I understand that the Jetson Nano dev board comes with RTC enabled with the addition of a coin cell battery. However, I am looking to use my own RTC chip on a separate board I design that communicates through I2C.
Is there any way to disable the current RTC in the Kernal or device tree and set up a new RTC with hwclock that communicates through I2C? I am familiar with this on the Raspberry pi platform but have no idea how to do it on the Jetson Nano platform.
The RTC chip I am using is the PCF8523 chip. Looking at /usr/src/linux-headers-4.9.140-tegra-ubuntu18.04_aarch64/kernel-4.9/drivers/rtc/Makefile it seems that the rtc-pcf8523.o (i’m assuming the pcf8523 driver file) object file is already build in the kernel.
We tried to add an external rtc module to the Jetson Nano. The rtc module we want to add is the pcf8523 to i2c-0.
We did the same steps as descripted above. We added the lines for the pcf8523 to the dts file we extracted from the Jetson Nano. Afterwards we compiled the dts into a dtb file.
Then we coppied the dtb file to /boot/dtb and added the following line “FDT </boot/thefile.dtb>” to /boot/extlinux/extlinux.conf.
After rebooting no extra rtc module was added in the /dev. We executed the following command “echo pcf8523 0x68 | tee /sys/class/i2c-dev/i2c-0/device/new_device”. No extra rtc module as created in /dev.
What step do we miss the get the rtc module working?