TM1637 4-Digit 7-Segment Display
Simple 2-wire numeric display for clocks and counters.
The TM1637 drives a 4-digit 7-segment display (almost always with a center colon for clock displays) over a 2-wire protocol that looks like I2C but isn't quite — it uses its own bit-banged timing rather than the standard I2C peripheral, which is why it needs a dedicated software library instead of Wire.h. The chip also has a built-in keypad-scan input, though most hobbyist breakout modules don't wire up the buttons for it.
Its main appeal over the MAX7219 is simplicity for small digit counts: only two signal wires (CLK, DIO) instead of three, no external current-limiting resistor to worry about, and a one-line brightness call. It's the natural choice for clocks, timers, and simple 4-digit counters where you don't need the MAX7219's cascading or larger digit count.
Specifications
| Digits | 4 x 7-segment digits, most modules include a center colon (:) |
| Operating voltage | 3.3V - 5V DC |
| Interface | 2-wire (CLK, DIO) — I2C-like bit-banged protocol, not standard I2C |
| Brightness | 8 software-adjustable levels via a single library call |
| Extra hardware feature | Built-in key-scan input for a keypad matrix (unused on most breakout modules) |
Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | CLK | Clock line for the TM1637 protocol |
| 2 | DIO | Bidirectional data line for the TM1637 protocol |
| 3 | VCC | Power, 3.3V-5V DC |
| 4 | GND | Ground |
Despite the CLK/DIO naming looking like I2C SCL/SDA, do not wire this to a shared I2C bus or drive it with Wire.h — the timing is proprietary to the TM1637 and will not respond to standard I2C transactions. Use a dedicated library (TM1637Display by Avishorp, or similar) which bit-bangs the correct timing on any two GPIO pins.
Variants
The colon on the standard 4-digit module is wired as one shared segment, not two independent dots, so you can only turn it fully on or off, not blink each dot separately. If a design needs true HH:MM:SS with no digit limit, the 6-digit variant uses the same TM1637Display-style library calls with no protocol changes.
| Variant | Temp range | Hum range | Accuracy | Protocol | Price |
|---|---|---|---|---|---|
| TM1637 4-Digit (with colon) | ~$1-3 | ||||
| TM1637 6-Digit | ~$3-5 |