查看“How to use the RTC”的源代码

__TOC__
<br />

==Purpose==

This article describes how to use the RTC. The RTC overview is described in the [[RTC overview]] article. <br/>

== How to set a hardware clock using the hwclock tool ==

The correct system time must first be set with the date command. Type the date command to see the date and time format of the string:

 {{Board$}} date
 Fri Mar  9 12:18:51 UTC 2018

 {{Board$}} date --set="Fri Mar  9 19:18:51 UTC 2018"
 Fri Mar  9 19:18:51 UTC 2018

Set the hardware clock to this date:
 {{Board$}} hwclock
 Fri Mar  9 12:21:03 2018  0.000000 seconds
 
 {{Board$}} hwclock --systohc --utc
 
 {{Board$}} hwclock
 Fri Mar  9 19:19:52 2018  0.000000 seconds

See <ref name="date">http://man7.org/linux/man-pages/man1/date.1.html</ref> for more about date settings.
See <ref name="hwclock">http://man7.org/linux/man-pages/man8/hwclock.8.html</ref> for more about hwclock settings.

== How to set an alarm ==
 {{highlight|# disable the alarm}}
 {{Board$}} echo 0 > /sys/class/rtc/rtc0/wakealarm

 {{highlight|# calculate alarm with 1 minute later}}
 {{Board$}} wakeuptime=`date -d "1 minute" +%s`

 {{highlight|# set the alarm}}
 {{Board$}} echo $wakeuptime > /sys/class/rtc/rtc0/wakealarm
 root@stm32mp1:~# [  829.279019] rtc rtc0: Alarm occurred

You can also set an alarm 'n' seconds later:
 {{Board$}} echo +10 > /sys/class/rtc/rtc0/wakealarm

== How to set an alarm and go into a system sleep state with the rtcwake tool ==
 {{highlight|# calculate an alarm 1 minute later}}
 {{Board$}} wakeuptime=`date -d "1 minute" +%s`

 {{highlight|# set wakeup on /dev/rtc0}}
 {{Board$}} rtcwake -lt$wakeuptime -m mem
 rtcwake: wakeup from "mem" using /dev/rtc0 at Sun Mar 11 10:48:06 2018
 [  154.022303] PM: suspend entry (deep)
 [  154.024421] PM: Syncing filesystems ... done.
 [  154.037258] Freezing user space processes ... (elapsed 0.001 seconds) done.
 [  154.044397] OOM killer disabled.
 [  154.047555] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
 [  154.055039] Suspending console(s) (use no_console_suspend to debug)

One minute later...
 NOTICE:  CPU: STM32MP157CAA Rev.B
 NOTICE:  Model: STMicroelectronics STM32MP157C eval daughter on eval mother
 NOTICE:  Board: MB1263 Var1 Rev.C-01
 INFO:    Reset reason (0x810):
 INFO:    System exits from STANDBY
 INFO:    Using SDMMC
 INFO:      Instance 1
 INFO:    Boot used partition fsbl1
 INFO:    Product_below_2v5=1: HSLVEN update is
 INFO:      destructive, no update as VDD>2.7V
 NOTICE:  BL2: v2.0(debug):v2.0-stm32mp-19-01-29
 NOTICE:  BL2: Built : 15:58:42, Jan 29 2019
 INFO:    BL2: Doing platform setup
 INFO:    PMIC version = 0x10
 INFO:    RAM: DDR3-1066/888 bin G 2x4Gb 533MHz v1.41
 INFO:    BL2 runs SP_MIN setup
 INFO:    BL2: Loading image id 4
 INFO:    Loading image id=4 at address 0x2ffe5000
 INFO:    Image id=4 loaded: 0x2ffe5000 - 0x30000000
 INFO:    BL2: Skip loading image id 5
 INFO:    read version 0 current version 0
 NOTICE:  BL2: Booting BL32
 INFO:    Entry point address = 0x2ffe5000
 INFO:    SPSR = 0x1d3
 INFO:    PMIC version = 0x10
 NOTICE:  SP_MIN: v2.0(debug):v2.0-stm32mp-19-01-29
 NOTICE:  SP_MIN: Built : 15:58:42, Jan 29 2019
 INFO:    ARM GICv2 driver initialized
 INFO:    stm32mp HSI (18): Secure only
 INFO:    stm32mp HSE (20): Secure only
 INFO:    stm32mp PLL2 (27): Secure only
 INFO:    stm32mp PLL2_R (30): Secure only
 INFO:    SP_MIN: Initializing runtime services
 INFO:    SP_MIN: Preparing exit to normal world
 [  154.074319] dwc2 49000000.usb-otg: suspending usb gadget configfs-gadget
 [  154.196804] Disabling non-boot CPUs ...
 [  154.250046] CPU1 killed.
 [  154.251704] Enabling non-boot CPUs ...
 [  154.252697] CPU1 is up
 [  154.254885] rtc rtc0: Alarm occurred
 [  154.273940] dwmac4: Master AXI performs any burst length
 [  154.273972] stm32-dwmac 5800a000.ethernet eth0: No Safety Features support found
 [  154.276938] usb usb2: root hub lost power or was reset
 [  154.284703] dwc2 49000000.usb-otg: resuming usb gadget configfs-gadget
 [  154.491151] dwc2 49000000.usb-otg: new device is high-speed
 [  154.619589] dwc2 49000000.usb-otg: new device is high-speed
 [  154.669343] usb 2-1: reset high-speed USB device number 2 using ehci-platform
 [  154.697272] dwc2 49000000.usb-otg: new address 2
 [  154.722774] configfs-gadget gadget: high-speed config #1: c
 [  155.066198] OOM killer enabled.
 [  155.069339] Restarting tasks ... done.
 [  155.075470] PM: suspend exit

See <ref name="rtcwake">http://man7.org/linux/man-pages/man8/rtcwake.8.html</ref> for more about rtcwake settings.

==References==
<references/>

<noinclude>
[[Category:RTC|3]]
{{PublicationRequestId |15042 | 2020-02-21}}
</noinclude>