Arduino Tutorial

Arduino Uno R4 Minima

Arduino Uno R4 takes your familiar Arduino Uno to the next level while keeping the same form factor in order to be able to use the same shields. It utilises a 32 bit 48MHz ARM Cortex M4 of RA4M1 series from the manufacturer called Renesas(R7FA4M1AB3CFM).

The Arduino Uno R4 has two versions

  1. Arduino Uno R4 Minima
  2. Arduino Uno R4 WiFi
In this discussion we will only cover Arduino Uno R4 Minima
Arduino Uno R4 Minima Pinout
Arduino Uno R4 Minima Pinout
DC Input: 

Takes the input from DC source to power this device. Allows input voltage 6~24V via barrel jack input.

Buck Converter:

It regulates the higher input voltage to lower output voltage. In this case it regulates the input voltage (provided via barrel jack or Vin) to 5V in order to power the micro-controller in order to provide output signals and read input signals.


USB C can be used to power the micro-controller as well as upload the program/firmware to the micro-controller.

Reset Switch:

Just as the name mentions it resets the micro-controller by turning off and on the power to the EN pin of the micro-controller.

I2C, or Inter-Integrated Circuit:
  • Facilitates serial communication among multiple devices with SDA (data) and SCL (clock) wires.
  •  Utilizes a master-slave architecture, featuring unique addressing, start/stop conditions, and acknowledged data transfer for efficient inter-integrated circuit communication.
UART or Universal Asynchronous Receiver/Transmitter:
  •  Enables point-to-point communication between two devices via serial data transmission.
  • Transmits data sequentially, bit by bit, using transmit (TX) and receive (RX) wires.
  • SPI (Serial Peripheral Interface) is a synchronous communication protocol.
  • It enables high-speed data transfer between micro-controllers and peripheral devices.
  • SPI operates with a master-slave architecture.
  •  It supports full-duplex transmission.
  •  Communication occurs over multiple wires, including a clock line (SCK) and separate data lines for transmission(MOSI) and reception(MISO).
  •  Pins that are used for SPI Communication: 13(SCK), 12(MISO), 11(MOSI), 10(CS). 
SWD or Serial Wire Debug : 
  • Two-pin protocol for debugging and programming ARM-based micro-controllers.
  • Uses SWDIO for data transfer and SWCLK for clock synchronization.
  • Simpler and more efficient alternative to JTAG with fewer pins required.
ICSP or In-Circuit Serial Programming :
  • Six-pin interface used for programming micro-controllers.
  • Includes MISO, MOSI, SCK, RESET, VCC, and GND pins.
  • Allows programming and debugging directly on the micro-controller without removing it from the circuit.
Digital I/O Pins:
  • Pins 0-13: General-purpose digital input/output pins.
    • Pin 0 (RX): UART receive pin.
    • Pin 1 (TX): UART transmit pin.
  • Pins 2-3: Can be used for external interrupts.
  • Pins 4-5: Can be used for CAN bus where pin 4 is CAN TX and pin 5 is CAN RX.
  • Pins 3, 5, 6, 9, 10, 11: Provide PWM (Pulse Width Modulation) output.
  • Pin 13: Connected to the onboard LED.
  • Pin A0-A5: Can also be used as digital I/O pins in addition to analog inputs.
  • SPI Pins: Pins 10 – 14 can be used for SPI communication
Analog Pins :
  • Analog Input: Read analog voltage values (0-5V) and convert them to a 14-bit digital value .
  • Digital I/O: Can also be used as general-purpose digital input/output pins.
  • A0 can be used as 12-bit  Digital to Analog Converter.
  • Opamp I/O(A1, A2 ,A3): A1(IN+), A2(IN-) can be used as input to internal op-amp and A3 is used output from internal op-amp.
  •  I2C Pins (A4, A5): Used for I2C communication, with A4 as SDA and A5 as SCL.
Power Pins:
  • VIN: Input voltage to the Arduino board when using an external power source (6-24V recommended).
  • 5V: Regulated 5V output from the onboard voltage regulator; can power external components.
  • 3.3V: Regulated 3.3V output for low-voltage components.
  • GND: Ground pins (multiple available) for establishing a common ground reference.
Special Pins:
  • Analog Reference (AREF): Used to set an external reference voltage (0 to 5V) for the analog-to-digital converter (ADC). This allows for more accurate and stable analog readings when using the analogReference(EXTERNAL) function in  sketches.
  • I/O Voltage Reference (IOREF): Sets the operating voltage for input/output operations on the micro-controller, usually 5V. Shields adjust to this voltage for compatibility with the board’s level.
  • RESET: It is used to reset the micro-controller. 
  • BOOT: This pin is used to switch the micro-controller in between program mode and run/execute mode.
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