is RTC necessary for RK3288 / linux kernel?

bschiett · Posted at 10/30/2016 04:28:21

Hi All
Is the RTC circuit in firefly rk3288 reload board necessary? I am designing my own board using the reload core module and don't need accurate date or time. I also will not use the ethernet PHY or wifi / BT chips. Does the RK3288 need the RTC, or does the kernel need to RTC?
Thanks
B

isle · Posted at 10/31/2016 09:58:13

Hi bschiett
in the core module ,the 3288 need a 32k clock which is supplied by RTC QQ截图20161031094406.png

whithout this ,the rk3288 have no the temparature protection.
and the other thing ,when go to sleep ,the rk3288 change it's clock from 24M to this 32K.
so we suggest you to hold it .

bschiett · Posted at 11/2/2016 05:01:49

isle Posted at 10/31/2016 09:58
Hi bschiett
in the core module ,the 3288 need a 32k clock which is supplied by RTC

thanks - in our application we don't want the linux kernel or rk3288 to sleep, we want it to keep running the same way non stop because it's an industrial application. How does the rk3288 use the 32k clock for temperature protection?

isle · Posted at 11/2/2016 09:56:57

Hi bschiett

here :
QQ截图20161102095113.png

please refer to the chapter of CRU :
http://bbs.t-firefly.com/forum.p ... =275&extra=page%3D1

bschiett · Posted at 11/2/2016 16:59:12

isle Posted at 11/2/2016 09:56
Hi bschiett

here :

OK, thanks so much for the clarification. Does the RTC need to be powered all the time and does it have to be able to wake the CPU? In other words in the reload schematic there is the possibility to attach a battery and the RTC has the possibility to turn the PWR_EN signal on, is this necessary or not for our application?

isle · Posted at 11/3/2016 09:53:48

Hi bschiett
the battery is not necessary.
It need to be attached only if you want the CPU to be started automatically .

bschiett · Posted at 11/4/2016 18:12:20

isle Posted at 11/3/2016 09:53
Hi bschiett
the battery is not necessary.
It need to be attached only if you want the CPU to b ...

Thanks, so the 2nd circuit above to turn on PWR_EN via RTC is not essential?

If the MCU section of the schematic is removed because we don't need IR, this means PWR_EN_SYS will not be pulled high (because there is no MCU_VCC), so basically when the power is plugged in (VCC_SYS present) the user will have to press the POWER switch (SW3) to boot the system, correct? And to switch it off again press the POWER switch?

isle · Posted at 11/7/2016 10:22:26

Hi bschiett
Yes,It is not necessary.

Yes, when the MCU is gone,you can boot the system by press the POWER key.