chronodot basics

[wild]

I have the chronodot and the arduino mega 2560. I also downloaded the chronodot_clock program. I think I understand the code. But I have the following questions:

Is the address for the DS3231 always 68hex or is it different for each chip? If so, how do I find it?

I have to connect the SDA pin of the chronodot to the arduino mega, but which pin, SDA on the mega? and do I need a pull up resistor?

[Stephanie]

All DS3231 chips have the same 0x68 address.

On the Mega, the I2C pins are 20 and 21. Recent Megas have this indicated on the silkscreen, "SDA 20 SCL 21' is printed on them next to the header.

You do have to have pullup resistors on both SDA and SCL lines, that is part of how I2C works. However, recent megas (or maybe all Megas) have 10K pullups on them already, but it would not hurt for you to add your own pullup resistors to the Chronodot.

If your Mega looks like the one in this picture, then you can just plug the chronodot in to the SDA and SCL lines (and 5v and Gnd too of course) and not worry about adding pullup resistors:
http://arduino.cc/en/uploads/Main/Ardui ... _Front.jpg

Cheers!

[pburgess]

Is the address for the DS3231 always 68hex or is it different for each chip?

It will always be 0x68.

I have to connect the SDA pin of the chronodot to the arduino mega, but which pin, SDA on the mega? and do I need a pull up resistor?

The I2C pins on the Mega are 20 (SDA) and 21 (SCL). Shouldn't need pullups...the Wire library enables the Arduino's internal pullups on these pins.

[wild]

Thanks, that works.