LED2 slowly blinking when Bootloader + SD are programmed to empty DK

[Nicolas Felipe]

I am working with nrf52840DK, SDK v17.1.0.

I compiled and downloaded the open bootloader project to the DK using SES (No errors and verification says OK). According to the documentation if the board does not have a valid application it should go to DFU mode, turning the LED3 on. But, the board is not advertising as far as I can tell, and the LED2 is slowly blinking. The other LED that is on is LED5.

I also tried programming the SD and BL using nrf connect. Same results.

I would appreciate if someone has an idea on what is happening, I can't find documentation on why LED2 might be blinking like that. 

Thank you so much, I hope I was clear enough.

[Amanda Hsieh]

Hi, 

The open bootloader example (examples/dfu/open_bootloader) is provided only with USB CDC ACM DFU Transport. See Open Bootloader with DFU documentation. 

If you look into the code, the LED2 means NRF_DFU_EVT_DFU_INITIALIZED:

        case NRF_DFU_EVT_DFU_INITIALIZED:
        {
            bsp_board_init(BSP_INIT_LEDS);

            if (!nrf_clock_lf_is_running())
            {
                nrf_clock_task_trigger(NRF_CLOCK_TASK_LFCLKSTART);
            }
            err_code = app_timer_init();
            APP_ERROR_CHECK(err_code);

            led_sb_init_params_t led_sb_init_param = LED_SB_INIT_DEFAULT_PARAMS(BSP_LED_1_MASK);

            uint32_t ticks = APP_TIMER_TICKS(DFU_LED_CONFIG_TRANSPORT_INACTIVE_BREATH_MS);
            led_sb_init_param.p_leds_port    = BSP_LED_1_PORT;
            led_sb_init_param.on_time_ticks  = ticks;
            led_sb_init_param.off_time_ticks = ticks;
            led_sb_init_param.duty_cycle_max = 255;

            err_code = led_softblink_init(&led_sb_init_param);
            APP_ERROR_CHECK(err_code);

            err_code = led_softblink_start(BSP_LED_1_MASK);
            APP_ERROR_CHECK(err_code);
            break;

Regards,
Amanda