From 556de14a1db07ae67a96a4c4a27f8a04b9082967 Mon Sep 17 00:00:00 2001
From: Richard Barry <ribarry@amazon.com>
Date: Mon, 1 Feb 2016 18:04:50 +0000
Subject: [PATCH] Update EFM32 demos to include an option to use the RTC as the
 clock source when using low power tickless mode.

---
 .../.cproject                                 |   5 +-
 .../Source/FreeRTOSConfig.h                   |  78 +++-
 .../Source/Full_Demo/main_full.c              |   5 +-
 ...nt.c => low_power_tick_management_BURTC.c} |  20 +-
 .../low_power_tick_management_RTC.c           | 341 ++++++++++++++++++
 .../Source/Low_Power_Demo/main_low_power.c    |   9 +-
 .../Source/main.c                             |  16 +-
 7 files changed, 434 insertions(+), 40 deletions(-)
 rename FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/{low_power_tick_management.c => low_power_tick_management_BURTC.c} (93%)
 create mode 100644 FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management_RTC.c

diff --git a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/.cproject b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/.cproject
index f474883a1..7529f4923 100644
--- a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/.cproject
+++ b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/.cproject
@@ -53,7 +53,7 @@
 									<listOptionValue builtIn="false" value="&quot;${workspace_loc:/${ProjName}/Source/SilLabs_Code/kits/EFM32GG_STK3700/config}&quot;"/>
 									<listOptionValue builtIn="false" value="&quot;${workspace_loc:/${ProjName}/Source/SilLabs_Code/Device/SiliconLabs/EFM32GG/Include}&quot;"/>
 								</option>
-								<option id="gnu.c.compiler.option.preprocessor.undef.symbol.1550566013" name="Undefined symbols (-U)" superClass="gnu.c.compiler.option.preprocessor.undef.symbol" valueType="undefDefinedSymbols"/>
+								<option id="gnu.c.compiler.option.preprocessor.undef.symbol.1550566013" name="Undefined symbols (-U)" superClass="gnu.c.compiler.option.preprocessor.undef.symbol"/>
 								<inputType id="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.c.compiler.input.733848972" superClass="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.c.compiler.input"/>
 							</tool>
 							<tool id="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.cpp.compiler.base.1840601111" name="GNU ARM C++ Compiler" superClass="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.cpp.compiler.base">
@@ -103,6 +103,9 @@
 							<tool id="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.archiver.base.1920617400" name="GNU ARM Archiver" superClass="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.archiver.base"/>
 						</toolChain>
 					</folderInfo>
+					<fileInfo id="com.silabs.ide.si32.gcc.debug#com.silabs.ide.si32.gcc:4.8.3.20131129.566130702" name="low_power_tick_management_BURTC.c" rcbsApplicability="disable" resourcePath="Source/Low_Power_Demo/low_power_tick_management_BURTC.c" toolsToInvoke="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.c.compiler.base.1299820402.669016646">
+						<tool id="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.c.compiler.base.1299820402.669016646" name="GNU ARM C Compiler" superClass="com.silabs.ide.si32.gcc.cdt.managedbuild.tool.gnu.c.compiler.base.1299820402"/>
+					</fileInfo>
 					<sourceEntries>
 						<entry excluding="Source/FreeRTOS_Source/portable/GCC/ARM_CM4F|Source/SilLabs_Code/kits/EFM32WG_STK3800|Source/SilLabs_Code/Device/SiliconLabs/EFM32GG/Source|Source/SilLabs_Code/Device/SiliconLabs/EFM32WG|Source/SilLabs_Code/CMSIS/efm32wg|CMSIS/efm32wg|Source/SilLabs_Code/kits/bsp/bsp_dk_3201.c|Source/SilLabs_Code/kits/bsp/bsp_dk_3200.c|Source/SilLabs_Code/kits/bsp/bsp_dk_leds.c|Source/RTT|Source/SilLabs_Code/kits/bsp/bsp_dk_mcuboard.c|Source/SilLabs_Code/kits/bsp/bsp_bcc.c" flags="VALUE_WORKSPACE_PATH|RESOLVED" kind="sourcePath" name=""/>
 					</sourceEntries>
diff --git a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/FreeRTOSConfig.h b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/FreeRTOSConfig.h
index 8c9f5192b..e0f66cd52 100644
--- a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/FreeRTOSConfig.h
+++ b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/FreeRTOSConfig.h
@@ -87,28 +87,24 @@ extern "C" {
  *----------------------------------------------------------*/
 
