5 Replies Latest reply on Jun 4, 2018 11:32 PM by hiyoc_2758731

    HIB_XTAL is not used



      We are developing the application board using CYW43907 (Murata LBWA1UZ1GC module) now.

      We don't want to use external 32.768kHz crystal to HIB_XTAL_IN/OUT.

      HIB_LPO_SEL must be pulled high in this case.

      How can we terminate HIB_XTAL_IN and HIB_XTAL_OUT ?

      Is it OK to leave them open ?



        • 1. Re: HIB_XTAL is not used

          Moving to the Murata community, adding ToIn_1742091

          • 2. Re: HIB_XTAL is not used

            Pull's and traps for HIB LPO sel should not affect, since these are anyway override by SW. HIB_LPO_SEL pin is supposed to *guarantee* which source you’re getting for the 32kHz clock. By default it’s auto selected between the external xtal and the internal oscillator. If you have only the internal oscillator then HIB_LPO_SEL is useless. Also this pull is over ride by SW when making LPO source definitions in platform.c.


            The thing what matter is wrong configuration of LPO source in platform.c- if you have XTAL populated the device wont boot-up if platform.c have defined using iLPO. This works also vice-versa. Bellow definition in platform.c to configure the LPO either using internal RC-osc or external XTAL


            Internal RC oscillator = PLATFORM_HIBERNATION_CLOCK_INTERNAL_32KHZ



            const platform_hibernation_t hibernation_config = {

                .clock              = PLATFORM_HIBERNATION_CLOCK_INTERNAL_32KHZ,

                .hib_ext_clock_freq = 0, /* use default settings */

                .rc_code            = PLATFORM_HIB_WAKE_CTRL_REG_RCCODE,


            1 of 1 people found this helpful
            • 3. Re: HIB_XTAL is not used

              Hi jaka san,


              Thank you for very helpful information.

              When we define iLPO in the software, can we leave HIB_XTAL_IN/OUT as open ?



              • 4. Re: HIB_XTAL is not used



                Yes, after the 32k XTAL is remove the pins can be left floating/open. Although for first proto I would recommend you have at least landing pattern for the 32k XTAL and Pull UP resistor landing pattern for HIB_LPO_SEL. This is for the reason you can optimize component count by take components away one-by-one in controlled way, meanwhile verify the functionality.


                I have seen 32k XTAL removal done parallel with too many other changes then cannot tell which change affected to the end result.




                • 5. Re: HIB_XTAL is not used

                  Hi jarkko san,


                  We succeeded to boot up by defining iLPO in the software as your wrote.

                  Our board have the landing pattern of crystal to HIB_XTAL_IN/OUT but both

                  HIB_XTAL_IN/OUT are open now.


                  Thank you for your answers and helps.