Problem with BLE Low Power Mode

[john_h]

Hello,

I am using nRF52832 and having a problem with the Low Power Mode. I am not sure if I am either not getting it to stay in low power mode when my UART is initialized, or if low power mode is using too much power.

When I do not even initialize the UART, my low power mode sees current usage in the 100s μA range

When I initialize my UART and then almost immediately uninitialize it, my sleep mode has a current draw of about 5-6mA. I have also disabled easy DMA to try to get the UART to use less power. Any ideas as to what is going on here? I have no other timers and am not connecting to it, so there should be no other events that wake it from this mode.

const app_uart_comm_params_t comm_params
    = { RX, TX, 0, 0, APP_UART_FLOW_CONTROL_DISABLED, false, UART_BAUDRATE_BAUDRATE_Baud115200 };
    
  uint32_t                     err_code;
  APP_UART_FIFO_INIT(&comm_params, UART_RX_BUF_SIZE, UART_TX_BUF_SIZE, uart_event_handle, APP_IRQ_PRIORITY_LOW,
                     err_code);
  error_code_check(err_code);
  APP_ERROR_CHECK(err_code);
  nrf_gpio_cfg(TX, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_DISCONNECT, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_H0D1,
               NRF_GPIO_PIN_NOSENSE);
  nrf_gpio_cfg(RX, NRF_GPIO_PIN_DIR_INPUT, NRF_GPIO_PIN_INPUT_DISCONNECT, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_H0D1,
               NRF_GPIO_PIN_NOSENSE);
               
//configure UART signal interrupt
  err_code = nrf_drv_gpiote_init();
  APP_ERROR_CHECK(err_code);

  nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_LOTOHI(true);
  in_config.pull = NRF_GPIO_PIN_PULLDOWN;
  APP_ERROR_CHECK(err_code);

  err_code = nrf_drv_gpiote_in_init(UART_ALERT, &in_config, uart_alert_handler);
  APP_ERROR_CHECK(err_code);

  nrf_drv_gpiote_in_event_enable(UART_ALERT, true);


while(true) {
    nrf_drv_uart_rx_disable(&app_uart_inst);
    app_uart_close();
    nrf_drv_gpiote_in_event_disable(UART_ALERT);
    nrf_drv_gpiote_in_uninit(UART_ALERT);
    NRF_UART0->EVENTS_RXDRDY = 0;

    //need this delay to let it go to sleep
    nrf_delay_ms(1000);
    //NVIC_ClearPendingIRQ(UART1_IRQn);
    //NVIC_ClearPendingIRQ(GPIO_ODD_IRQn);
    sd_app_evt_wait();

}

I have confirmed that the GPIOTE is not the issue in a separate isolated test. It seems to be something with the UART either causing a much higher current draw or not allowing the board to remain asleep

[Susheel Nuguru]

seems like the uart uninit function is leaving something enabled. I would have to reproduce this tomorrow, which SDK version did you use? Is the code snippet you attached, enough for me to be able to reproduce this issue?

[john_h]

I think should be enough. I also have events for ble connections but shouldn't be an issue. I am using version 12.3 with s130

All my uart init/uninit is in uart library app_uart_fifo.c which is very similar to app_uart.c. I moved some of the code out of there and into this snippet just to make it more clear.

[Susheel Nuguru]

If this is all I need, then i will test this tomorrow morning as its pretty late here in Norway

[john_h]

As a note... I was able to get it into the lowest power mode when I switched to the non-FIFO uart. Is there any reason for this?

[Susheel Nuguru]

It looks like in your code snippet, you are trying to uninitialize the UART before you are calling app_uart_init.

Please check in a debugger to see if when using app_fifo and when calling nrf_drv_uart_rx_disable/app_uart_close fails with a return code and is stuck in the app_error handler?