nRF52840 BLE doesn't work but no errors

RE: nRF52840 BLE doesn't work but no errors

dmitry.kurochkin — Mon, 06 Jul 2020 08:48:34 GMT

We found the issue in 32 MHz crystal circuit. Now BLE is working.

Thank you.

RE: nRF52840 BLE doesn't work but no errors

hmolesworth — Fri, 03 Jul 2020 16:49:46 GMT

Maybe the 32kHz crystal has an issue, so worth trying not using the 32kHz crystal to test that possibility. Add something like this at the start of sdk_config.h:

// add "_NO_32_KHZ_CRYSTAL" to project preprocessor (or just comment out)
//#if defined(_NO_32_KHZ_CRYSTAL)
#define NRFX_CLOCK_CONFIG_LF_SRC         0
#define CLOCK_CONFIG_LF_SRC              0
#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 // <1=> NRF_CLOCK_LF_ACCURACY_500_PPM
//#endif

In bsp_init use this:

   APP_ERROR_CHECK(nrf_drv_clock_init());
   nrf_drv_clock_lfclk_request(NULL);

This works on my boards which don't have reliable 32kHz crystals

RE: nRF52840 BLE doesn't work but no errors

dmitry.kurochkin — Fri, 03 Jul 2020 16:27:00 GMT

Thanks for the reply

We changed the load caps that you suggest on 15 pF, but this does not work too.

The same antenna and circuit of clock works in our other project with nRF52832.

RE: nRF52840 BLE doesn't work but no errors

ketiljo — Wed, 01 Jul 2020 14:27:57 GMT

What's the CL value of the 32 MHz and the 32 kHz crystals you are using? You can calculate the values of the load caps:

Ccap = CL * 2 - Cpin, where Cpin = 4 pF. Round down to the nearest standard value. 12 pF load caps are good only for crystals with a CL value of 8 pF