 
-/* Set configCREATE_LOW_POWER_DEMO to one to run the simple blinky demo low power
-example, or 1 to run the more comprehensive test and demo application.  See
-the comments at the top of main.c for more information. */
-#define configCREATE_LOW_POWER_DEMO	1
+/* Set configCREATE_LOW_POWER_DEMO as follows:
+ *
+ * 0: Build the full test and demo application.
+ * 1: Build the simple blinky tickless low power demo, generating the tick
+ *    interrupt from the BURTC.  EM3 will be entered, but use of the ULFRCO
+ *    clock means timing will be inaccurate.
+ * 2: Build the simple blinky tickless low power demo, generating the tick from
+ *    the RTC.  EM2 will be entered.  The LXFO clock is used, which is more
+ *    accurate than the ULFRCO clock.
+ *  See the comments at the top of main.c, main_full.c and main_low_power.c for
+ *  more information.
+ */
+#define configCREATE_LOW_POWER_DEMO	2
 
 /* Some configuration is dependent on the demo being built. */
-#if( configCREATE_LOW_POWER_DEMO == 1 )
+#if( configCREATE_LOW_POWER_DEMO == 0 )
 
-	/* The slow clock used to generate the tick interrupt in the low power demo
-	runs at 32768Hz.  Ensure the clock is a multiple of the tick rate. */
-	#define configTICK_RATE_HZ				( 100 )
-
-	/* The low power demo uses the tickless idle feature. */
-	#define configUSE_TICKLESS_IDLE			1
-
-	/* Hook function related definitions. */
-	#define configUSE_TICK_HOOK				( 0 )
-	#define configCHECK_FOR_STACK_OVERFLOW	( 0 )
-	#define configUSE_MALLOC_FAILED_HOOK	( 0 )
-	#define configUSE_IDLE_HOOK				( 0 )
-
-#else
+	/* Tickless mode is not used. */
 
 	/* Some of the standard demo test tasks assume a tick rate of 1KHz, even
 	though that is faster than would normally be warranted by a real
@@ -124,7 +120,49 @@ the comments at the top of main.c for more information. */
 	#define configUSE_TICK_HOOK				( 1 )
 	#define configCHECK_FOR_STACK_OVERFLOW	( 1 )
 	#define configUSE_MALLOC_FAILED_HOOK	( 1 )
-	#define configUSE_IDLE_HOOK  ( 1 )
+	#define configUSE_IDLE_HOOK  			( 1 )
+
+	#define configENERGY_MODE				( sleepEM3 )
+
+#elif( configCREATE_LOW_POWER_DEMO == 1 )
+
+	/* Tickless idle mode, generating RTOS tick interrupts from the BURTC, fed
+	by the [inaccurate] ULFRCO clock. */
+
+	/* The slow clock used to generate the tick interrupt in the low power demo
+	runs at 2KHz.  Ensure the tick rate is a multiple of the clock. */
+	#define configTICK_RATE_HZ				( 100 )
+
+	/* The low power demo uses the tickless idle feature. */
+	#define configUSE_TICKLESS_IDLE			1
+
+	/* Hook function related definitions. */
+	#define configUSE_TICK_HOOK				( 0 )
+	#define configCHECK_FOR_STACK_OVERFLOW	( 0 )
+	#define configUSE_MALLOC_FAILED_HOOK	( 0 )
+	#define configUSE_IDLE_HOOK				( 0 )
+
+	#define configENERGY_MODE				( sleepEM4 )
+
+#elif( configCREATE_LOW_POWER_DEMO == 2 )
+
+	/* Tickless idle mode, generating RTOS tick interrupts from the RTC, fed
+	by the LXFO clock. */
+
+	/* The slow clock used to generate the tick interrupt in the low power demo
+	runs at 32768/8=4096Hz.  Ensure the tick rate is a multiple of the clock. */
+	#define configTICK_RATE_HZ				( 128 )
+
+	/* The low power demo uses the tickless idle feature. */
+	#define configUSE_TICKLESS_IDLE			1
+
+	/* Hook function related definitions. */
+	#define configUSE_TICK_HOOK				( 0 )
+	#define configCHECK_FOR_STACK_OVERFLOW	( 0 )
+	#define configUSE_MALLOC_FAILED_HOOK	( 0 )
+	#define configUSE_IDLE_HOOK				( 0 )
+
+	#define configENERGY_MODE				( sleepEM3 )
 
