Please forgive another newbie question:
In the absence of a tinyduino native RTC, which I know is in the works, I need to use a Chronodot RTC communicating via I2C to SDA (analog input pin A4) and SCL (analog input pin A5). According to my reading, I²C uses open-drain IO pins, so pull-up resistors on the SCA and SCL lines are generally required. But confusingly I have read that the Wire library, which does the
I2C communication, enables internal pull-up resistors by default. More confusing for a newbie like me, I see photos of projects on the web, where people are using chronodots RTCs with other 3.3v boards like the pro mini, with no sign that they have installed the pullups, but they still seem to be working.
Do the SCL and SDA lines on the tinyduino have internal pull-up resistors that are automatically enabled by the wire library, or do I need to run my own 4.7KΩ(?) resistors from the SCA pin to VCC, and the SCL pin to VCC.
And finally, my final unit will also have the Tiny-circuits accelerometer in it, which is also an I2C device with a level shifter. Does the presence of that level shifter, affect this question? Ie, does the level shifters connection to the SCL & SDA lines mean I dont have to worry about pulling up SCA & SCL for the other I2C devices that would also be connected?