LED to indicate setup completed
 
-	/* blink the LED with every transmitted character */
-	while (1) {
+	/* toggle the LED with every transmitted character */
+	while (true) { // infinite loop
 		while (usart_received) { // echo every received character
-			gpio_toggle(LED_PORT, LED_PIN); // toggle LED
+			led_toggle(); // toggle LED
 			printf("%c",usart_getchar()); // transmit receive character
 		}
 		while (cdcacm_received) { // echo every received character
-			gpio_toggle(LED_PORT, LED_PIN); // toggle LED
+			led_toggle(); // toggle LED
 			printf("%c",cdcacm_getchar()); // transmit receive character
 		}
 		__WFI(); // go to sleep