CommentStreams:D35f5bbb111005de3f9a5f051ea00d36

Although not advertised as compatible, the X728 is working fine when plugged directly into my RPi Zero W. However, I found that if I use a cable and make only the connections specified between the X728 and Pi (Pins 2-6, 29, 31-33) the i2C stops working, so that the clock and battery status functions won't work. After some experimentation I found that connecting pin 1 in addition to the documented pins restores the i2c functions. I'm guessing the X728 is getting the 3.3V voltage level used for the i2c from the Pi. I assume this may be the case for all Pi models. If I'm right, you should add pin 1 to the list of "Pins and GPIO used."