Jetson/RTC

Basic strategy


To add a Real-Time-Clock module to your Jetson TK1 so that it remembers the time and it is fairly accurate, simply follow Santyago's great How-To posted on the forum.

"https://devtalk.nvidia.com/default/topic/769727/embedded-systems/-howto-battery-backup-rtc/"


 * Use Santyago's Grinch Custom Kernel 19.3.4 or above
 * Use an RTC module (Dallas DS3231)
 * Connect the RTC module on Jetson TK1's I2C bus

Custom Kernel
Install Santyago's Grinch Custom Kernel.

"https://devtalk.nvidia.com/default/topic/766303/embedded-systems/-customkernel-the-grinch-19-3-7-for-jetson-tk1/"

RTC Module
In the How-To, Santyago shows how to wire Maxim's DS3231, a high precision I²C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. While it is possible to get the chip and wire everything by yourself, it is easier to just get a module that has the same chip.

There seems to be couple of options. You can get an RTC module with DS3231 from Adafruit, DealExtreme and some other. DS1307 based RTC module might work, but have not tried.

I used a module from a shop in Japan, this one seems to be originally made for Raspberry Pi. The interface is simple. It's just I2C, so all you need to care is VCC, GND and pins for I2C (SCL and SDA).

Connection and Securing the module on the board


I made wiring from the RTC module to back of the J3A1 headers, so that you can still insert some other things for expansion. There are GND, VCC, SCL and SDA pins from Pin #14 to #20 of J3A1 header in one row.

The RTC module from Victory7 had a 2.54mm-pitch 4-pin header to go into a breadboard. I took them out for easy mounting. (Wish this in 2mm-pitch and in the same order as pins on the J3A1 header)



And I just used double-sided adhesive tape to paste the module board on top of the plastic part of the RS232 connector.





Setup
Make sure to go though all the setup procedure explained in Santyago's How-To. "https://devtalk.nvidia.com/default/topic/769727/embedded-systems/-howto-battery-backup-rtc/"

Once everything is done, you turn off Jetson TK1, remove the Ethernet connection and turn it back on, and you will see the correct date and time on the system!

Trouble shooting
If the date appears to not set correctly when run in the /etc/rc.local script, try disabling the contents of the /etc/init/hwclock.conf script. It sometimes interferes with the hwclock setting the computer's date.