RE: Configuring BLE/Soft Device on Adafruit Feather nRF52840 Sense

Edvin — Mon, 07 Sep 2020 11:39:34 GMT

I suspect that the Adafruit Feather doesn't have an external LFXTAL. This is the most common pitfall when users tries to use "custom" PCBs.

Open sdk_config.h in your project and look for the following definitions, and set them accordingly:

#define NRF_SDH_CLOCK_LF_SRC 0
#define NRF_SDH_CLOCK_LF_RC_CTIV 16
#define NRF_SDH_CLOCK_LF_RC_TEMP_CTIV 2
#define NRF_SDH_CLOCK_LF_ACCURACY 1

I believe that this should solve your issue.

Some background:

The nRF has two options for the LFCLK. Either it can use an external LFXTAL, or the internal RC Oscillator. The nRF52840 DK has an external LFXTAL, so it is used by default in most examples. If the custom PCB doesn't have this external LFXTAL, and the project sets the LFCLK source to an external XTAL, the softdevice will try to start this XTAL, and wait for it to respond. If it doesn't respond, the softdevice will just stop in this wait state, which is probably what you are seeing.

Regarding the specific numbers that you should set in the sdk_config.h (pasted above), please see the description of the struct nrf_clock_lf_cfg_t in nrf_sdm.h.

Best regards,

Edvin

RE: Configuring BLE/Soft Device on Adafruit Feather nRF52840 Sense

Gordon Wallace — Fri, 04 Sep 2020 19:04:44 GMT

Thanks for your reply - I did flash the SoftDevice.

RE: Configuring BLE/Soft Device on Adafruit Feather nRF52840 Sense

Patrick — Fri, 04 Sep 2020 17:31:13 GMT

Did you flash the SoftDevice in addition to the firmware?