Arduino TM1637 4-Digit Display: Wiring, Code and Simulator

To build this Arduino TM1637 4-Digit Display project you need an Arduino Uno and a TM1637 4-digit display. A TM1637 counter on two wires, with the start, stop and acknowledge bits written by hand. Make the 4 connections in the wiring table, upload the Arduino C++ code, and open the logic analyzer on CLK and DIO to see each byte and its ACK.

Open this circuit in the free Arduino Uno simulator

Parts list

Qty	Part	What it does
1	Arduino Uno	the microcontroller board
1	TM1637 4-digit display	Four digits on two wires, CLK and DIO (LSB first, ACK after each byte). 0x40, then 0xC0 and four segment bytes, then 0x8F to switch on.

Wiring

#	From	To
1	Arduino Uno pin 2	TM1637 4-digit display CLK
2	Arduino Uno pin 3	TM1637 4-digit display DIO
3	Arduino Uno 5V	TM1637 4-digit display VCC
4	Arduino Uno GND	TM1637 4-digit display GND

Step by step

Open the simulator. Open the BitForBytes Embedded Lab in your browser and start from the Arduino Uno. No install or account is needed.
Add the parts. Add a TM1637 4-digit display from the parts palette.
Wire 1. Connect Arduino Uno pin 2 to TM1637 4-digit display CLK.
Wire 2. Connect Arduino Uno pin 3 to TM1637 4-digit display DIO.
Wire 3. Connect Arduino Uno 5V to TM1637 4-digit display VCC.
Wire 4. Connect Arduino Uno GND to TM1637 4-digit display GND.
Paste the Arduino C++ code. Paste the Arduino C++ code below into the code editor.
Run it. Press Run. Open the logic analyzer on CLK and DIO to see each byte and its ACK.

Arduino C++ code

// 4-digit display: a TM1637 on two wires (CLK 2, DIO 3), bit-banged by hand.
// Like I2C without an address, and least significant bit first.
const int CLK = 2, DIO = 3;
const byte DIGITS[10] = {0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F};

void pinLow(int p) { pinMode(p, OUTPUT); digitalWrite(p, LOW); }
void pinHigh(int p) { pinMode(p, INPUT_PULLUP); }  // released: the pull-up raises it

void start() { pinHigh(DIO); pinHigh(CLK); delayMicroseconds(5); pinLow(DIO); delayMicroseconds(5); }
void stop() { pinLow(CLK); pinLow(DIO); delayMicroseconds(5); pinHigh(CLK); delayMicroseconds(5); pinHigh(DIO); }

void writeByte(byte b) {
  for (int i = 0; i < 8; i++) {
    pinLow(CLK);
    if (b & 1) pinHigh(DIO); else pinLow(DIO);
    delayMicroseconds(5);
    pinHigh(CLK);
    delayMicroseconds(5);
    b >>= 1;
  }
  pinLow(CLK);  // ninth clock: the chip pulls DIO low to acknowledge
  pinHigh(DIO);
  delayMicroseconds(5);
  pinHigh(CLK);
  delayMicroseconds(5);
  pinLow(CLK);
}

void show(int n) {
  start(); writeByte(0x40); stop();                 // write data, auto-increment
  start(); writeByte(0xC0);                         // from digit 0
  writeByte(DIGITS[(n / 1000) % 10]);
  writeByte(DIGITS[(n / 100) % 10]);
  writeByte(DIGITS[(n / 10) % 10]);
  writeByte(DIGITS[n % 10]);
  stop();
  start(); writeByte(0x8F); stop();                 // display on, full brightness
}

void setup() {}

void loop() {
  static int n = 0;
  show(n);
  n = (n + 1) % 10000;
  delay(200);
}

What to try

Open the logic analyzer on CLK and DIO to see each byte and its ACK.

Frequently asked questions

How do I wire the TM1637 4-Digit Display project on an Arduino Uno?

Make 4 connections: Arduino Uno pin 2 to TM1637 4-digit display CLK; Arduino Uno pin 3 to TM1637 4-digit display DIO; Arduino Uno 5V to TM1637 4-digit display VCC; Arduino Uno GND to TM1637 4-digit display GND.

What parts do I need for this Arduino project?

An Arduino Uno and a TM1637 4-digit display.

Can I simulate this Arduino project online for free?

Yes. The BitForBytes Embedded Lab runs this exact circuit and Arduino C++ code in your browser for free, with no install and no hardware. The sketch is compiled with the real Arduino toolchain and runs on an emulated ATmega328P.

What does the code do?

A TM1637 counter on two wires, with the start, stop and acknowledge bits written by hand.