Adding a battery buffered realtime clock to the Beaglebone Black provides accurate time when no Internet is available. I used an Epson RX8025NB module, and connected it to I2C bus 1. Under Ubuntu 14.04 LTS a set of rtc drivers already exists, and enabling the clock was a simple command. The biggest work was to enable I2C bus 1 on pins P9-17 and 18, and for battery charge protection, soldering the tiny 2mm schottky diodes (SOD-323) into place.

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