 #endif
 
diff --git a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Full_Demo/main_full.c b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Full_Demo/main_full.c
index 4d1dc0a5a..83e33d953 100644
--- a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Full_Demo/main_full.c
+++ b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Full_Demo/main_full.c
@@ -71,8 +71,9 @@
  * NOTE 1:  This project provides two demo applications.  A simple blinky style
  * project that demonstrates the tickless low power features of FreeRTOS, and a
  * more comprehensive test and demo application.  The configCREATE_LOW_POWER_DEMO
- * setting in FreeRTOSConifg.h is used to select between the two.  See the notes
- * on using conifgCREATE_LOW_POWER_DEMO in main.c.  This file implements the
+ * setting in FreeRTOSConifg.h is used to select between the two, and to select
+ * the clock used when tickless mode is used.  See the notes on using
+ * conifgCREATE_LOW_POWER_DEMO in main.c.  This file implements the
  * comprehensive test and demo version.
  *
  * NOTE 2:  This file only contains the source code that is specific to the
diff --git a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management.c b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management_BURTC.c
similarity index 93%
rename from FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management.c
rename to FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management_BURTC.c
index e7ab76250..6f3e38085 100644
--- a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management.c
+++ b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management_BURTC.c
@@ -83,7 +83,9 @@
 #include "em_int.h"
 #include "sleep.h"
 
-/* This file contains functions that will override the default implementations
+/* SEE THE COMMENTS ABOVE THE DEFINITION OF configCREATE_LOW_POWER_DEMO IN
+FreeRTOSConfig.h
+This file contains functions that will override the default implementations
 in the RTOS port layer.  Therefore only build this file if the low power demo
 is being built. */
 #if( configCREATE_LOW_POWER_DEMO == 1 )
@@ -98,7 +100,8 @@ is being built. */
  */
 void vPortSetupTimerInterrupt( void );
 
-/* Override the default definition of vPortSuppressTicksAndSleep() that is
+/*
+ * Override the default definition of vPortSuppressTicksAndSleep() that is
  * weakly defined in the FreeRTOS Cortex-M port layer with a version that
  * manages the BURTC clock, as the tick is generated from the low power BURTC
  * and not the SysTick as would normally be the case on a Cortex-M.
@@ -110,12 +113,11 @@ void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime );
 /* Calculate how many clock increments make up a single tick period. */
 static const uint32_t ulReloadValueForOneTick = ( mainTIMER_FREQUENCY_HZ / configTICK_RATE_HZ );
 
-/* Calculate the maximum number of ticks that can be suppressed when using the
-high resolution clock and low resolution clock respectively. */
+/* Will hold the maximum number of ticks that can be suppressed. */
 static uint32_t xMaximumPossibleSuppressedTicks = 0;
 
 /* Flag set from the tick interrupt to allow the sleep processing to know if
-sleep mode was exited because of an timer interrupt or a different interrupt. */
+sleep mode was exited because of a timer interrupt or a different interrupt. */
 static volatile uint32_t ulTickFlag = pdFALSE;
 
