how to reduce the power consumption in ble_app_uart?

[siltvm]

We've started development on a project using ble_app_uart as its base. We're using the nRF52832, Segger Embedded Studio (version 5.42a), and nRF5 SDK version 17.0.2. Minimizing power consumption is a critical factor for us; currently, the board's average current consumption is 25mA during the advertisement state. Can you suggest methods to reduce power consumption in the ble_app_uart example code? We don't need to use UART, so are there ways to remove it from the code and, in doing so, reduce power consumption?

controller :- nrf52832 

ide :- seggar embedded studio (5.42a) 

sdk :- nrf5sdk 17.0.2 

[Parth Parekh]

Power Optimization Steps

1. Remove UART (app_uart / UART driver)

The ble_app_uart example initializes and runs UART continuously via the app_uart module. This keeps the UART peripheral active and contributes to a constant power drain.

Actions:

• Remove the call to app_uart_init(...) in main.c.

• Delete or comment out:

  #include "app_uart.h"
  #include "nrf_uart.h"
  

• Remove the uart_event_handle(...) function and related logic.

• If you’re not using logs over RTT or UART, also disable NRF_LOG.

2. Disable Unused Peripherals

Peripherals like SPI, TWI, ADC, etc., if initialized but not used, can increase power consumption.

Checklist:

• Review all nrf_drv_*_init() and nrfx_*_init() calls.

• Open sdk_config.h and disable unused modules by setting:

  #define UART_ENABLED 0
  #define APP_UART_ENABLED 0
  #define NRF_LOG_ENABLED 0
  #define NRFX_UART_ENABLED 0
  #define NRFX_UARTE_ENABLED 0
  #define BSP_BTN_BLE_ENABLED 0
  

3. Optimize Advertising Interval

Adjust the advertising interval to a larger value for lower power. In main.c:

#define APP_ADV_INTERVAL 1600  // 1000 ms = 1600 * 0.625 ms

Pass this value to the advertising module using ble_advertising_init().

Nordic recommends 1000–2000 ms for ultra-low-power advertising.

4. Ensure Sleep Mode is Entered Properly

Between BLE events, the CPU should enter sleep (WFE).

Your main loop should look like:

while (true)
{
    idle_state_handle();
}

And idle_state_handle() should call:

void idle_state_handle(void)
{
    if (NRF_LOG_PROCESS() == false)
    {
        nrf_pwr_mgmt_run(); // internally calls __WFE()
    }
}

Confirm nrf_pwr_mgmt_init() is called during initialization.

5. Enable the On-Chip DC-DC Regulator

If your hardware has the required external components (inductor), enable the DC/DC converter:

NRF_POWER->DCDCEN = 1;

To change output voltage, modify the UICR register (run once):

NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen;
while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
NRF_UICR->REGOUT0 = (UICR_REGOUT0_VOUT_1V8 << UICR_REGOUT0_VOUT_Pos);
NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren;
while (NRF_NVMC->READY == NVMC_READY_READY_Busy);
NVIC_SystemReset(); // Reset to apply changes

6. Verify LFCLK Configuration

Ensure that nrf_drv_clock_init() is called before using SoftDevice or nrf_pwr_mgmt_run().

The 32.768 kHz LFCLK is essential for BLE and accurate RTC timing while sleeping.

Expected Power Consumption (nRF52832 + SoftDevice S132)

Configuration	Avg. Current Draw
UART + Logs + 100ms Adv Interval	1–10 mA
UART removed + 1s Adv Interval	20–50 µA
Sleep mode (no advertising)	2–3 µA

Conclusion

With UART disabled, peripherals shut down, advertising optimized, and proper sleep configuration, the power consumption of the ble_app_uart example can be brought down from ~25 mA to under 50 µA.