Powering up after a sd_power_system_off().

[Sietse]

Hello List,

I have an Arduino Nano 33 ble with nrf52840.
It is powered directly with 3.3 Volt using 7 Volt and a 3.3 Volt LDO voltage regulator.
It is programmed (via the bootloader) using nRF5_SDK_17.1.0_ddde560 software.
The program is basically an adapted version of examples/ble_periphiral/ble_app_uart.

At some point I want to turn the system off by using a command send to it via BLE.
Then sd_power_system_off() is called.
After turning power off (switch between 7 Volt and LDO) and then it on again, the system should boot and advertise itself, but it doesn't.
Only after using the reset button (RESETN of the NINA-B3X) on the Nano does it start properly.

Is the power cycle not seen as a proper reset?
How can I make it start properly in this scenario?
Thanks again, Sietse

[Priyanka]

Hi,

This can occur due to several reasons. Please check the following:

1. Please make sure that the brownout detector of the nRF52840 is configured correctly in your application. If it doesn't detect the power-off state properly, this can occur.

2. Also, ensure that there is enough time between powering on and off the circuit.

3. You can try to use a GPIO pin to manually control the reset pin of the nRF52840. This can be done by connecting a GPIO pin to the RESETN pin and toggling it low in your application, before system off. 

4. You can also try to use an external reset circuit, say, a simple RC circuit, so that when power is applied, the proper reset signal is sent to RESETN pin.

Please try these and let me know how it goes.

Regards,

Priyanka