Saving time with Hardware Clock: Difference between revisions
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== Starting hwclock on boot == | |||
The hwclock service needs to be started for the hardware clock device to actually do anything. Check if hwclock has been started by running this command: | |||
{{cmd|rc-status {{!}} grep hwclock}} | |||
If it outputs | |||
<pre> hwclock [ started ]</pre> | |||
hwclock has already started. Otherwise start it manually and add it to the default init.d runlevel, so that it starts at boot time: | |||
{{cmd|sudo rc-service hwclock start}} | |||
{{cmd|sudo rc-update add hwclock default}} | |||
If you are running Alpine Linux in the diskless mode (non-persistent root filesystem), save the configuration by: | |||
{{cmd|sudo lbu commit -d}} | |||
[[Category:Hardware]] | [[Category:Hardware]] | ||
[[Category:System Administration]] | [[Category:System Administration]] | ||
[[Category:Raspberry]] | [[Category:Raspberry]] |
Revision as of 14:45, 4 February 2023
Install Hardware
I used a PiFace Real Time Clock. After installing the CR1220 battery and correctly mounting on the board, see manual for that.
Install Software
Add the modules from the kernel
/etc/modules/
Add these modules so they're loaded on boot. You can modprobe each one individually if you don't want to reboot.
i2c_dev i2c_bcm2708 i2c:mcp7941x
/media/mmcblk0p1/config.txt
You will need to mount this as read-write
mount -o remount,rw /media/mmcblk0p1
Add these two parameters to the bottom
dtparam=i2c1=on dtparam=i2c_arm=on
mount -o remount,ro /media/mmcblk0p1
Then you will need to reboot.
Binding the hardware clock device
You will want to make sure the device is created when hwclock starts, if it isn't already created. To the bottom of /etc/conf.d/hwclock add this:
start_pre() { if [ -d "/sys/class/i2c-adapter/i2c-1/i2c-dev/i2c-1" ]; then einfo "Creating RTC device"; echo mcp7941x 0x6f > /sys/class/i2c-adapter/i2c-1/new_device fi }
For the time being this is necessary but in the future when issue 1032 you should be able to just add
dtparam=i2c-rtc,mcp7941x
to /media/mmcblk0p1/config.txt
Starting hwclock on boot
The hwclock service needs to be started for the hardware clock device to actually do anything. Check if hwclock has been started by running this command:
rc-status | grep hwclock
If it outputs
hwclock [ started ]
hwclock has already started. Otherwise start it manually and add it to the default init.d runlevel, so that it starts at boot time:
sudo rc-service hwclock start
sudo rc-update add hwclock default
If you are running Alpine Linux in the diskless mode (non-persistent root filesystem), save the configuration by:
sudo lbu commit -d