I have just got i2c working on the BPI-R3
I started with a RPPI Sensor Hat, and connected it via a 26pi extender
when I ran i2cdetect only one of the 6 sensors where found. while on the RPI all where found
I developed my application in C on the RPI. Then added the source it to my BPI-R3 image
It worked. even though it was not detected - the only change I had to make was the i2c bus number
on the RPI i uses bus 1, and on the BPI-R3 i used bus 0