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PiSugar3 RTC

All PiSugar 3 models have an MCU-emulated DS3231-compatible RTC, which can be used with hwclock.

Function description

address: 0x68 as same as ds3231

Data description: The clock part is consistent with ds3231

Using PiSugar RTC as the system clock​

The following steps use Raspberry Pi OS with kernel 5.15 as an example. For other systems, consult their DS3231 configuration instructions.

  1. Enable the I2C interface.

  2. Upgrade the PiSugar firmware to the latest version.

  3. Open the Raspberry Pi boot configuration file:

    • Raspberry Pi OS Bookworm and later: /boot/firmware/config.txt
    • Older Raspberry Pi OS releases: /boot/config.txt

    Add the following line under the global [all] section (or outside any model-specific section):

    [all]
    dtoverlay=i2c-rtc,ds3231

    If the file already contains an [all] section, add only the dtoverlay line to that section. Do not add the overlay more than once.

  4. Save the file and restart the system:

    sudo reboot

After the restart, the RTC should be registered by the system. You can use the following commands to verify it.

Use the following command to inspect the I2C bus:

i2cdetect -y 1

The UU mark at address 0x68 indicates that the RTC address is in use by a kernel driver.

pi@PI4B:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- 57 -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Install and use hwclock​

Some minimal Raspberry Pi OS images do not include hwclock. If the command is missing, install it with:

sudo apt update
sudo apt install util-linux-extra

You can then read the RTC, write the current system time to it, and read it again:

pi@PI4B:~ $ sudo hwclock -r
2020-01-22 08:00:27.671798+08:00
pi@PI4B:~ $ sudo hwclock -w
pi@PI4B:~ $ sudo hwclock -r
2022-08-31 13:14:31.619253+08:00
pi@PI4B:~ $