diff --git a/sw/airborne/arch/stm32/mcu_arch.c b/sw/airborne/arch/stm32/mcu_arch.c
index d7e3a81370..9a3c84f27e 100644
--- a/sw/airborne/arch/stm32/mcu_arch.c
+++ b/sw/airborne/arch/stm32/mcu_arch.c
@@ -27,69 +27,19 @@
 #include BOARD_CONFIG
 
 #include <inttypes.h>
-#include <stm32/gpio.h>
-#include <stm32/rcc.h>
-#include <stm32/flash.h>
-#include <stm32/misc.h>
+#include <libopencm3/stm32/f1/gpio.h>
 #include <libopencm3/stm32/f1/rcc.h>
+#include <libopencm3/stm32/f1/flash.h>
 
 void mcu_arch_init(void) {
-#if USE_OPENCM3
+#if EXT_CLK == 8000000
+#pragma message "Using 8MHz external clock to PLL it to 72MHz."
+  rcc_clock_setup_in_hse_8mhz_out_72mhz();
+#elif EXT_CLK == 12000000
+#pragma message "Using 12MHz external clock to PLL it to 72MHz."
   rcc_clock_setup_in_hse_12mhz_out_72mhz();
-  NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
-  return;
-#else // !USE_OPENCM3
-#ifdef HSE_TYPE_EXT_CLK
-#pragma message "Using external clock."
-  /* Setup the microcontroller system.
-   *  Initialize the Embedded Flash Interface,
-   *  initialize the PLL and update the SystemFrequency variable.
-   */
-  /* RCC system reset(for debug purpose) */
-  RCC_DeInit();
-  /* Enable HSE with external clock ( HSE_Bypass ) */
-  RCC_HSEConfig( STM32_RCC_MODE );
-  /* Wait till HSE is ready */
-  ErrorStatus HSEStartUpStatus = RCC_WaitForHSEStartUp();
-  if (HSEStartUpStatus != SUCCESS) {
-    /* block if something went wrong */
-    while(1) {}
-  }
-  else {
-    /* Enable Prefetch Buffer */
-    FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
-    /* Flash 2 wait state */
-    FLASH_SetLatency(FLASH_Latency_2);
-    /* HCLK = SYSCLK */
-    RCC_HCLKConfig(RCC_SYSCLK_Div1);
-    /* PCLK2 = HCLK */
-    RCC_PCLK2Config(RCC_HCLK_Div1);
-    /* PCLK1 = HCLK/2 */
-    RCC_PCLK1Config(RCC_HCLK_Div2);
-    /* PLLCLK = 8MHz * 9 = 72 MHz */
-    RCC_PLLConfig(RCC_PLLSource_HSE_Div1, STM32_PLL_MULT);
-    /* Enable PLL */
-    RCC_PLLCmd(ENABLE);
-    /* Wait till PLL is ready */
-    while (RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET) {}
-    /* Select PLL as system clock source */
-    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
-    /* Wait till PLL is used as system clock source */
-    while(RCC_GetSYSCLKSource() != 0x08) {}
-  }
-#else  /* HSE_TYPE_EXT_CLK */
-#pragma message "Using normal system clock setup."
-  SystemInit();
-#endif /* HSE_TYPE_EXT_CLK */
-   /* Set the Vector Table base location at 0x08000000 */
-  NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
-
-#ifdef STM32_FORCE_ALL_CLOCK_ON
-  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |
-                         RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOD |
-                         RCC_APB2Periph_GPIOE | RCC_APB2Periph_AFIO, ENABLE);
+#else
+#error EXT_CLK is either set to an unsupported frequency or not defined at all. Please check!
 #endif
-
-#endif // USE_OPENCM3
 }
 
diff --git a/sw/airborne/boards/lisa_l_1.0.h b/sw/airborne/boards/lisa_l_1.0.h
index 5cf7ef8e27..e9652741ad 100644
--- a/sw/airborne/boards/lisa_l_1.0.h
+++ b/sw/airborne/boards/lisa_l_1.0.h
@@ -3,13 +3,10 @@
 
 #define BOARD_LISA_L
 
+/* Lisa/L has an 8MHZ external clock and 72MHz internal. */
+#define EXT_CLK 8000000
 #define AHB_CLK 72000000
 
-/* Lisa uses an external clock instead of a crystal */
-#define HSE_TYPE_EXT_CLK
-#define STM32_RCC_MODE RCC_HSE_Bypass
-#define STM32_PLL_MULT RCC_PLLMul_9
-
 /* Onboard LEDs */
 #define LED_1_BANK
 #define LED_STP08
diff --git a/sw/airborne/boards/lisa_m_1.0.h b/sw/airborne/boards/lisa_m_1.0.h
index 65c50d754d..de64b20a41 100644
--- a/sw/airborne/boards/lisa_m_1.0.h
+++ b/sw/airborne/boards/lisa_m_1.0.h
@@ -3,6 +3,8 @@
 
 #define BOARD_LISA_M
 
+/* Lisa/M has a 12MHz external clock and 72MHz internal. */
+#define EXT_CLK 12000000
 #define AHB_CLK 72000000
 
 /* Onboard LEDs */
diff --git a/sw/airborne/boards/olimex_stm32-h103.h b/sw/airborne/boards/olimex_stm32-h103.h
index f134c747f6..2ff19fb522 100644
--- a/sw/airborne/boards/olimex_stm32-h103.h
+++ b/sw/airborne/boards/olimex_stm32-h103.h
@@ -1,18 +1,14 @@
 #ifndef CONFIG_OLIMEX_STM32_H103_H
 #define CONFIG_OLIMEX_STM32_H103_H
 
-
+/* Olimex STM32-H103 board has an 8MHz external clock and 72MHz internal. */
+#define EXT_CLK 8000000
 #define AHB_CLK 72000000
 
-/* this board uses a crystal for HSE */
-//#define HSE_TYPE RCC_HSE_ON
-
 /* Onboard LEDs */
 #define LED_1_BANK
 #define LED_1_GPIO GPIOC
 #define LED_1_GPIO_CLK RCC_APB2Periph_GPIOC
 #define LED_1_GPIO_PIN GPIO_Pin_12
 
-
-
 #endif /* CONFIG_OLIMEX_STM32_H103_H */