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3. Output Devices

I have some grove interface device, such as :rgb led, button,oled display,buzzer etc. I use ESP32Uno and Seed's Base Shield Grove extension board to connect them.

3.1 Output Device - Servo​

3.1.1 Servo Motor​

The 180° Servo Motor (also known as Standard Servo or Position Servo) is a rotary actuator that rotates to a specific angular position between 0° and 180° based on a PWM control signal. It is widely used in robotics, RC vehicles, and automated mechanical systems requiring precise angular positioning.

3.1.2 Working Principle -Pulse Width Modulation (PWM) Control​

The servo motor determines its target angular position by receiving a PWM signal from a controller .

While the standard signal period is typically 20ms (50Hz), it is the Pulse Width (the duration of the "High" voltage) that dictates the specific angle of the output shaft:

  • 0.5ms to 1.0ms: Corresponds to the 0° position.

  • 1.5ms: Corresponds to the 90° (neutral/middle) position.

  • 2.0ms to 2.5ms: Corresponds to the 180° position.

3.1.3 I connect Servo (3pin) to my PCB 3p pin header.​

Wire ColorPinFunction
BlackGGround (GND / -)
RedVPower (VCC / +)
YellowS (GPIO18)Signal (SIG / Data)

3.1.3 I write block code in MicroBlocks for quick testing :​

I want to make the servo to rotate when I press the button.

3.1.4 Here is the testing of servo :​

3.2 Output Device - OLED Display​

3.2.1 OLED Display​

The 0.96-inch OLED Display is a compact, high-contrast monochrome screen widely used in embedded electronics and DIY projects. It features 128×64 pixels resolution and communicates via I2C or SPI interfaces, making it ideal for microcontrollers like Arduino and ESP32.

3.2.2 Working Principle​

The 0.96" OLED operates on the principle of Electroluminescence. Unlike LCDs that require a backlight, OLED pixels emit their own light when an electric current passes through the organic layers.

  • Self-Emission: Each of the 128 × 64 pixels acts as an independent light source. This allows for "True Black" because pixels in dark areas are simply turned off.

  • Controller (SSD1306): This chip acts as the "brain," translating I2C/SPI commands into electrical signals that light up specific coordinates on the 128 × 64 grid.

  • Efficiency: Since only the active pixels consume power, it is highly efficient for displaying text and simple UI elements in battery-powered devices.

3.2.3 Here is my PCB pin connection with 0.96-inch OLED:​

OLED PinESP32 PinFunction
GNDGNDGround
VCC5VPower Supply
SCKGPIO22I2C Clock Line (SCL)
SDAGPIO21I2C Data Line (SDA)

3.2.4 I write block code in MicroBlocks for quick testing :​

I want to show information on the OLED display - "Welcome FabAcademy 2026 Dolphin assignment"

3.2.5 Here is the testing of OLED Display :​

3.3 Output Device - 4Digital Display​

3.3.1 4-digital display​

The TM1637 4-Digit Display is a compact and cost-effective LED display module featuring four 7-segment digits with a built-in colon for clock functionality. It integrates the TM1637 driver chip, which handles all scanning and decoding tasks, requiring only two GPIO pins (CLK and DIO) for communication via a proprietary serial protocol.

3.3.2 Working Principle​

The TM1637 module communicates with the host controller via a 2-wire serial interface (CLK, DIO). Its core operating principles are as follows:

  • Auto-Scanning: The integrated dynamic scanning circuit sequentially drives each digit internally, maintaining stable 4-digit display without requiring continuous CPU refresh.

  • Pin Efficiency: Only 2 GPIO pins control up to 32 LED segments (4 digits × 8 segments), significantly reducing hardware resource usage compared to direct drive methods.

  • Internal Display RAM: Data sent to the chip is stored in built-in registers until the next update, minimizing communication overhead and bus traffic.

  • Programmable Brightness: 8-level brightness control via software commands, allowing adaptation to varying ambient lighting conditions.

3.3.3 Here is my PCB pin connection with 4-digital display:​

4-Digital DisplayESP32 PinFunction
GNDGNDGround
VCC5V / 3.3VPower Supply
DIOGPIO19Data I/O (Serial Data)
CLKGPIO18Clock Signal (Serial Clock)

3.3.4 I write block code in MicroBlocks for quick testing :​

I want to show from 1 to 10 in 4-digital display.

3.3.5 Here is the testing of 4-digital display :​

3.4 Output Device - Active Buzzer Module

3.4.1 Active Buzzer Module​

The Active Buzzer Module is a simple, self-contained audio output device that generates a fixed-tone sound when powered. Unlike passive buzzers, it includes a built-in oscillator circuit, requiring only a DC voltage (HIGH signal) to produce sound—no PWM or external frequency generation needed.

3.4.2 Working Principle​

The Active Buzzer Module is designed for simplicity: DC voltage in → fixed sound out. Unlike a passive buzzer, it does not require a fluctuating signal (PWM) to produce tone.

Core Components Inside the Module

  • Electromagnetic Buzzer Element (diaphragm + coil)

  • Built-in Oscillator Circuit (transistor, resistor, capacitor — often potted in black epoxy)

  • Driver Transistor (on the module board, for current amplification)

  • Current-limiting Resistor (protects the control pin)

  • Three pins (usually: VCC, GND, I/O)

FeatureActive BuzzerPassive Buzzer
Needs PWM / variable frequency?❌ No✅ Yes
Needs DC voltage (HIGH signal)?✅ Yes❌ No (needs AC/square wave)
Built-in oscillator?✅ Yes❌ No

3.4.3 Connect Active Buzzer Module to my PCB 3p pin header.​

Buzzer PinESP32 PinFunction
GNDGNDGround
VCC5V / 3.3VPower Supply
I/O / SGPIO19Signal Input (HIGH = ON, LOW = OFF)

3.4.4 Coding​

I write block code in MicroBlocks for quick testing :

I want to buzzer to play a song "happy birthday".

3.4.5 Testing​

Here is the testing of buzzer :

3.5. Resource​