The module contains a DALLAS DS1307 chipconstituting the real time clock ( RTC ), as well as an ATMEL 24C32 EEPROM memory ( 4Kbytes )
The assembly generally communicates with any micro-controller-based system via the I²C bus
This module has 4 particularities:
- It does not have a 3V CR2032 Lithium battery, but a LIR2032 rechargeable lithium battery, as well as its charging circuit
- The address of the EEPROM memory cannot be modified because there are no coding jumpers.
Pins A0, A1, A2 are connected to 0v. The binary address is therefore fixed at 1010000X (i.e. $ A0 in hexadecimal), X being the R / W bit.
- The location of resistor R7 ( quartz polarization in pin 2 ) is empty, this is normal and the module works perfectly like this
- The location for U1 is empty, it can accommodate a "One-Wire" temperature sensor ( not supplied ) such as a DALLAS DS1820, or DS18B20, etc ...
I carried out measurements on the module, on 2 particular points:
- TP1: + 4.43V -> voltage present at the terminals of the LIR2032 battery, with or without supply voltage + 5V !!!
This remains correct because indeed, the manufacturer of this battery indicates a nominal charging voltage of 4.20V with a constant current of 17mA, see the datasheet.
- TP2: + 3.195V -> the DALLAS datasheet recommends a V BAT voltage between 2.0 and 3.5V
The V BAT voltage supplied to the DS1307 therefore fully complies with the manufacturer's information, see the datasheet.
Fully charged, the battery can power the DS1307 to provide the time ( date and time ) for 1 year.
The module can of course be mounted in cascade with other I²C peripherals, provided that the addresses of each are respected ( no duplicate addresses ... ).
You can skip the rechargeable battery if it does not suit you, and replace it with a CR2032 battery, then proceed as follows:
- Remove resistors R4 / R5 / R6 as well as diode D1
- Replace the resistor R6 with a strap
- Replace LIR2032 battery with CR2032 battery
Dimensions : 27 x 28 x 8.4mm (W x D x H)
→ I bought this module here in December 2015 for 1.12 € ( free shipping ).