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# TM1637 4-Digit Display with an Arduino Uno

The TM1637 is specified for 5 V plus or minus 10 percent, which the Arduino Uno's 5V pin meets and 3.3 V boards do not. Its CLK and DIO take D2 and D3 here, driven by a library in software: it is not I2C, so it neither uses nor blocks the Uno's A4 and A5.

## Wiring

| TM1637 4-Digit Display | Arduino Uno | Note |
| --- | --- | --- |
| CLK | D2 |  |
| DIO | D3 |  |
| VCC | 5V |  |
| GND | GND |  |

## What to know on the Arduino Uno

- Its 5 V ± 10 % supply rating (4.5 V to 5.5 V) fits the Uno's 5V exactly, and its inputs then see the Uno's full 5 V logic swing. (Titan Micro TM1637 datasheet V2.1, p. 1)
- The chip takes a clock up to 500 kHz, and the library bit-bangs it far below that on the Uno, so CLK and DIO can be any two digital pins. D2 and D3 are the Uno's interrupt pins; if a sensor needs them, move the display to pins such as D7 and D8 and change CLK and DIO. (Titan Micro TM1637 datasheet V2.1, p. 2)
- Because the protocol has no address, it cannot share pins with another device, but it also cannot clash with the Uno's I2C parts: an I2C scan on A4 and A5 will never find it. (Titan Micro TM1637 datasheet V2.1, p. 2)

## Code

Libraries: seeed-studio/Grove 4-Digit Display

```cpp
// TM1637 4-Digit Display on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/tm1637-4digit-display/arduino-uno
#include <TM1637.h>

#define CLK 2
#define DIO 3

TM1637 tm(CLK, DIO);

void setup() {
  tm.init();
  tm.set(BRIGHT_TYPICAL);          // 0-7; nothing lights until this is sent
}

void loop() {
  static int n = 0;
  tm.display(0, (n / 1000) % 10);
  tm.display(1, (n / 100) % 10);
  tm.display(2, (n / 10) % 10);
  tm.display(3, n % 10);
  tm.point(n % 2 ? POINT_ON : POINT_OFF);   // colon blinks once a second
  n = (n + 1) % 10000;
  delay(1000);
}
```

Compiled for arduino:avr:uno on 2026-10-30.

## Questions

### Can I run a TM1637 display from an Arduino Uno's 5V?

Yes, that is its specified supply: 5 V ± 10 % (TM1637 datasheet, p. 1). VCC to 5V, GND to GND, CLK and DIO to any two digital pins.

### Why doesn't my TM1637 show up on an I2C scanner on the Uno?

It is not an I2C device. It uses its own two-wire protocol with no address, driven on ordinary digital pins (D2 and D3 here), so I2C scanners never see it.

### Which Uno pins can the TM1637 use?

Any two digital pins. The example uses D2 for CLK and D3 for DIO; pick others if you need D2 and D3 for interrupts.

## More

- [TM1637 4-Digit Display reference](https://www.tinkered.ai/components/tm1637-4digit-display.md): pinout, specs, rules and common mistakes

## Try it

Tinkered simulates the TM1637 4-Digit Display on the Arduino Uno in the browser, with this wiring and code, free: https://www.tinkered.ai/components/tm1637-4digit-display/arduino-uno