 /* As the clock is only 2KHz, it is likely a value of 1 will be too much, so
@@ -129,6 +131,8 @@ void vPortSetupTimerInterrupt( void )
 {
 BURTC_Init_TypeDef xBURTCInitStruct = BURTC_INIT_DEFAULT;
 
+	/* Configure the BURTC to generate the RTOS tick interrupt. */
+
 	xMaximumPossibleSuppressedTicks = ULONG_MAX / ulReloadValueForOneTick;
 
 	/* Ensure LE modules are accessible. */
@@ -145,7 +149,7 @@ BURTC_Init_TypeDef xBURTCInitStruct = BURTC_INIT_DEFAULT;
 	BURTC_IntDisable( BURTC_IF_COMP0 );
 	BURTC_Init( &xBURTCInitStruct );
 
-	/* The tick interrupt must be set to the lowest possible. */
+	/* The tick interrupt must be set to the lowest priority possible. */
 	NVIC_SetPriority( BURTC_IRQn, configKERNEL_INTERRUPT_PRIORITY );
 	NVIC_ClearPendingIRQ( BURTC_IRQn );
 	NVIC_EnableIRQ( BURTC_IRQn );
@@ -299,11 +303,11 @@ TickType_t xModifiableIdleTime;
 }
 /*-----------------------------------------------------------*/
 
