CrossRoads:
Is there a standard for I2C?
Not really. It is a mess.
I have seen several different 4 pin "i2c" headers/connectors.
I have devices & shields with these pinouts:
- gnd, power, data, clock
- gnd, power, clock, data
- power, gnd, data, clock
- ground, data, clock, power
- ground, clock, data, power
What I've noticed is that
- gnd, power, data, clock
seems to be fairly popular.
It is used on the Itead "duino" boards I showed above, UNO & Mega sensor shields,
and most of the i2c devices I have like, ebay DS1307 & DS3231 RTC modules, hd44780 LCD backpacks, etc...
Pull up some ebay devices and have a look.
(search for "arduino i2c")
Most of what I see for UNO/Mega sensor shields, lcd backpacks and RTC modules is
- gnd, power, data, clock
While that is my favorite pinout,
there are other devices out there that use other pinouts, so
depending on what devices people have,
they may have a different preference.
--- bill