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Low Power LLS Mode on Freescale's Kinetis FRDM-KL25Z board

This tutorial was extracted from Erich Styger blog http://mcuoneclipse.wordpress.com with his agreement.


In “IoT: FreeRTOS Down to the Micro Amps” I’m using an application with FreeRTOS to get down in micro amps low power mode. Well, nearly all or my applications are using FreeRTOS because it makes the application scalable and extensible. Still, for anyone not used to an RTOS, that might be a hard start. So here we go: how to get into the Kinetis Low Power LLS Mode *without* an RTOS.


                         Power Measurement

                                                                 Power Measurement


Outline

In this project I create a very simple bare-metal application for the Freescale FRDM-KL25Z board. All what it does is to blink an LED from the Low Power wake-up interrupt to show that the application is running. Right after the wake-up interrupt, it enters again the LLS low power mode. So I enter LLS low power mode, and the timer interrupt will wake me up every second. As in LLS mode only a few timer and wake-up sources are available, I’m going to use the 1 kHz Low Power clock source.

The project and all the settings is available on GitHub at the link provided at the end of this article.

Processor Expert Components

In this project, I’m using the following components:

  1. 3 LED components (RGB)
  2. TimerInt with TimerUnit_LDD for the low power wake-up timer
  3. WAIT component to flash different LED’s after power-up with a delay.

                         Processor Expert Components

                                   Processor Expert Components

Timer

As timer I use the LPTMR with a period of one second:

                         Low Power 1 Second Timer

                                                            Low Power 1 Second Timer

Inside the period settings, I configure it to use the LPO 1 kHz timer as clock source, as this clock still will run in LLS mode:

                         LPO 1 kHz Source

                                                            LPO 1 kHz Source

CPU Component

First, we need to configure the CPU component to be ready for low power mode. I enable the methods SetOperationMode() and GetLLSWakupFlags() (so the black x is removed):

                         Enabled SetOperationMode and GetLLSWakeupFlags

                                        Enabled SetOperationMode and GetLLSWakeupFlags

In the CPU properties, I enable all low power modes, configure LPTMR0 as wake-up source, and enable the INT_LLW wake-up interrupt:

                         Enabled Low Power Modes

                                                           Enabled Low Power Modes

Then I configure the WAIT, SLEEP and STOP modes (these are the three different low power modes in Processor Expert):

                         WAIT, SLEEP and STOP modes

                                                  WAIT, SLEEP and STOP modes

Source Files

Time to write the application code. I’m using Application.h and Application.c:

 

/*

* Application.h

*

*  Created on: Mar 16, 2014

*      Author: Erich Styger

*/

#ifndef APPLICATION_H_

#define APPLICATION_H_

/*! \brief callback called from the LLS wake-up interrupt */

voidAPP_OnLLSWakeUpInterrupt(void);

/*! \brief callback called from low power timer interrupt */

voidAPP_TimerInterrupt(void);

/*! \brief application main entry point */

voidAPP_Run(void);

#endif /* APPLICATION_H_ */

 

The the Application.c looks like this:

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/*

 

* Application.c

*

*  Created on: Mar 16, 2014

*      Author: Erich Styger

*/

 

#include "Application.h"

#include "LED1.h"

#include "LED2.h"

#include "LED3.h"

#include "WAIT1.h"

#include "LPTMR_PDD.h"

 

void APP_OnLLSWakeUpInterrupt(void) {

  uint32_t tmp;

 

  tmp = Cpu_GetLLSWakeUpFlags();

  if (tmp&LLWU_INT_MODULE0) { /* LPTMR */

    LPTMR_PDD_ClearInterruptFlag(LPTMR0_BASE_PTR); /* Clear interrupt flag */

  }

}

 

void APP_TimerInterrupt(void) {

  LED1_Neg(); /* red LED */

}

 

void APP_Run(void) {

  LED2_On();

  WAIT1_Waitms(1000);

  LED2_Off();

  for(;;) {

    //LED3_Neg(); /* blue LED */

    //Cpu_SetOperationMode(DOM_WAIT, NULL, NULL); /* next interrupt will wake us up */

    //Cpu_SetOperationMode(DOM_SLEEP, NULL, NULL); /* next interrupt will wake us up */

    Cpu_SetOperationMode(DOM_STOP, NULL, NULL); /* next interrupt will wake us up */

  }

}

From main() in ProcessorExpert.c I call APP_Run():

 

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#include "PE_Types.h"

 

#include "PE_Error.h"

#include "PE_Const.h"

#include "IO_Map.h"

 

/* User includes (#include below this line is not maintained by Processor Expert) */

#include "Application.h"

 

/*lint -save  -e970 Disable MISRA rule (6.3) checking. */

int main(void)

/*lint -restore Enable MISRA rule (6.3) checking. */

{

  /* Write your local variable definition here */

 

  /*** Processor Expert internal initialization. DON'T REMOVE THIS CODE!!! ***/

  PE_low_level_init();

  /*** End of Processor Expert internal initialization.                    ***/

 

  APP_Run();

 

  /*** Don't write any code pass this line, or it will be deleted during code generation. ***/

  /*** RTOS startup code. Macro PEX_RTOS_START is defined by the RTOS component. DON'T MODIFY THIS CODE!!! ***/

  #ifdef PEX_RTOS_START

    PEX_RTOS_START();                  /* Startup of the selected RTOS. Macro is defined by the RTOS component. */

  #endif

  /*** End of RTOS startup code.  ***/

  /*** Processor Expert end of main routine. DON'T MODIFY THIS CODE!!! ***/

  for(;;){}

  /*** Processor Expert end of main routine. DON'T WRITE CODE BELOW!!! ***/

} /*** End of main routine. DO NOT MODIFY THIS TEXT!!! ***/

And from Events.c I call my hooks:

 

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/*

 

** ===================================================================

**     Event       :  TI1_OnInterrupt (module Events)

**

**     Component   :  TI1 [TimerInt]

**     Description :

**         When a timer interrupt occurs this event is called (only

**         when the component is enabled -  and the events are

**         enabled - ). This event is enabled only if a

**          is enabled.

**     Parameters  : None

**     Returns     : Nothing

** ===================================================================

*/

void TI1_OnInterrupt(void)

{

  APP_TimerInterrupt();

}

 

/*

** ===================================================================

**     Event       :  Cpu_OnLLSWakeUpINT (module Events)

**

**     Component   :  Cpu [MKL25Z128LK4]

*/

/*!

**     @brief

**         This event is called when Low Leakage WakeUp interrupt

**         occurs. LLWU flags indicating source of the wakeup can be

**         obtained by calling the [GetLLSWakeUpFlags] method. Flags

**         indicating the external pin wakeup source are automatically

**         cleared after this event is executed. It is responsibility

**         of user to clear flags corresponding to internal modules.

**         This event is automatically enabled when [LLWU interrupt

**         request] is enabled.

*/

/* ===================================================================*/

void Cpu_OnLLSWakeUpINT(void)

{

  APP_OnLLSWakeUpInterrupt();

}

Summary

This application shows how to set up an application for Low Power LLS mode, in a bare-metal mode. So it should be useful for you if you want to have a starting point for your own project without an RTOS.

The project and sources are available on GitHub.