Ok, i need to revive this thread because something is wrong with this information/instructions or wrong with my cb2.
Recently i needed to have this external rtc attached and working on my CB2 but for some reason or the lack of knowledge (hardware) from me, did not work! And perhaps it will not work as expected.
I have followed this instructions verbatim (double checked, triple checked) and i have the following issue:
* if i turn OFF the CB2, the rtc is not detected on next boot, but i can see i2c finds the rtc at the address.
* if i reboot the CB2, everything works as expected, i can set the date and time and the next reboot i get the correct date and time.
At fisrt, i had a similar rtc module, not the exact one pointed by Benn.
After many troubles and tries i gave up with this one and ordered the one from the link, and same problem.
I googled and found DS1307 needs 5v as VCC input, i measured the UART Debug Port's VCC on my cb2 to have 3.25v and i think that is the source of problem.
For some reason, both rtc modules don't have a level shifter, if they do i don't know how to turn it on , or worse the UART Debug Port's VCC should be 5v and mine is 3.25v.
I can measure during reboot that the UART Debug Port's VCC is never 0v ( stays at ~0.52v )and that could trigger the rtc module to be detected.
Does any one have this setup working? (using 3.25v)
Can you suggest some work around? I don't have any 5v pin available, unless i can share it and it is safe to do it.
PS: i just found CB1 UART Debug Port's VCC runs on ~3.81v!!
Update: used 5v as input, still the same.