Saving time with Hardware Clock: Difference between revisions
Sillysausage (talk | contribs) (Created page with "= Install Hardware = I used a [http://www.piface.org.uk/products/piface_clock PiFace Real Time Clock]. After installing the CR1220 battery and correctly mounting on the board...") |
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Add the modules from the kernel | Add the modules from the kernel | ||
== /etc/modules | == /etc/modules == | ||
Add these modules so they're loaded on boot. You can modprobe each one individually if you don't want to reboot. | Add these modules so they're loaded on boot. You can modprobe each one individually if you don't want to reboot. | ||
{{Cat|/etc/modules|i2c_dev | |||
i2c_bcm2708 | i2c_bcm2708 | ||
i2c:mcp7941x | i2c:mcp7941x | ||
}} | |||
== /media/mmcblk0p1/config.txt == | == /media/mmcblk0p1/config.txt == | ||
| Line 21: | Line 21: | ||
Add these two parameters to the bottom | Add these two parameters to the bottom | ||
{{Cat|/media/mmcblk0p1/config.txt|dtparam{{=}}i2c1{{=}}on | |||
dtparam=i2c_arm=on | dtparam{{=}}i2c_arm{{=}}on | ||
}} | |||
{{cmd|mount -o remount,ro /media/mmcblk0p1}} | {{cmd|mount -o remount,ro /media/mmcblk0p1}} | ||
| Line 28: | Line 29: | ||
Then you will need to reboot. | 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: | You will want to make sure the device is created when hwclock starts, if it isn't already created. To the bottom of {{Path|/etc/conf.d/hwclock}} add this: | ||
{{Cat|/etc/conf.d/hwclock|... | |||
if [ | start_pre() { | ||
if [ -d "/sys/class/i2c-adapter/i2c-1/i2c-dev/i2c-1" ]; then | |||
einfo "Creating RTC device"; | einfo "Creating RTC device"; | ||
echo mcp7941x 0x6f > /sys/class/i2c-adapter/i2c-1/new_device | echo mcp7941x 0x6f > /sys/class/i2c-adapter/i2c-1/new_device | ||
fi | fi | ||
}</pre> | } | ||
}} | |||
For the time being this is necessary but in the future when [https://github.com/raspberrypi/linux/issues/1032 issue 1032] you should be able to just add | |||
{{Cat|/media/mmcblk0p1/config.txt|... | |||
dtparam{{=}}i2c-rtc,mcp7941x | |||
}} | |||
to {{Path|/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: | |||
{{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|rc-service hwclock start}} | |||
{{cmd|rc-update add hwclock default}} | |||
If you are running Alpine Linux in the diskless mode (non-persistent root filesystem), save the configuration by: | |||
{{cmd|lbu commit -d}} | |||
[[Category:Hardware]] | |||
[[Category:System Administration]] | |||
[[Category:Raspberry]] | |||
Latest revision as of 13:53, 25 August 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.
Contents of /etc/modules
/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
Contents of /media/mmcblk0p1/config.txt
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:
Contents of /etc/conf.d/hwclock
For the time being this is necessary but in the future when issue 1032 you should be able to just add
Contents of /media/mmcblk0p1/config.txt
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:
rc-service hwclock start
rc-update add hwclock default
If you are running Alpine Linux in the diskless mode (non-persistent root filesystem), save the configuration by:
lbu commit -d