diff --git a/cpu/cc2538/cpu.c b/cpu/cc2538/cpu.c
index 35203832e8..6011c614ab 100644
--- a/cpu/cc2538/cpu.c
+++ b/cpu/cc2538/cpu.c
@@ -18,23 +18,11 @@
  */
 
 #include <assert.h>
+#include "stdio_base.h"
 
 #include "cpu.h"
 #include "periph/init.h"
-#include "stdio_base.h"
-
-#define BIT(n)          ( 1UL << (n) )
-
-/* Select CLOCK_CTRL register bit masks: */
-#define OSC32K          BIT(24) /**< 32-kHz clock oscillator selection */
-#define OSC_PD          BIT(17) /**< Oscillator power-down */
-#define OSC             BIT(16) /**< System clock oscillator selection */
-
-/* CLOCK_CTRL register field offsets: */
-#define IO_DIV_SHIFT    8
-#define SYS_DIV_SHIFT   0
-
-#define CLOCK_STA_MASK ( OSC32K | OSC )
+#include "periph_conf.h"
 
 static void cpu_clock_init(void);
 
@@ -55,22 +43,14 @@ void cpu_init(void)
     periph_init();
 }
 
+
 /**
  * @brief Configure the controllers clock system
  */
 static void cpu_clock_init(void)
 {
-    const uint32_t CLOCK_CTRL_VALUE =
-        OSC_PD                  /**< Power down the oscillator not selected by OSC bit (hardware-controlled when selected). */
-        | (1 << IO_DIV_SHIFT)   /**< 16 MHz IO_DIV */
-        | (1 << SYS_DIV_SHIFT)  /**< 16 MHz SYS_DIV */
-#if !SYS_CTRL_OSC32K_USE_XTAL
-        | OSC32K                /**< Use internal RC oscillator. */
-#endif
-    ;
-
 #if SYS_CTRL_OSC32K_USE_XTAL
-    /* Set the XOSC32K_Q pads to analog for the external crystal: */
+    /* set the XOSC32K_Q pads to analog for the external crystal: */
     gpio_software_control(GPIO_PD6);
     gpio_dir_input(GPIO_PD6);
     IOC_PXX_OVER[GPIO_PD6] = IOC_OVERRIDE_ANA;
@@ -80,15 +60,41 @@ static void cpu_clock_init(void)
     IOC_PXX_OVER[GPIO_PD7] = IOC_OVERRIDE_ANA;
 #endif
 
-    /* Configure the clock settings: */
-    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRL = CLOCK_CTRL_VALUE;
-
-    /* Wait for the new clock settings to take effect: */
-    while ((SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STA ^ CLOCK_CTRL_VALUE) & CLOCK_STA_MASK);
+    /* CLOCK_CTRL.OSC32K register bit can be written at any time, but only takes
+       effect when 16MHz RCOSC is the active system clock source, 16MHz RCOSC is
+       the active clock on reset but to be idempotent make sure it's the
+       selected source clock */
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.OSC = 1;
+    while (SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SOURCE_CHANGE) {}
 
 #if SYS_CTRL_OSC32K_USE_XTAL
-    /* Wait for the 32-kHz crystal oscillator to stabilize: */
-    while ( SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SYNC_32K);
-    while (!SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SYNC_32K);
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.OSC32K = 0;
+    while (SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.OSC32K) {}
+#else
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.OSC32K = 1;
+    while (!SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.OSC32K) {}
+#endif
+
+#if SYS_CTRL_OSC_USE_XTAL
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.OSC = 0;
+#else
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.OSC = 1;
+#endif
+
+    /* power down the oscillator not selected by OSC bit */
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.OSC_PD = 1;
+    /* set desired system clock rate */
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.SYS_DIV = \
+        __builtin_ctz(XOSC32M_FREQ / CLOCK_CORECLOCK);
+    /* set desired I/O clock rate */
+    SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRLbits.IO_DIV = \
+        __builtin_ctz(XOSC32M_FREQ / CLOCK_IO);
+    /* wait for new clock settings to take effect */
+    while (SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SOURCE_CHANGE) {}
+
+#if SYS_CTRL_OSC32K_USE_XTAL
+    /* 32-kHz crystal oscillator to stabilize after a positive transition */
+    while (SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SYNC_32K) {}
+    while (!SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SYNC_32K) {}
 #endif
 }
diff --git a/cpu/cc2538/include/cc2538.h b/cpu/cc2538/include/cc2538.h
index 6f97718a17..5088eec238 100644
--- a/cpu/cc2538/include/cc2538.h
+++ b/cpu/cc2538/include/cc2538.h
@@ -798,10 +798,14 @@ typedef volatile uint32_t cc2538_reg_t; /**< Least-significant 32 bits of the IE
 #define CCTEST_USBCTRL              ( *(cc2538_reg_t*)0x44010050 ) /**< CCTEST USB PHY stand-by control */
 /** @} */
 
-#define XOSC32M_FREQ                32000000 /**< 32 MHz external oscillator/clock frequency */
-#define RCOSC16M_FREQ               16000000 /**< 16 MHz internal RC oscillator frequency */
+#define XOSC32M_FREQ                32000000U /**< 32 MHz external oscillator/clock frequency */
+#define RCOSC16M_FREQ               16000000U /**< 16 MHz internal RC oscillator frequency */
 
-#define CC2538_VTOR_ALIGN                512 /**< CC2538 Vector Table alignment */
+#define XOSC32K_FREQ                   32768U /**< 32 KHz external oscillator/clock frequency */
+#define RCOSC32K_FREQ                  32753U /**< 32 KHz internal RC oscillator frequency */
+
+
+#define CC2538_VTOR_ALIGN                 512 /**< CC2538 Vector Table alignment */
 
 #ifdef __cplusplus
 }