Could I move the external 32.768kHz crystal on 51822 for keyboard application???

[jimlin]

Hi,

As the title said, I need more GPIOs for application, and could I use the XL1 and XL2 ?
What happen when use RC oscillator instead?

Thanks.

[FormerMember]

You'll have to add the current required for the HF_CLK. The datasheet says that HF_CLK oscillator will consume around 470uA when it needs to drive for any peripheral, 25 uA if it is idle. I guess (not sure) HF_CLK providing clock to LF_CLK accounts to it being active, so 470 uA more, which is quite a bit. I hope someone can clarify this.

[syntroniks]

In my experiments running with LFCLKSRC_RC_OSC_4000 I notice a few microamps higher current consumption relative to the 32khz crystal. Perhaps the hf clock is turned off inbetween connection events. The 16MHz osc is not a requirement of the internal 32khz osc. The synthesized lf clock, however, does require the HFCLK to be running. I don't know why there is even a synthesized clock :D Limited uses I guess

[FormerMember]

Yeah, couldn't come up with a realistic low power use case where the synthesized clock would be useful.