TM1637 4-Digit Display

A 0.36-inch red 4-digit 7-segment display driven by the Titan Micro TM1637 chip over just two signal wires.

What is the TM1637 4-Digit Display?

The TM1637 4-Digit Display is a compact red 7-segment module built around the Titan Micro Electronics TM1637 LED driver and scan-control IC. It packs four digits plus a center colon onto a board roughly 66 x 12 x 27.2 mm (about 10 g), and the entire display is controlled with only two signal lines, CLK and DIO, alongside VCC and GND.

The TM1637 chip handles multiplexing and constant-current segment drive internally, so the host microcontroller only sends digit data over the two-wire serial link instead of refreshing the display itself. The timing resembles I2C (start condition, stop condition, and an ACK the chip asserts by pulling DIO low on the eighth clock), but the protocol carries no device address, so it is not I2C and will not appear on an I2C bus scan. Brightness is adjustable across eight software-selectable levels, plus a display on/off bit. The module runs from a 5V supply (5.5V maximum) and its CLK and DIO lines also tolerate 3.3V logic, so it works with both 5V and 3.3V boards.

Because the driver includes the current-limiting and the module carries onboard pull-ups, very few external parts are needed to get digits on screen. With all segments lit at full brightness the module draws roughly 80 mA. The combination of a built-in colon and two-pin control makes it a common choice for clocks, timers, counters, and sensor readouts. The TM1637 can also scan a small key matrix (up to 16 keys via the DIO line), though most display breakout modules leave that feature unwired.

TM1637 4-Digit Display pinout

Pin	Function	Type
`CLK` CLK	Digital clock	Digital input
`DIO` DIO	Digital data	Bidirectional (GPIO)
`VCC` VCC	Power	Power in
`GND` GND	Power	Power in

Specifications

Operating voltage: 5 V (max 5.5 V)
Interface: digital
Dimensions: 66 × 12 × 27.2 mm

Verified from the Tinkered component library · Titan Micro Electronics / generic breakout module.

Circuit requirements

Four connections only: VCC to 5V, GND to ground, and CLK and DIO to any two digital GPIO pins. No PWM, analog, or dedicated SPI/I2C peripheral is required.
This is not an I2C device. It has no address, so do not use Wire.h or an I2C scanner to find it. Use a dedicated TM1637 library that bit-bangs the two-wire protocol.
The module includes onboard pull-up resistors on CLK and DIO, so external pull-ups are normally unnecessary. DIO is bidirectional (the chip drives it low during ACK and during key scanning), so avoid also driving it hard from the MCU.
Keep the CLK bit-bang rate modest; the TM1637 expects a relatively slow serial clock (on the order of a few hundred kHz maximum), and pushing it faster produces garbled or missing digits.
There is no reset or brightness pin. Display on/off, the eight brightness levels, and the center colon are all set in software through command bytes.
The center colon is not a separate control line. On most modules it is tied to the high (decimal-point) bit of the second digit, so lighting it depends on setting that bit, which differs between libraries.

Board compatibility

The TM1637 4-Digit Display connects to any of the microcontrollers supported in Tinkered. Mind the 5 V logic level on 3.3 V boards.

Common TM1637 4-Digit Display mistakes

Treating it as an I2C device

The TM1637 uses a custom two-wire protocol with I2C-like timing but no address byte. Wiring it to the SDA/SCL pins and calling Wire.begin() will not work, and an I2C scanner will never detect it. Use a TM1637-specific library on ordinary GPIO pins.

Forgetting to turn the display on or set brightness

After power-up the display can stay blank until the host sends a brightness/display-control command with the on bit set. Sending digit data alone is not enough; issue the display-on and brightness command as part of initialization.

Swapping CLK and DIO

The two signal wires are not interchangeable. If CLK and DIO are crossed, nothing meaningful appears. Confirm that each pin in the sketch matches the physical CLK and DIO labels on the module.

Expecting the colon to be a dedicated control

The center colon is driven through the second digit's high bit, not a separate pin or command, so clock projects that ignore that bit show the time without the colon. How you enable it depends on the specific library.

Clocking the interface too fast

The TM1637 is designed for a slow serial clock. Removing the small inter-bit delays or running the CLK line at high speed leads to intermittent, flickering, or scrambled digits. Keep the library's default timing.

TM1637 4-Digit Display datasheet

Official TM1637 4-Digit Display datasheetTitan Micro Electronics / generic breakout module

Popular TM1637 4-Digit Display projects

Digital clock

The four digits and built-in center colon make an HH:MM clock straightforward, usually paired with an RTC such as the DS3231 for accurate timekeeping.

Countdown and countup timer

Kitchen timers, Pomodoro timers, and stopwatches use the colon-separated format and only two GPIO pins, leaving the rest of the board free for buttons and a buzzer.

Sensor value readout

Show temperature, humidity, or another numeric reading from a sensor like a DHT22 or thermistor without wiring a full graphical display.

Voltmeter or ADC monitor

Display a scaled analog reading (battery voltage, potentiometer position, current) as a live four-digit number for quick bench diagnostics.

Scoreboard or counter

Event counters, tally displays, and game scoreboards benefit from bright, readable digits controlled with minimal wiring and code.

Build with the TM1637 4-Digit Display.

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