Added LF clock starting code to SysInit.

Author: anangl

hal/targets/cmsis/TARGET_NORDIC/TARGET_NRF5/TARGET_MCU_NRF51822/system_nrf51.c

@@ -94,6 +94,16 @@ void SystemInit(void)
         }
         *(uint32_t volatile *)0x4006EC14 = 0xC0;
     }
+
+    // Start the external 32khz crystal oscillator.
+    NRF_CLOCK->LFCLKSRC             = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos);
+    NRF_CLOCK->EVENTS_LFCLKSTARTED  = 0;
+    NRF_CLOCK->TASKS_LFCLKSTART     = 1;
+
+    // Wait for the external oscillator to start up.
+    while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0) {
+        // Do nothing.
+    }
 }
 
 

hal/targets/cmsis/TARGET_NORDIC/TARGET_NRF5/TARGET_MCU_NRF52832/system_nrf52.c

@@ -187,6 +187,16 @@ void SystemInit(void)
     #endif
 
     SystemCoreClockUpdate();
+
+    // Start the external 32khz crystal oscillator.
+    NRF_CLOCK->LFCLKSRC             = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos);
+    NRF_CLOCK->EVENTS_LFCLKSTARTED  = 0;
+    NRF_CLOCK->TASKS_LFCLKSTART     = 1;
+
+    // Wait for the external oscillator to start up.
+    while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0) {
+        // Do nothing.
+    }
 }