Which clock is used for timing after BLE establishes a connection?

[ethan]

Hi,

I am analyzing the issue that the BLE module can maintain a relatively short connection distance. Besides the transmission power and frequency offset, I also take into account the factor of the clock, because the connection is a synchronous event and must have a certain relationship with the clock. 

I would like to ask, in the connection event, what type of clock is used to determine the next connection time? Is it a hardware TIMER or a software RTC? In other words, is it related to a high-frequency clock or a low-frequency clock?

[ethan]

Hi Susheel Nuguru,

Do you agree with Emil Lenngren's statement? That is, the LFCLK accuracy will not affect the connection distance but only increase power consumption.

[Susheel Nuguru]

No, the details of accuracy of the clock is given to the softdevice at the time of softdevice init using nrf_clock_lf_cfg_t . Please check nrf_sdh_enable_request and all the defines below that are defined in sdk_config.h file

    nrf_clock_lf_cfg_t const clock_lf_cfg =
    {
        .source        = NRF_SDH_CLOCK_LF_SRC,
        .rc_ctiv       = NRF_SDH_CLOCK_LF_RC_CTIV,
        .rc_temp_ctiv  = NRF_SDH_CLOCK_LF_RC_TEMP_CTIV,
    #if defined(S140) && (NRF_SD_BLE_API_VERSION < 6)
        .xtal_accuracy = NRF_SDH_CLOCK_LF_XTAL_ACCURACY
    #else
        .accuracy      = NRF_SDH_CLOCK_LF_XTAL_ACCURACY
    #endif
    };