View source for Zero/dev/RTC module ds3231

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 [[Zero | Radxa Zero]] > [[zero/dev | Development]] > [[zero/dev/RTC module ds3231| RTC module ds3231 ]]


==== enable i2c overlay ====
use rsetup to enable I2C_EE-M3
if you don't know how to use rsetup, you can refer  [[https://wiki.radxa.com/Rockpi4/dev/use-rsetup-to-enable-common-interface-with-kernel-5.10 here]]

==== pin ====

<pre>
zero                 ds3231
pin 3                sda
pin 5                scl
gnd                  gnd
vcc                   vcc
</pre>

then reboot your Radxa Zero
==== checkout device ====

* make sure that i2c_ee-m3 was enabled
<pre>
root@radxa-zero:/home/radxa# ls /dev/i2c-*
/dev/i2c-3  /dev/i2c-5
</pre>

* check the i2c address of the RTC module

<pre>
root@radxa-zero:/home/radxa# i2cdetect -r -y 3
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- UU -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- -- 
</pre>

==== add a new rtc device ====

* add a new rtc device
<pre>
root@radxa-zero:/home/radxa# echo ds3231 0x68 | sudo tee  /sys/class/i2c-adapter/i2c-3/new_device
</pre>

* checkout the new rtc device 
<pre>
root@radxa-zero:/home/radxa# ls /dev/rtc*
/dev/rtc  /dev/rtc0 /dev/rtc1
</pre>

==== read time from rtc module ====
<pre>
root@radxa-zero:/home/radxa# hwclock -r -f /dev/rtc1
2000-01-01 00:01:40.083622+08:00
</pre>

==== set time ====

<pre>
root@radxa-zero:/home/radxa# apt-get install ntp -y
root@radxa-zero:/home/radxa# sudo service ntp start

or
date -s "2023-05-09 15:16:35"

</pre>


==== write time to rtc module ====
* write time to rtc module after you make sure the time of linux is right
<pre>
root@radxa-zero:/home/radxa# hwclock -w -f /dev/rtc1
</pre>

* then read the hardware RTC at the time to see if it is correct
<pre>
root@radxa-zero:/home/radxa# hwclock -r -f /dev/rtc1
2023-05-09 15:18:45.390726+08:00
</pre>

* to set the Linux system time to the hardware RTC time
<pre>
 hwclock -s -f /dev/rtc1
</pre>

* use timedatectl to view all the time information
<pre>
root@radxa-zero:/home/radxa# timedatectl
               Local time: Tue 2023-05-09 15:21:49 CST
           Universal time: Tue 2023-05-09 07:21:49 UTC
                 RTC time: Thu 1970-01-01 00:04:27
                Time zone: Asia/Shanghai (CST, +0800)
System clock synchronized: no
              NTP service: n/a
          RTC in local TZ: yes

Warning: The system is configured to read the RTC time in the local time zone.
         This mode cannot be fully supported. It will create various problems
         with time zone changes and daylight saving time adjustments. The RTC
         time is never updated, it relies on external facilities to maintain it.
         If at all possible, use RTC in UTC by calling
         'timedatectl set-local-rtc 0'.

</pre>

==== set automatic startup ====

<pre>
root@radxa-zero:/home/radxa# touch /etc/rc.local
root@radxa-zero:/home/radxa# chmod 777 /etc/rc.local
root@radxa-zero:/home/radxa# cat /etc/rc.local
#! /bin/bash

echo ds3231 0x68 | sudo tee  /sys/class/i2c-adapter/i2c-3/new_device
sudo hwclock -s -f /dev/rtc1 

</pre>