How to use _WFI and WFE to enter idle mode

[Jorgewu]

Hi all: To saving power I implement the function to read data after interrupt is triggered..

below are my codes.. My expectation is..

Let CPU enter idle mode to wait interrupt by call _WFI() After interrupt is triggered start to read data and call _WFE() to save power. After read out 100 datas, CPU enter idle mode to wait interrupt triggered again...

However, the function of LIS3DH_ReadOutZYX(XYZ_Data) is always called even there is no any interrupt is triggered. How can I revise my code to meet my requirements? Thanks..

int main(void)
{
  BSP_Init();

  static bool bPoweSaving = true;


    int16_t         XYZ_Data[3]={0};

    uint8_t reg = 0;
    ret_code_t err_code;
    static int i = 0;

     
    while(true)
    {
     
        /* Start transaction with a slave with the specified address. */
     if( bPoweSaving)
     {
       __WFI();
       
     }
     else
     {
     
       __WFE();
     }
     bPoweSaving = false;
     err_code = LIS3DH_ReadOutZYX(XYZ_Data);  
    }
     i ++; 
     if (i > 100)
       bPoweSaving = true;
 
}

[Susheel Nuguru]

You still have a race condition when you use bPoweSaving with __WFI. Please read Anders comment here Because you are using WFI and the flag in the same context, I think it is ok but i see something wrong in you code.

I also do not understand your while state, since it will not allow the bPoweSaving to be set to true ever as while loop will never end

int main(void)
{
  BSP_Init();

  static bool bPoweSaving = false;


    int16_t         XYZ_Data[3]={0};

    uint8_t reg = 0;
    ret_code_t err_code;
    static int i = 0;


    while(true)
    {

        /* Start transaction with a slave with the specified address. */
     if( bPoweSaving)
     {
       bPoweSaving = false;
       __WFI();

     }
     else
     {
       __WFE();
     }

     err_code = LIS3DH_ReadOutZYX(XYZ_Data);  
     
     if (i++ > 100)
     {
       i = 0;  
       bPoweSaving = true;
     }
    }

}

This above code will first sleep on WFI on every 100th reads and sleeps on WFE before 0 to 99 reads.