-void BURTC_IRQHandler(void)
+void BURTC_IRQHandler( void )
 {
 	if( ulTickFlag == pdFALSE )
 	{
-		/* Set BURTC interrupt to one system tick period*/
+		/* Set BURTC interrupt to one RTOS tick period. */
 		BURTC_Enable( false );
 		BURTC_CompareSet( 0, ulReloadValueForOneTick );
 		ulTickFlag = pdTRUE;
diff --git a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management_RTC.c b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management_RTC.c
new file mode 100644
index 000000000..d736f2670
--- /dev/null
+++ b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/low_power_tick_management_RTC.c
@@ -0,0 +1,341 @@
+/*
+    FreeRTOS V8.2.3 - Copyright (C) 2015 Real Time Engineers Ltd.
+    All rights reserved
+
+    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
+
+    This file is part of the FreeRTOS distribution.
+
+    FreeRTOS is free software; you can redistribute it and/or modify it under
+    the terms of the GNU General Public License (version 2) as published by the
+    Free Software Foundation >>>> AND MODIFIED BY <<<< the FreeRTOS exception.
+
+    ***************************************************************************
+    >>!   NOTE: The modification to the GPL is included to allow you to     !<<
+    >>!   distribute a combined work that includes FreeRTOS without being   !<<
+    >>!   obliged to provide the source code for proprietary components     !<<
+    >>!   outside of the FreeRTOS kernel.                                   !<<
+    ***************************************************************************
+
+    FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+    FOR A PARTICULAR PURPOSE.  Full license text is available on the following
+    link: http://www.freertos.org/a00114.html
+
+    ***************************************************************************
+     *                                                                       *
+     *    FreeRTOS provides completely free yet professionally developed,    *
+     *    robust, strictly quality controlled, supported, and cross          *
+     *    platform software that is more than just the market leader, it     *
+     *    is the industry's de facto standard.                               *
+     *                                                                       *
+     *    Help yourself get started quickly while simultaneously helping     *
+     *    to support the FreeRTOS project by purchasing a FreeRTOS           *
+     *    tutorial book, reference manual, or both:                          *
+     *    http://www.FreeRTOS.org/Documentation                              *
+     *                                                                       *
+    ***************************************************************************
+
+    http://www.FreeRTOS.org/FAQHelp.html - Having a problem?  Start by reading
+    the FAQ page "My application does not run, what could be wrong?".  Have you
+    defined configASSERT()?
+
+    http://www.FreeRTOS.org/support - In return for receiving this top quality
+    embedded software for free we request you assist our global community by
+    participating in the support forum.
+
+    http://www.FreeRTOS.org/training - Investing in training allows your team to
+    be as productive as possible as early as possible.  Now you can receive
+    FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
+    Ltd, and the world's leading authority on the world's leading RTOS.
+
+    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
+    including FreeRTOS+Trace - an indispensable productivity tool, a DOS
+    compatible FAT file system, and our tiny thread aware UDP/IP stack.
+
+    http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
+    Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
+
+    http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
+    Integrity Systems ltd. to sell under the OpenRTOS brand.  Low cost OpenRTOS
+    licenses offer ticketed support, indemnification and commercial middleware.
+
+    http://www.SafeRTOS.com - High Integrity Systems also provide a safety
+    engineered and independently SIL3 certified version for use in safety and
+    mission critical applications that require provable dependability.
+
+    1 tab == 4 spaces!
+*/
+
+/* FreeRTOS includes. */
+#include "FreeRTOS.h"
+#include "task.h"
+
