[NUCLEO_L152RE] Add sleep api

Author: bcostm

libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/sleep.c

@@ -30,17 +30,97 @@
 #include "sleep_api.h"
 #include "cmsis.h"
 
+static void SetSysClock_HSI(void)
+{
+  __IO uint32_t StartUpCounter = 0, HSIStatus = 0;
+  
+  /* SYSCLK, HCLK, PCLK2 and PCLK1 configuration ---------------------------*/
+  /* Enable HSI */
+  RCC->CR |= ((uint32_t)RCC_CR_HSION);
+ 
+  /* Wait till HSI is ready and if Time out is reached exit */
+  do
+  {
+    HSIStatus = RCC->CR & RCC_CR_HSIRDY;
+  } while((HSIStatus == 0) && (StartUpCounter != HSI_STARTUP_TIMEOUT));
+
+  if ((RCC->CR & RCC_CR_HSIRDY) != RESET)
+  {
+    HSIStatus = (uint32_t)0x01;
+  }
+  else
+  {
+    HSIStatus = (uint32_t)0x00;
+  }
+    
+  if (HSIStatus == (uint32_t)0x01)
+  {
+    /* Flash 0 wait state */
+    FLASH->ACR &= ~FLASH_ACR_LATENCY;
+    
+    /* Disable Prefetch Buffer */
+    FLASH->ACR &= ~FLASH_ACR_PRFTEN;
+
+    /* Disable 64-bit access */
+    FLASH->ACR &= ~FLASH_ACR_ACC64;
+    
+    /* Power enable */
+    RCC->APB1ENR |= RCC_APB1ENR_PWREN;
+  
+    /* Select the Voltage Range 1 (1.8 V) */
+    PWR->CR = PWR_CR_VOS_0;
+  
+    /* Wait Until the Voltage Regulator is ready */
+    while((PWR->CSR & PWR_CSR_VOSF) != RESET)
+    {
+    }
+      
+    /* HCLK = SYSCLK /1*/
+    RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;
+    /* PCLK2 = HCLK /1*/
+    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;
+    
+    /* PCLK1 = HCLK /1*/
+    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV1;
+    
+    /* Select HSI as system clock source */
+    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
+    RCC->CFGR |= (uint32_t)RCC_CFGR_SW_HSI;
+
+    /* Wait till HSI is used as system clock source */
+    while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)RCC_CFGR_SWS_HSI)
+    {
+    }
+  }
+  else
+  {
+    /* If HSI fails to start-up, the application will have wrong clock
+       configuration. User can add here some code to deal with this error */
+  }
+}
+
+// MCU SLEEP mode
 void sleep(void)
 {
-    SCB->SCR = 0; // Normal sleep mode for ARM core
-    __WFI();
+    // Enable PWR clock
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);    
+    // Request to enter SLEEP mode with regulator ON
+    PWR_EnterSleepMode(PWR_Regulator_ON, PWR_SLEEPEntry_WFI); 
 }
 
+// MCU STOP mode (Regulator in LP mode, LSI, HSI and HSE OFF)
 void deepsleep(void)
 {    
     // Enable PWR clock
     RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);
 
-    // Request to enter STOP mode with regulator in low power mode
+    // Enable Ultra low power mode
+    PWR_UltraLowPowerCmd(ENABLE);
+
+    // Enter Stop Mode
     PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);  
+  
+    // After wake-up from STOP reconfigure the system clock (HSI)
+    SetSysClock_HSI();
+      
 }