Merge pull request #186 from lyusupov/REGOUT0

fix against pollution of REGOUT0 reserved bits

Author: hathach

src/boards/boards.c

@@ -94,11 +94,13 @@ void board_init(void)
 //     #define UICR_REGOUT0_VALUE UICR_REGOUT0_VOUT_3V3
 // in board.h when using that power configuration.
 #ifdef UICR_REGOUT0_VALUE
-  if (NRF_UICR->REGOUT0 != UICR_REGOUT0_VALUE) 
+  if ((NRF_UICR->REGOUT0 & UICR_REGOUT0_VOUT_Msk) !=
+      (UICR_REGOUT0_VALUE << UICR_REGOUT0_VOUT_Pos))
   {
       NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos;
       while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
-      NRF_UICR->REGOUT0 = UICR_REGOUT0_VALUE;
+      NRF_UICR->REGOUT0 = (NRF_UICR->REGOUT0 & ~((uint32_t)UICR_REGOUT0_VOUT_Msk)) |
+                          (UICR_REGOUT0_VALUE << UICR_REGOUT0_VOUT_Pos);
 
       NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos;
       while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}