+/* SiLabs library includes. */
+#include "em_cmu.h"
+#include "em_rtc.h"
+#include "em_rmu.h"
+#include "em_int.h"
+#include "sleep.h"
+
+/* SEE THE COMMENTS ABOVE THE DEFINITION OF configCREATE_LOW_POWER_DEMO IN
+FreeRTOSConfig.h
+This file contains functions that will override the default implementations
+in the RTOS port layer.  Therefore only build this file if the low power demo
+is being built. */
+#if( configCREATE_LOW_POWER_DEMO == 2 )
+
+#define mainTIMER_FREQUENCY_HZ	( 4096UL ) /* 32768 clock divided by 8. */
+
+/*
+ * The low power demo does not use the SysTick, so override the
+ * vPortSetupTickInterrupt() function with an implementation that configures
+ * a low power clock source.  NOTE:  This function name must not be changed as
+ * it is called from the RTOS portable layer.
+ */
+void vPortSetupTimerInterrupt( void );
+
+/*
+ * Override the default definition of vPortSuppressTicksAndSleep() that is
+ * weakly defined in the FreeRTOS Cortex-M port layer with a version that
+ * manages the RTC clock, as the tick is generated from the low power RTC
+ * and not the SysTick as would normally be the case on a Cortex-M.
+ */
+void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime );
+
+/*-----------------------------------------------------------*/
+
+/* Calculate how many clock increments make up a single tick period. */
+static const uint32_t ulReloadValueForOneTick = ( mainTIMER_FREQUENCY_HZ / configTICK_RATE_HZ );
+
+/* Will hold the maximum number of ticks that can be suppressed. */
+static uint32_t xMaximumPossibleSuppressedTicks = 0;
+
+/* Flag set from the tick interrupt to allow the sleep processing to know if
+sleep mode was exited because of a timer interrupt or a different interrupt. */
+static volatile uint32_t ulTickFlag = pdFALSE;
+
+/* As the clock is only 32KHz, it is likely a value of 1 will be enough. */
+static const uint32_t ulStoppedTimerCompensation = 0UL;
+
+/*-----------------------------------------------------------*/
+
+void vPortSetupTimerInterrupt( void )
+{
+RTC_Init_TypeDef xRTCInitStruct;
+const uint32_t ulMAX24BitValue = 0xffffffUL;
+
+	xMaximumPossibleSuppressedTicks = ulMAX24BitValue / ulReloadValueForOneTick;
+
+	/* Configure the RTC to generate the RTOS tick interrupt. */
+
+	/* LXFO setup.  For rev D use 70% boost */
+	CMU->CTRL = ( CMU->CTRL & ~_CMU_CTRL_LFXOBOOST_MASK ) | CMU_CTRL_LFXOBOOST_70PCENT;
+	#if defined( EMU_AUXCTRL_REDLFXOBOOST )
+		EMU->AUXCTRL = (EMU->AUXCTRL & ~_EMU_AUXCTRL_REDLFXOBOOST_MASK) | EMU_AUXCTRL_REDLFXOBOOST;
+	#endif
+
+	/* Ensure LE modules are accessible. */
+	CMU_ClockEnable( cmuClock_CORELE, true );
+
+	/* Use LFXO. */
+	CMU_ClockSelectSet( cmuClock_LFA, cmuSelect_LFXO );
+
+	/* Use 8x divider to reduce energy. */
+	CMU_ClockDivSet( cmuClock_RTC, cmuClkDiv_8 );
+
+	/* Enable clock to the RTC module. */
+	CMU_ClockEnable( cmuClock_RTC, true );
+	xRTCInitStruct.enable = false;
+	xRTCInitStruct.debugRun = false;
+	xRTCInitStruct.comp0Top = true;
+	RTC_Init( &xRTCInitStruct );
+
+	/* Disable RTC0 interrupt. */
+	RTC_IntDisable( RTC_IFC_COMP0 );
+
+	/* The tick interrupt must be set to the lowest priority possible. */
+	NVIC_SetPriority( RTC_IRQn, configKERNEL_INTERRUPT_PRIORITY );
+	NVIC_ClearPendingIRQ( RTC_IRQn );
+	NVIC_EnableIRQ( RTC_IRQn );
+	RTC_CompareSet( 0, ulReloadValueForOneTick );
+	RTC_IntClear( RTC_IFC_COMP0 );
+	RTC_IntEnable( RTC_IF_COMP0 );
+	RTC_Enable( true );
+}
+/*-----------------------------------------------------------*/
+
+void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
+{
+uint32_t ulReloadValue, ulCompleteTickPeriods, ulCurrentCount;
+eSleepModeStatus eSleepAction;
+TickType_t xModifiableIdleTime;
+
+	/* THIS FUNCTION IS CALLED WITH THE SCHEDULER SUSPENDED. */
+
+	/* Make sure the RTC reload value does not overflow the counter. */
+	if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
+	{
+		xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
+	}
+
+	/* Calculate the reload value required to wait xExpectedIdleTime tick
+	periods. */
+	ulReloadValue = ulReloadValueForOneTick * xExpectedIdleTime;
+	if( ulReloadValue > ulStoppedTimerCompensation )
+	{
+		/* Compensate for the fact that the RTC is going to be stopped
+		momentarily. */
+		ulReloadValue -= ulStoppedTimerCompensation;
+	}
+
+	/* Stop the RTC momentarily.  The time the RTC is stopped for is accounted
