R2 + centos image + i2c RTC ds3231 = not work (((

Hi !

I try using ds3231 RTC with R2. i2c enabled by “modprobe i2c”. Installed i2c-tools.

i2cdetect not detect any devices at 0x68 on 0,1,2 or 3 buses.

Wich bus used via GPIO header (GPIO 2,3) ? Bus 1 ? at R2 GPIO pinout 2 and 3 pins labeled I2C1_SDA.


you can refer to below link http://forum.banana-pi.org/t/has-anyone-added-an-rtc/5004

Thank you, I already readed this topic. Now I try using Ubuntu 16.04 image and once I detect successfull my hwclock module (ds3231) at bus 1 by 0x68 address. But only once…

In my test i did not found module,but i had successful read amd wrote from/to it…but i used kernel 4.14 (official images using 4.4 where access to gpio is bit different).i don’t know if i2c is already enabled in 4.4 dts

i2c in 4.4 is enabled by default.

By i2cdump at bus 1 I can manual read data from ds3231 module: i2cdump -y 1 0x68

but i2cdetect not found any device at 0x68…

The address 00h contains data about seconds - they are constantly changing.

I try manual create RTC device, but unfortunately…

echo ds3231 0x68 > /sys/class/i2c-adapter/i2c-1/new_device

How you read and wrote from/to hwclock ?


I has also not found the device via i2cdetect,but i had accessed it


Clock functions i have done with hwclock

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My Ubuntu image not contain rtc-ds1307 driver. I download BSP, but not found this device in kernel config… where is ?

Why using old 4.4? Anyway in menuconfig you can search with “/”

I already find RTC support and ds1307 driver. Now I successfull enable RTC support in BSP and enable rtc-ds1307 module driver. Recompile and update kernel/u-boot.

And hardware clock is sucessfull work !!!

GPIO header I2C bus in BPI-R2 work at bus 1 !!! i2cdetect not detect ds3231, but ds3231 work fine. You see module dump by “i2c-dump 1 0x68 1” - 1st byte is seconds of current time. CentOS and Ubuntu images not enabled RTC support by default - need download BSP and reconfigure kernel/u-boot and compile driver for RTC.

frank-w, thank you very much for you support !