Real Time Clock Module DS1338

HobbyTronics Real Time Clock Module DS1338
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Model: RTC-DS1338
Manufacturer: HobbyTronics
Average Rating: 5 out of 5 Stars!


Real Time Clock Module DS1338

A Real Time Clock Module with battery backup using the easy to use DS1338 chip. The DS1338 is functionally the same as the popular DS1307 chip with the difference being that the DS1338 works at any voltage from 3V to 5V making it easy to use on either 3.3V and 5V systems without modification or logic level conversion. Ideal for your project including Arduino and Raspberry Pi projects.

Makes you wonder why the DS1307 chip is still used?

We have an example Arduino program for reading and writing the module, but any example code available for the DS1307 or DS1338 will work ok.

The module comes fully assembled and pre-programmed with the *approximate* current time (UK Date/Time). The included Lithium coin cell battery (CR1225) will typically run the module for 10 years without external power. The DS1338 is accessed via the I2C protocol and we have added 10K pullup resistors to the SDA and SCL pins.


  • I2C interface
  • 10K I2C pull-up resistors on-board
  • Hour : Minutes : Seconds AM/PM
  • Day, Month, Year
  • Leap year compensation
  • Accurate calendar up to year 2100
  • Battery backup included
  • 1Hz output pin (SQW)
  • 56 Bytes of Non-volatile memory available to user
  • Dimensions: 0.75x0.75" (19x19mm)
  • Two mounting holes


DS1338 Datasheet


Hobbytronics Arduino Example code
Raspberry Pi RTC config
Example 16F88 code
Arduino Tutorial. Thanks John Vaughters!
Bildr Arduino Tutorial


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Real Time Clock Module DS1338
Click to enlarge
Real Time Clock Module DS1338
Click to enlarge
Real Time Clock Module DS1338
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