+	for as best it can be, but using the tickless mode will inevitably result
+	in some tiny drift of the time maintained by the kernel with respect to
+	calendar time.  The count is latched before stopping the timer as stopping
+	the timer appears to clear the count. */
+	ulCurrentCount = RTC_CounterGet();
+	RTC_Enable( false );
+
+	/* Enter a critical section but don't use the taskENTER_CRITICAL() method as
+	that will mask interrupts that should exit sleep mode. */
+	INT_Disable();
+	__asm volatile( "dsb" );
+	__asm volatile( "isb" );
+
+	/* The tick flag is set to false before sleeping.  If it is true when sleep
+	mode is exited then sleep mode was probably exited because the tick was
+	suppressed for the entire xExpectedIdleTime period. */
+	ulTickFlag = pdFALSE;
+
+	/* If a context switch is pending then abandon the low power entry as the
+	context switch might have been pended by an external interrupt that	requires
+	processing. */
+	eSleepAction = eTaskConfirmSleepModeStatus();
+	if( eSleepAction == eAbortSleep )
+	{
+		/* Restart tick and count up to whatever was left of the current time
+		slice. */
+		RTC_CompareSet( 0, ulReloadValueForOneTick - ulCurrentCount );
+		RTC_Enable( true );
+
+		/* Re-enable interrupts - see comments above the cpsid instruction()
+		above. */
+		INT_Enable();
+	}
+	else
+	{
+		/* Adjust the reload value to take into account that the current time
+		slice is already partially complete. */
+		ulReloadValue -= ulCurrentCount;
+		RTC_CompareSet( 0, ulReloadValue );
+
+		/* Restart the RTC. */
+		RTC_Enable( true );
+
+		/* Allow the application to define some pre-sleep processing. */
+		xModifiableIdleTime = xExpectedIdleTime;
+		configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
+
+		/* xExpectedIdleTime being set to 0 by configPRE_SLEEP_PROCESSING()
+		means the application defined code has already executed the WAIT
+		instruction. */
+		if( xModifiableIdleTime > 0 )
+		{
+			__asm volatile( "dsb" );
+			SLEEP_Sleep();
+			__asm volatile( "isb" );
+		}
+
+		/* Allow the application to define some post sleep processing. */
+		configPOST_SLEEP_PROCESSING( xModifiableIdleTime );
+
+		/* Stop RTC.  Again, the time the SysTick is stopped for is accounted
+		for as best it can be, but using the tickless mode will	inevitably
+		result in some tiny drift of the time maintained by the	kernel with
+		respect to calendar time.  The count value is latched before stopping
+		the timer as stopping the timer appears to clear the count. */
+		ulCurrentCount = RTC_CounterGet();
+		RTC_Enable( false );
+
+		/* Re-enable interrupts - see comments above the cpsid instruction()
+		above. */
+		INT_Enable();
+		__asm volatile( "dsb" );
+		__asm volatile( "isb" );
+
+		if( ulTickFlag != pdFALSE )
+		{
+			/* The tick interrupt has already executed, although because this
+			function is called with the scheduler suspended the actual tick
+			processing will not occur until after this function has exited.
+			Reset the reload value with whatever remains of this tick period. */
+			ulReloadValue = ulReloadValueForOneTick - ulCurrentCount;
+			RTC_CompareSet( 0, ulReloadValue );
+
+			/* The tick interrupt handler will already have pended the tick
+			processing in the kernel.  As the pending tick will be processed as
+			soon as this function exits, the tick value	maintained by the tick
+			is stepped forward by one less than the	time spent sleeping.  The
+			actual stepping of the tick appears later in this function. */
+			ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
+		}
+		else
+		{
+			/* Something other than the tick interrupt ended the sleep.  How
+			many complete tick periods passed while the processor was
+			sleeping? */
+			ulCompleteTickPeriods = ulCurrentCount / ulReloadValueForOneTick;
+
+			/* The reload value is set to whatever fraction of a single tick
+			period remains. */
+			ulReloadValue = ulCurrentCount - ( ulCompleteTickPeriods * ulReloadValueForOneTick );
+			if( ulReloadValue == 0 )
+			{
+				/* There is no fraction remaining. */
+				ulReloadValue = ulReloadValueForOneTick;
+				ulCompleteTickPeriods++;
+			}
+
+			RTC_CompareSet( 0, ulReloadValue );
+		}
+
+		/* Restart the RTC so it runs up to the alarm value.  The alarm value
+		will get set to the value required to generate exactly one tick period
+		the next time the RTC interrupt executes. */
+		RTC_Enable( true );
+
