High power consumption of softdevice

Question

Hello! 
 I am working on firmware for device that has freertos in the base and implements BLE beacon and 1 service with 7 characteristics. Everything works. But power consumption is too high. 
 After plenty of tests on final HW, I've created playground based on ble_app_hrs_freertos_pca10040_s132 sample project and switched to sparkfun board. 
 When have just FreeRTOS with no user-defined tasks, consumption is about 1uA. 
 After I call ble_stack_init with code below, I got about 500uA. It is without advertising at all. 
 static void ble_stack_init(void)
{
 ret_code_t err_code;

 err_code = nrf_sdh_enable_request();
 APP_ERROR_CHECK(err_code);

 // Configure the BLE stack using the default settings.
 // Fetch the start address of the application RAM.
 uint32_t ram_start = 0;
 err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
 APP_ERROR_CHECK(err_code);

 // Enable BLE stack.
 err_code = nrf_sdh_ble_enable(&ram_start);
 APP_ERROR_CHECK(err_code);

 // Register a handler for BLE events.
 NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
} 
 When beacon is enabled I have cca 650uA. 
 When GATT and beacon are working I have cca 750uA. 
 I measure with multimeter. 
 Results seems fine for me except for those 500uA after stack is initialized. Why is it so high? What can I do to lower it? 
 
 SDK v 15.0 
 NRF_LOG_ENABLED is 0 
 Using RELEASE configuration. 
 Tried S132 and S140 - result is the same

Elias Löwe · Accepted Answer

Hi David!

I can confirm, that Aryan's answer worked for me. I just changed #if 0 to #if 1

# file port_cmsis_systick.c

#if 1  // With FreeRTOS sd_app_evt_wait increases power consumption with FreeRTOS compared to _WFE (NRFFOSDK-11174)
#ifdef SOFTDEVICE_PRESENT
            if (nrf_sdh_is_enabled())
            {
                uint32_t err_code = sd_app_evt_wait();
                APP_ERROR_CHECK(err_code);
            }
            else
#endif
#endif // (NRFFOSDK-11174)

This did its job for demo project.

Also for this project I had to do few more things:

1. As far as I used floating point calculations, I had to chnage my main.c module as follows:

int main(void)
{
    NVIC_SetPriority(FPU_IRQn, APP_IRQ_PRIORITY_LOW);
    NVIC_EnableIRQ(FPU_IRQn);

    /* application code */
    ...
}

#define FPU_EXCEPTION_MASK 0x0000009F

void FPU_IRQHandler(void)
{
    uint32_t *fpscr = (uint32_t *)(FPU->FPCAR+0x40);
    (void)__get_FPSCR();

    *fpscr = *fpscr & ~(FPU_EXCEPTION_MASK);
}

2. We use SAADC module for some measurements and I had to uninitialise it after usage like this after each usage:

nrf_drv_saadc_uninit();
   
NRF_SAADC->INTENCLR = (SAADC_INTENCLR_END_Clear << SAADC_INTENCLR_END_Pos);

NVIC_ClearPendingIRQ(SAADC_IRQn);

And now average power consumption is about 30uA.

p.S. Sorry for late answer, so much work here...

Susheel Nuguru · Answer

I think i found the problem. 
 It is in port_cmsis_systick.c 
 #if 0 // With FreeRTOS sd_app_evt_wait increases power consumption with FreeRTOS compared to _WFE (NRFFOSDK-11174)
#ifdef SOFTDEVICE_PRESENT
 if (nrf_sdh_is_enabled())
 {
 uint32_t err_code = sd_app_evt_wait();
 APP_ERROR_CHECK(err_code);
 }
 else
#endif
#endif // (NRFFOSDK-11174) 
 I do not remember the exact way i came to a conclusion that sd_app_evt_wait was consuming more power with freertos. Hence I created an internal ticket NRFFOSDK-11174 to investigate why this happened. I remembered that i was reading more power with freertos and using sd_wait function. While using WFI it was less. This technically did not make sense, but i decided to comment out sd_app_evt_wait function until i get more results. But I am not able to reproduce this anymore. So i think this comment is the problem on SDK 15. 
 Please change line 231 in port_cmsis_systick.c to below 
 #ifdef SOFTDEVICE_PRESENT
 if (nrf_sdh_is_enabled())
 {
 uint32_t err_code = sd_app_evt_wait();
 APP_ERROR_CHECK(err_code);
 }
 else
#endif
 
 I will try to push these changes to official SDK for the next release.

Elias Löwe · Answer

Hi Rahmat, 
 yes, make sure that UART and logging is switched off in your sdk_config.h and that you are not running your application with debugger. 
 Maybe some more information about your application could help to point you. 
 
 Cheers, 
 Elias

High power consumption of softdevice

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