Do I need to buy hardware for this tutorial?

No. Everything runs in the browser: Circuitly simulates the board, the components and the code. Real hardware is optional if you want to rebuild the circuit afterwards.

Which components are used?

Arduino UNO board, Push button, SSD1306 OLED display (I²C), MPU6050 IMU, BMP280 pressure/temperature sensor, DS3231 real-time clock. They are already available in the simulator library.

How long does it take?

About 50 minutes, expert level, in 4 guided steps.

What should I know before starting?

The previous tutorial in the series, “Project: obstacle-avoiding robot”, is enough preparation. No software install is required.

Is the code provided and checked?

Yes: a starter sketch is provided, and the simulator checks your wiring and your code automatically at every step.

All tutorials

6 · Full projects

Project: smartwatch

Expert50 min

Goal

Show time, steps and temperature on the OLED, with button navigation.

Why it matters

Combines clock, IMU, environmental sensor and UI: a complete product.

What you need

Arduino UNO board
Push button
SSD1306 OLED display (I²C)
MPU6050 IMU
BMP280 pressure/temperature sensor
DS3231 real-time clock

Nothing to buy: every component below is simulated in the browser.

Steps

01Shared I²C bus: OLED 0x3C, DS3231 0x68, MPU6050 0x69, BMP280 0x76.
02Count steps by detecting acceleration peaks.
03A button cycles through the screens (time / steps / weather).
04Refresh the screen only when data changes.

Starter sketch

// BMP280 temperature + pressure and DS3231 clock, straight over Wire.
#include <Wire.h>

const uint8_t BMP = 0x76;
const uint8_t RTC = 0x68;

uint16_t calT1; int16_t calT2; uint16_t calP1;

uint8_t readReg8(uint8_t addr, uint8_t reg) {
  Wire.beginTransmission(addr);
  Wire.write(reg);
  Wire.endTransmission(false);
  Wire.requestFrom(addr, (uint8_t)1);
  return Wire.read();
}

uint16_t readLE16(uint8_t reg) {
  Wire.beginTransmission(BMP);
  Wire.write(reg);
  Wire.endTransmission(false);
  Wire.requestFrom(BMP, (uint8_t)2);
  uint8_t lo = Wire.read();
  uint8_t hi = Wire.read();
  return (uint16_t)((hi << 8) | lo);
}

long read20(uint8_t reg) {
  Wire.beginTransmission(BMP);
  Wire.write(reg);
  Wire.endTransmission(false);
  Wire.requestFrom(BMP, (uint8_t)3);
  long msb = Wire.read();
  long lsb = Wire.read();
  long xlsb = Wire.read();
  return ((msb << 16) | (lsb << 8) | xlsb) >> 4;
}

uint8_t fromBcd(uint8_t v) { return (v >> 4) * 10 + (v & 0x0F); }

void setup() {
  Serial.begin(9600);
  Wire.begin();
  calT1 = readLE16(0x88);
  calT2 = (int16_t)readLE16(0x8A);
  calP1 = readLE16(0x8E);
  Serial.print("BMP280 id 0x");
  Serial.println(readReg8(BMP, 0xD0), HEX);
}

void loop() {
  long adcT = read20(0xFA);
  long adcP = read20(0xF7);
  float tFine = ((adcT / 16384.0) - (calT1 / 1024.0)) * calT2;
  float tempC = tFine / 5120.0;
  float pa = (1048576.0 - adcP) * 6250.0 / calP1;

  Serial.print("T ");
  Serial.print(tempC);
  Serial.print(" C   P ");
  Serial.print(pa / 100.0);
  Serial.println(" hPa");

  uint8_t h = fromBcd(readReg8(RTC, 0x02));
  uint8_t m = fromBcd(readReg8(RTC, 0x01));
  uint8_t s = fromBcd(readReg8(RTC, 0x00));
  Serial.print("RTC ");
  Serial.print(h); Serial.print(":");
  Serial.print(m); Serial.print(":");
  Serial.println(s);

  delay(1000);
}

This tutorial runs inside the Circuitly simulator: your wiring and your code are checked automatically at every step.

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Frequently asked questions

Do I need to buy hardware for this tutorial?: No. Everything runs in the browser: Circuitly simulates the board, the components and the code. Real hardware is optional if you want to rebuild the circuit afterwards.
Which components are used?: Arduino UNO board, Push button, SSD1306 OLED display (I²C), MPU6050 IMU, BMP280 pressure/temperature sensor, DS3231 real-time clock. They are already available in the simulator library.
How long does it take?: About 50 minutes, expert level, in 4 guided steps.
What should I know before starting?: The previous tutorial in the series, “Project: obstacle-avoiding robot”, is enough preparation. No software install is required.
Is the code provided and checked?: Yes: a starter sketch is provided, and the simulator checks your wiring and your code automatically at every step.

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