DS3231 — i2c address & wiring
Temperature-compensated real-time clock, very low drift.
Key facts
DS3231 at a glance
| i2c address | 0x68 fixed address |
|---|---|
| Logic voltage | 3.3–5 V |
| Type | rtc |
| Part | Maxim DS3231 |
| Ships with | Qwiic, STEMMA QT |
| Datasheet | Maxim DS3231 — manufacturer documentation ↗ |
The chip
What the Maxim DS3231 actually is
High-accuracy real-time clock (RTC) featuring an integrated temperature-compensated crystal oscillator (TCXO), battery-backed timekeeping, programmable alarms, square-wave output and a 32.768 kHz reference output. Keeps calendar time far more accurately than RTCs relying on an external crystal.
Watch out: The popular ZS-042 module includes a crude charging circuit meant for a rechargeable LIR2032 cell. Fit a normal CR2032 and the module tries to charge it anyway — a genuine hazard. Use a LIR2032, or break the charge path (remove the charging resistor or diode) before inserting a non-rechargeable cell.
Wiring
How to connect the DS3231
The DS3231 talks i2c at address 0x68. It runs at 3.3–5 V, so match your host's logic level — if your host is 5 V and a board on the bus is 3.3 V-only, add a level shifter. Use the compatibility checker to confirm the exact cable for your setup.
The address is fixed, so two DS3231s can't share a bus directly — the address-conflict guide covers the workarounds (multiplexer, second bus).
Wiring is the usual four: power, ground, SDA and SCL, plus pull-up resistors — almost always already fitted on the breakout. Nothing showing up? Run an i2c scan first; if the bus is silent, the 7-step checklist finds it faster than guessing.
Ecosystems
Plug-together options for the DS3231
DS3231 breakouts ship with Qwiic and STEMMA QT — keyed 4-pin cables carrying power, ground, SDA and SCL, so there's nothing to solder and nothing to wire backwards. Chain it to the next board and keep going.
Running a mixed bench? Those ecosystems interoperate more than their marketing suggests — see every connector pairing for the cable or adapter you need, or the standards overview for how they compare.
Go deeper
Guides covering the DS3231
Watch the bus
Boards that clash with the DS3231
These want an address the DS3231 also answers (0x68), so they can't share a bus with it untouched. If one is address-selectable, strap it elsewhere; if not, the conflict guide covers the multiplexer and second-bus routes, and the collision roundup explains why a scan won't warn you.
Get one
Questions
DS3231 i2c FAQ
What is the DS3231's i2c address?
The DS3231 sits at a fixed address of 0x68. It can't be changed, so two of them can't share one bus without a multiplexer or a second bus.
What voltage does the DS3231 run at?
3.3–5 V logic. That range covers both 3.3 V and 5 V hosts, so it drops onto a Pi, ESP32 or Arduino without a level shifter.
Can I use two DS3231s on one i2c bus?
Not directly — every DS3231 answers to 0x68, so two on one bus would collide. Use a TCA9548A multiplexer to give each its own channel, or put the second one on a separate bus.
Does the DS3231 work with Qwiic and STEMMA QT?
Yes — DS3231 breakouts ship with Qwiic / STEMMA QT, so it plugs straight in with no soldering. Mixing ecosystems? The compatibility checker gives you the exact cable or adapter.
What should I watch out for with the DS3231?
The popular ZS-042 module includes a crude charging circuit meant for a rechargeable LIR2032 cell. Fit a normal CR2032 and the module tries to charge it anyway — a genuine hazard. Use a LIR2032, or break the charge path (remove the charging resistor or diode) before inserting a non-rechargeable cell.