Hardware Reference
In-Depth Information
The Tiny RTC I used came with a 3.6 V battery.) It is claimed that there are mailing
restrictions on batteries to certain countries. So you may want to shop for suitable
batteries while you wait for the mail.
■
Buying a fresh battery ahead of time is recommended, as batteries often arrive
exhausted.
Tip
Figure
4-2
shows a PCB unit that I purchased through eBay. This unit came paired
with the AT24C32 EEPROM chip. The auction was labeled “Tiny RTC I2C Modules.” You
don't have to use this specific PCB, of course. The wiring for each chip is fairly basic and
can be prototyped on a breadboard if you can't find one. But if you do choose this PCB, a
modification is
required
before you attach it to the Raspberry Pi.
Figure 4-2.
An assembled DS1307 PCB purchased through eBay
■
I2C pull-up resistors R
2
and
R
3
must be removed before wiring the PCB to the
Raspberry Pi.
also, if you plan to attach the SQW/oUt output of this pCB to a Gpio input, be
sure to track down and remove its pull-up resistor as well.
Caution
