diff --git a/application.c b/application.c
index f8d006d..3c19a08 100644
--- a/application.c
+++ b/application.c
@@ -67,7 +67,6 @@ const uint8_t channels[] = {ADC_CHANNEL17, ADC_CHANNEL(TARGET_CHANNEL), ADC_CHAN
 
 #define CHANNEL_NUMBERS 12 /**< number of target signals */
 static const char* channel_names[] = {"B12", "B13", "B14", "B15", "A8 ", "A9 ", "A10", "A15", "B3 ", "B4 ", "B5 ", "B6 "}; /**< names of pin connected to target signals */
-static const uint32_t channel_rccs[] = {GPIO_RCC(PB12), GPIO_RCC(PB13), GPIO_RCC(PB14), GPIO_RCC(PB15), GPIO_RCC(PA8), GPIO_RCC(PA9), GPIO_RCC(PA10), GPIO_RCC(PA15), GPIO_RCC(PB3), GPIO_RCC(PB4), GPIO_RCC(PB5), GPIO_RCC(PB6)}; /**< RCC for signal pin ports */
 static const uint32_t channel_ports[] = {GPIO_PORT(PB12), GPIO_PORT(PB13), GPIO_PORT(PB14), GPIO_PORT(PB15), GPIO_PORT(PA8), GPIO_PORT(PA9), GPIO_PORT(PA10), GPIO_PORT(PA15), GPIO_PORT(PB3), GPIO_PORT(PB4), GPIO_PORT(PB5), GPIO_PORT(PB6)}; /**< GPIO ports for signal pin */
 static const uint32_t channel_pins[] = {GPIO_PIN(PB12), GPIO_PIN(PB13), GPIO_PIN(PB14), GPIO_PIN(PB15), GPIO_PIN(PA8), GPIO_PIN(PA9), GPIO_PIN(PA10), GPIO_PIN(PA15), GPIO_PIN(PB3), GPIO_PIN(PB4), GPIO_PIN(PB5), GPIO_PIN(PB6)}; /**< GPIO pins for signal pin */
 
@@ -111,6 +110,42 @@ static void print_fpu(double fpu, uint8_t precision)
 	puts(decimal);
 }
 
+/** get RCC from corresponding port
+ *  @param[in] port port address
+ *  @return RCC address corresponding to port
+ */
+static uint32_t port2rcc(uint32_t port)
+{
+	uint32_t rcc = 0;
+	switch (port) {
+	case GPIOA:
+		rcc = RCC_GPIOA;
+		break;
+	case GPIOB:
+		rcc = RCC_GPIOB;
+		break;
+	case GPIOC:
+		rcc = RCC_GPIOC;
+		break;
+	case GPIOD:
+		rcc = RCC_GPIOD;
+		break;
+	case GPIOE:
+		rcc = RCC_GPIOE;
+		break;
+	case GPIOF:
+		rcc = RCC_GPIOF;
+		break;
+	case GPIOG:
+		rcc = RCC_GPIOG;
+		break;
+	default: // unknown port
+		while (true); // halt firmware
+		break;
+	}
+	return rcc;
+}
+
 /** measure target and signal voltages
  *  @return voltages of channels
  */
@@ -759,7 +794,7 @@ void main(void)
 
 	puts("setup signal pins: ");
 	for (uint8_t i = 0; i < CHANNEL_NUMBERS; i++) {
-		rcc_periph_clock_enable(channel_rccs[i]); // enable clock for port domain
+		rcc_periph_clock_enable(port2rcc(channel_ports[i])); // enable clock for port domain
 		gpio_mode_setup(channel_ports[i], GPIO_MODE_INPUT, GPIO_PUPD_NONE, channel_pins[i]); // ensure pin is floating input
 	}
 	puts("OK\n");