Introduction

Arduino reduced early electronics design and prototyping obstacles. Eliminating C programming and datasheet/application note reading democratizes access. High-quality Arduino software libraries improve usability and capabilities.

Fifteen years ago, professional engineers had to design a WiFi-connected data transmitter. Modules and online courses simplify it. After your Arduino prototype works, compress it to fit a sleek container and remove extraneous components to save money—Arduino PCB design.

This tutorial covers two MCUs. The cheap ATTiny85/45/25 works with the Arduino UNO R3's ATMega328P.

Essential Connections

When creating your personalized Arduino board design diagram, establish connections between the subsequent pins and incorporate the specified elements beneath.

Power

Connect the power source to all VCC and AVCC pins (not found in ATTiny). Both MCUs run from 2.7V to 5.5V. A loud power supply may require AVCC to be filtered with an inductor and capacitor (LC filter calculator).

Connect all GND pins to the circuit ground.

Bypass Capacitors

Place a 100nF/50V/X7R ceramic capacitor near each (A)VCC pin. Parallel a 1uF or 10uF ceramic capacitor if the power source has a low-frequency ripple.

Programming interface

SPI and /RESET will deliver code to MCUs.

Connect SCK, MOSI, MISO, or RESET to a connection.

The /RESET pins need a VCC-connected 10kohm pull-up resistor.

Crystal

Connect a 16MHz crystal and 100Kohm feedback resistor to pins XTAL1 and XTAL2 of the ATMega328P. Calculate crystal capacitors. Use CSTNE16M0V530000R0, a crystal with capacitors.

Layout Considerations for Custom Arduino Board Design

1. Correct connector pinout and placement bypass capacitors near VCC pins save time and prevent problems.

2. Use a 2.54mm pin header for direct programming.

3. Connect the nets to the programmer.

Programming

Arduinos have two MCUs, Arduino R3 and Arduino UNO R3. The smaller MCU is a programmer that converts USB protocol data into serial and supports the Serial() function, while the larger MCU runs your code.

We'll need an extra board to replace this component, as we didn't include it. We'll use the AVR USBasp programmer.

Arduino IDE Configuration ATMega328P

Select these Tools menu options:

1.    Arduino-configured ATMega328P.

2.    Select a port.

3.    Select Upload Using Programmer in Sketch.

Before uploading code to a new MCU without flashing, click Burn Bootloader.

Arduino IDE Configuration ATTiny85/45/25

Install SpenceKonde's ATTinyCore Library to program ATTinys. Following library installation, do these:

1.    On Tools, choose ATTiny setup, Arduino.

2.    Choose a port.

3.    Select Upload Using Programmer in Sketch.

Tips for ATTiny

Memory

Excellent ATTiny microcontrollers have limited flash memory and RAM. Before choosing an MCU, modify your Arduino UNO sketch for the ATTiny library. Verify and compile the code.

Insufficient space causes code to fail to compile without errors. Optimize the code or find an MCU with more memory.

Serial

The 85/45/25 ATTinys lack serial peripherals. However, you can use SoftwareSerial like the Arduino UNO.

Simplicity

Step-by-step code debugging is a major drawback of the Arduino IDE. The Arduino IDE's serial monitor, flags, and variable displays can solve this. This method lacks a serial PC connection.

Conclusion

Creating a personalized Arduino board is incredibly simple. This brief guide aims to help you swiftly turn your projects into commercial prototypes.

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