nRF52840 custom board does not advertise

RE: nRF52840 custom board does not advertise

Vidar Berg — Mon, 28 Dec 2020 09:00:48 GMT

Thanks for the update! So it is not working with NRF_CLOCK_LF_SRC_SYNTH? NRF_CLOCK_LF_SRC_SYNTH relies on the HFXO (32MHz crystal) so maybe the HF crystal is not starting at all.

Could you try to see if you are able to start the HFXO at the beginning of main() as shown in the snippet below?

    NRF_CLOCK->TASKS_HFCLKSTART = 1;
    /* Wait until the crystal oscillator has started */
    while(NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)
      {};

You may also try the RSSI Viewer app in nRF connect for desktop to check if the RADIO is transmitting anything if you have a nordic dev kit or dongle laying around.

RE: nRF52840 custom board does not advertise

ddjsbx — Thu, 24 Dec 2020 15:58:03 GMT

Ignore this! I had experimented with different LF clock source settings in sdk_config.h, trying to diagnose why one board would not return from sd_softdevice_enable().. That particular board did have a dead LF crystal, and I got it to return from sd_softdevice_enable by changing NRF_SDH_CLOCK_LF_SRC to NRF_CLOCK_LF_SRC_SYNTH. But I had left sdk_config,h modfied and apparently that prevents sd_softdevice_enable if the LF crystal oscillator is working.

I have another interesting data point. I am pretty sure that at one point I had this board advertising successfully using ble_app_blinky modified to work with my board. But last time I tried it that did not advertise either. I decided to try another example, app_beacon. I modified that example to work with my board, and app_beacon does advertise. This is starting to seem like some kind of random startup issue. Does the nRF52840 start up with RC oscillator then switch to xtal? What if the xtal sometimes did not start, so it remained running from RC. Could that show up as not advertising? (Opposed to this scenario, one of my hardware guys examined both LF and HF oscillators on a board that doesn't advertise, and they both seemed to be running fine)

RE: nRF52840 custom board does not advertise

ddjsbx — Wed, 23 Dec 2020 15:13:43 GMT

Hi Vidar, that's an interesting possibility, we will look into it. Do you think that if the start advertising call returns success, that means that down in the softdevice it should be busily sending advertisement packets, but that it really has no way of knowing if the radio is working or if the packets are actually going out over the air? Do you know if there is a case where SD replies success and starts advertising but then gets somehow bumped out of its "advertising" state? Would registering for "radio events" tell us if something like this happens? (I saw some reference to registering for radio events, I don't think our firmware currently has that)

RE: nRF52840 custom board does not advertise

Vidar Berg — Wed, 23 Dec 2020 14:56:53 GMT

Hello,

Could it maybe be related to the 32M crystal as one user reported here: https://devzone.nordicsemi.com/f/nordic-q-a/66107/samsung-a-series-not-detecting-nrf52832? The Softdevice has no way of knowing if the HF clock is accurate or not.

Best regards,

Vidar