Can I run ble_app_hrs sample using internal rc clock only?

RE: Can I run ble_app_hrs sample using internal rc clock only?

Marc Nicholas — Wed, 23 Oct 2013 02:38:46 GMT

Correct. Bluetooth (not just Low Energy) needs a fairly tight PPM on the clock source (40ppm) and you just won't get that with an RC.

-m

RE: Can I run ble_app_hrs sample using internal rc clock only?

Bastiaan — Tue, 22 Oct 2013 16:49:09 GMT

did not get an ERR_CODE, instead ble_stack_handler_init hangs.

RE: Can I run ble_app_hrs sample using internal rc clock only?

Guest — Tue, 22 Oct 2013 16:49:09 GMT

did not get an ERR_CODE, instead ble_stack_handler_init hangs.

RE: Can I run ble_app_hrs sample using internal rc clock only?

Chris — Tue, 22 Oct 2013 16:47:10 GMT

Ok thanks, you have confirmed that I need external crystal. Once I added that everything works great. I'm running your heart rate profile sample code and it is working perfectly.

I would love to know the reason. I assume the 16MHz crystal gives better accuracy needed for BLE to work?

RE: Can I run ble_app_hrs sample using internal rc clock only?

Hung Bui — Tue, 22 Oct 2013 10:23:44 GMT

Hi,

Have you make sure you have the a 16 MHz external crystal ?

The BLE stack requires both 16 MHz and 32 kHz oscillator. The 16 MHz clock source must be provided from external crystal because it's for radio operation as you already quoted. The 32 kHZ clock source can be from external crystal or internal RC with the only requirement of having tolerance lower than 250ppm.

You should have no problem using NRF_CLOCK_LFCLKSRC_RC_250_PPM_4000MS_CALIBRATION as LFCLK.

Do you receive an ERR_CODE after the call to ble_stack_handler_init() ?