High power consumption after disconnect

[Gordon]

Hi,

I've just hit a strange issue with SDK 12.1 on nRF52832.

Usually on BLE_GAP_EVT_DISCONNECTED, sd_ble_gap_adv_start gets called to start advertising and everything's great.

However, if I don't call sd_ble_gap_adv_start, advertising stops (as you'd expect) but the CPU seems to get left on - drawing 3-4mA of power!

Do you have any idea what could be causing this, and how to fix it?

Some of my users want to be able to disconnect and stop the device advertising so when used in HID mode the computer doesn't keep connecting. Then when a button is pressed it'll wake and get connected to. This all works fine, however the 'low power' mode ends up drawing 3mA!

[Sigurd]

Hi,

Is this with DC/DC mode enabled? What example in the SDK is your code based on ? Could be that the CPU is not entering sleep mode, or some interrupt is constantly waking the CPU up from sleep.

[Gordon]

Thanks! Yes, DC/DC is enabled. It seems to stay inside sd_app_evt_wait most of the time (the same as usual) so I'm pretty sure that's not it. The code is based on a whole mix of examples, so I can't track down one in particular. If it helps, it's all online (mainly in github.com/.../bluetooth.c).

I just tested with/without DC/DC and that's the problem it seems. Without it's fine, but when turned on the power usage jumps up when disconnecting and not starting advertising right after. Is there a way around this - Short of turning it off?

[Sigurd]

What revision of the nRF52832 are you using? If you are using an old revision, it could be this errata that is causing the issue. (Engineering B and older)

[Gordon]

Is there an address I can check to find out exactly which one? The devices that are hit are actually using Raytac MDBT42 modules - there are ~6000 of them out there so I'd hoped they wouldn't be engineering models. Having said that they definitely require the HAL_NFC_ENGINEERING_BC_FTPAN_WORKAROUND definition for NFC, so it looks like they are either B or C.

[Sigurd]

There is an overview here. Packet variant and build code can be read from markings on top of the nRF52 IC.

Alternatively, it could also be found be reading the FICR register.( NRF_FICR->INFO.VARIANT )