RE: ble connection trace after power down

Jørgen Holmefjord — Wed, 03 Jan 2024 12:44:29 GMT

Hi,

There is no register keeping information about BLE connection status. BLE protocol state is known only to the software stack, the RADIO peripheral just sends/receives packets defined by the SW.

You can use the Power supply supervisor to get an early warning when battery voltage becomes too low, but unfortunately, it is not possible to write the connection state to flash directly if you get into this state: "If power-fail warning is enabled and the supply voltage is below V_POF the power-fail comparator will prevent the NVMC from performing write operations to the NVM."

Depending on the voltage level where the warning is generated, you could disable the Power supply supervisor feature (or perform a soft reset with GPREGRET register set to a specific value that is written to flash on boot) to write the state to flash before the device is powered down.

Another alternative is to always write the connection state to flash, for instance using NVS library, but this could wear out flash over time if you have lots of connect/disconnects (flash is rated for 10000 write/erase cycles per page).

Best regards,
Jørgen