How to Build Your Own Arduino UNO Board

Building your very own Arduino UNO board can be a rewarding experience, allowing you to understand the inner workings of this popular microcontroller platform. This guide will walk you through the process step-by-step, explaining not only how to assemble the physical components but also how to upload the necessary firmware.

Ingredients for Your DIY Arduino UNO Board

Microchip’s ATmega328P – the heart of the board USB to UART converter Voltage Regulator (LM7805 or AMS1117-5V for a 5V regulated power supply) Passive Components: Resistors, Capacitors, Crystals A spare Arduino UNO Board Patience and a soldering iron Arduino IDE Software

Power Supply

First, you need to set up a 5V power supply for your Arduino UNO. The board can draw power from a USB port (which already supplies 5V) or from a DC jack. If you choose to use the DC jack for battery power (e.g., a 12V lead acid battery or a 9V alkaline battery), you’ll need a 5V voltage regulator, such as LM7805 or AMS1117-5V. Additionally, a MOSFET switch is necessary to switch between these power sources, protecting the USB power source from potential damage.

Building the Power Supply Circuit

To build the power supply circuit, you can use a 5V dual power supply, which is essential for a stable operation of the board. Here’s a basic setup:

USB power: Connect the VCC pin of the Arduino to 5V and the GND pin to ground. DC jack power: Use a 5V voltage regulator to convert the DC power to 5V. Connect the output of the voltage regulator to VCC and the GND pin to ground. MOSFET switch: Use a MOSFET like the P-Channel MOSFET to switch between the two power sources. Connect the gate of the MOSFET to the DTR pin of the serial converter for reset control. Capacitors: Parallel capacitors are used to filter out power supply noise.

ATmega328P Wiring

The ATmega328P requires a stable 5V supply to function properly. According to its datasheet, connect the VCC and AVCC pins to the 5V output of the power supply, and connect the GND pins to ground. However, for Arduino UNO to perform optimally, you need to add a clock source. This can be either an internal RC oscillation circuit or an external crystal.

Using a Crystal

For precise timing, it’s recommended to use a crystal. Connect the crystal between the TOSC1 (PB6) and TOSC2 (PB7) pins of the ATmega328P, and connect 22pF ceramic capacitors between each crystal leg and the pins.

Using an RC Oscillator

If you want a simpler solution, you can use an internal RC oscillator. However, this method is less accurate and can vary with temperature changes. The factory default setting for the ATmega328P is 8MHz internal RC.

Uploading the Bootloader

The bootloader is a crucial piece of firmware that allows you to upload new sketches to the Arduino via the USB port. To upload the bootloader, you’ll need to program the ATmega328P using another Arduino UNO board as an ISP (In-System Programmer).

Wiring the USB to UART Converter

Some options for converting USB to UART signals are mentioned, such as using an ATmega16U2, FTDI232, or CH40G. These USB to UART converters are necessary because ATmega328P does not have built-in USB support. Connect the D and D- pins of the USB to UART converter to the RX and TX pins of the ATmega328P, respectively.

Ensure that the Reset pin of the ATmega328P is connected to the DTR pin of the USB to UART converter via a 100nF capacitor to ensure that the MCU resets during programming.

Final Testing

To test if your DIY Arduino UNO board is working correctly, follow these steps:

Follow the bootloader upload tutorial. Use a CH340G USB to UART converter to test the circuit.

Once everything is set up, your board should be ready for programming via the Arduino IDE. Good luck!

Enjoy building and coding with your DIY Arduino UNO board!