diff --git a/src/lpc176x/gpio.c b/src/lpc176x/gpio.c
index 49363d2a..5f5f9375 100644
--- a/src/lpc176x/gpio.c
+++ b/src/lpc176x/gpio.c
@@ -32,6 +32,20 @@ static LPC_GPIO_TypeDef * const digital_regs[] = {
  * General Purpose Input Output (GPIO) pins
  ****************************************************************/
 
+// Enable a peripheral clock
+void
+enable_peripheral_clock(uint32_t pclk)
+{
+    LPC_SC->PCONP |= 1<<pclk;
+    if (pclk < 16) {
+        uint32_t shift = pclk * 2;
+        LPC_SC->PCLKSEL0 = (LPC_SC->PCLKSEL0 & ~(0x3<<shift)) | (0x1<<shift);
+    } else {
+        uint32_t shift = (pclk - 16) * 2;
+        LPC_SC->PCLKSEL1 = (LPC_SC->PCLKSEL1 & ~(0x3<<shift)) | (0x1<<shift);
+    }
+}
+
 // Set the mode and extended function of a pin
 void
 gpio_peripheral(int bank, int pin, int func, int pullup)
@@ -178,10 +192,9 @@ gpio_adc_setup(uint8_t pin)
 
     uint32_t prescal = DIV_ROUND_UP(CONFIG_CLOCK_FREQ*4, ADC_FREQ_MAX) - 1;
     uint32_t adcr = (1<<21) | ((prescal & 0xff) << 8);
-    if (!(LPC_SC->PCONP & (1<<12))) {
+    if (!(LPC_SC->PCONP & (1<<PCLK_ADC))) {
         // Power up ADC
-        LPC_SC->PCONP |= 1<<12;
-        LPC_SC->PCLKSEL0 = (LPC_SC->PCLKSEL0 & ~(0x3<<24)) | (0x1<<24);
+        enable_peripheral_clock(PCLK_ADC);
         LPC_ADC->ADCR = adcr;
     }
 
diff --git a/src/lpc176x/internal.h b/src/lpc176x/internal.h
index da1f169f..1ea07df4 100644
--- a/src/lpc176x/internal.h
+++ b/src/lpc176x/internal.h
@@ -2,6 +2,10 @@
 #define __LPC176X_INTERNAL_H
 // Local definitions for lpc176x code
 
+#define PCLK_TIMER0 1
+#define PCLK_UART0 3
+#define PCLK_ADC 12
+void enable_peripheral_clock(uint32_t pclk);
 void gpio_peripheral(int bank, int pin, int func, int pullup);
 
 #endif // internal.h
diff --git a/src/lpc176x/serial.c b/src/lpc176x/serial.c
index 7f2a0db9..1594a2ad 100644
--- a/src/lpc176x/serial.c
+++ b/src/lpc176x/serial.c
@@ -16,7 +16,7 @@ serial_init(void)
 {
     // Setup baud
     LPC_UART0->LCR = (1<<7); // set DLAB bit
-    LPC_SC->PCLKSEL0 = (LPC_SC->PCLKSEL0 & ~(0x3<<6)) | (0x1<<6);
+    enable_peripheral_clock(PCLK_UART0);
     uint32_t pclk = SystemCoreClock;
     uint32_t div = pclk / (CONFIG_SERIAL_BAUD * 16);
     LPC_UART0->DLL = div & 0xff;
diff --git a/src/lpc176x/timer.c b/src/lpc176x/timer.c
index 1b966d1c..318e8bea 100644
--- a/src/lpc176x/timer.c
+++ b/src/lpc176x/timer.c
@@ -8,6 +8,7 @@
 #include "board/irq.h" // irq_disable
 #include "board/misc.h" // timer_read_time
 #include "board/timer_irq.h" // timer_dispatch_many
+#include "internal.h" // enable_peripheral_clock
 #include "sched.h" // DECL_INIT
 
 // Set the next irq time
@@ -38,7 +39,7 @@ timer_init(void)
     // Disable timer
     LPC_TIM0->TCR = 0x02;
     // Setup clock and prescaler (divide sys clock by 4)
-    LPC_SC->PCLKSEL0 = (LPC_SC->PCLKSEL0 & ~(0x3<<2)) | (0x1<<2);
+    enable_peripheral_clock(PCLK_TIMER0);
     LPC_TIM0->PR = 3;
     // Enable interrupts
     NVIC_SetPriority(TIMER0_IRQn, 2);