+		/* Wind the tick forward by the number of tick periods that the CPU
+		remained in a low power state. */
+		vTaskStepTick( ulCompleteTickPeriods );
+	}
+}
+/*-----------------------------------------------------------*/
+
+void RTC_IRQHandler( void )
+{
+	if( ulTickFlag == pdFALSE )
+	{
+		/* Set RTC interrupt to one RTOS tick period. */
+		RTC_Enable( false );
+		RTC_CompareSet( 0, ulReloadValueForOneTick );
+		ulTickFlag = pdTRUE;
+		RTC_Enable( true );
+	}
+
+	RTC_IntClear( _RTC_IFC_MASK );
+
+	/* Critical section which protect incrementing the tick*/
+	( void ) portSET_INTERRUPT_MASK_FROM_ISR();
+	{
+		if( xTaskIncrementTick() != pdFALSE )
+		{
+			/* Pend a context switch. */
+			portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
+		}
+	}
+	portCLEAR_INTERRUPT_MASK_FROM_ISR( 0 );
+}
+
+#endif /* ( configCREATE_LOW_POWER_DEMO == 1 ) */
+
diff --git a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/main_low_power.c b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/main_low_power.c
index fe4824d8c..ce30aa240 100644
--- a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/main_low_power.c
+++ b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/Low_Power_Demo/main_low_power.c
@@ -71,9 +71,10 @@
  * NOTE 1:  This project provides two demo applications.  A simple blinky demo
  * that demonstrates tickless low power operation, and a more comprehensive
  * test and demo application.  The configCREATE_LOW_POWER_DEMO setting in
- * FreeRTOSConfig.h is used to select between the two.  See the notes on using
- * configCREATE_LOW_POWER_DEMO in main.c.  This file implements the low power
- * version.
+ * FreeRTOSConfig.h is used to select between the two, and to select the clock
+ * used when tickless low power operation is demonstrated.  See the notes on
+ * using configCREATE_LOW_POWER_DEMO in main.c.  This file implements the low
+ * power version.
  *
  * NOTE 2:  This file only contains the source code that is specific to the
  * low power demo.  Generic functions, such FreeRTOS hook functions, and
@@ -211,7 +212,7 @@ const TickType_t xShortDelay = pdMS_TO_TICKS( 10 );
 		if( ulReceivedValue == ulExpectedValue )
 		{
 			/* Turn the LED on for a brief time only so it doens't distort the
-			enerty reading. */
+			energy reading. */
 			BSP_LedSet( mainTASK_LED );
 			vTaskDelay( xShortDelay );
 			BSP_LedClear( mainTASK_LED );
diff --git a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/main.c b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/main.c
index 174073296..fe76f5464 100644
--- a/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/main.c
+++ b/FreeRTOS/Demo/CORTEX_EFM32_Gecko_Starter_Kit_Simplicity_Studio/Source/main.c
@@ -71,10 +71,12 @@
  * This project provides two demo applications.  A simple blinky style project
  * that demonstrates low power tickless functionality, and a more comprehensive
  * test and demo application.  The configCREATE_LOW_POWER_DEMO setting, which is
- * defined in FreeRTOSConfig.h, is used to select between the two.  The simply
- * blinky low power demo is implemented and described in main_low_power.c.  The
- * more comprehensive test and demo application is implemented and described in
- * main_full.c.
+ * defined in FreeRTOSConfig.h, is used to select between the two, and to select
+ * the clock used when demonstrating tickless functionality.
+ *
+ * The simply blinky low power demo is implemented and described in
+ * main_low_power.c.  The more comprehensive test and demo application is
+ * implemented and described in main_full.c.
  *
  * This file implements the code that is not demo specific, including the
  * hardware setup and standard FreeRTOS hook functions.
@@ -85,6 +87,8 @@
  *
  */
 
+#warning Check the tick suppression routine in the case where the system unblocks before an entire tick period has expired.
+
 /* FreeRTOS includes. */
 #include "FreeRTOS.h"
 #include "task.h"
@@ -132,7 +136,7 @@ int main( void )
 
 	/* The mainCREATE_LOW_POWER_DEMO setting is described at the top
 	of this file. */
-	#if( configCREATE_LOW_POWER_DEMO == 1 )
+	#if( configCREATE_LOW_POWER_DEMO != 0 )
 	{
 		main_low_power();
 	}
@@ -154,6 +158,8 @@ static void prvSetupHardware( void )
 	BSP_TraceProfilerSetup();
 	SLEEP_Init( NULL, NULL );
 	BSP_LedsInit();
+
+	SLEEP_SleepBlockBegin( configENERGY_MODE );
 }
 /*-----------------------------------------------------------*/