Arduino Nano from Scratch

📄 View Schematic PDF

Overview

This project describes a custom-designed microcontroller development board, similar to an Arduino Nano, based on the ATmega328P-M. The board integrates a stable 5V power supply, a USB-to-serial converter for programming and UART/SPI communication, and comprehensive pin headers for flexible interfacing.

Figure 1: Front view of the PCB

Figure 2: Back view of the PCB

Project Architecture

The project is structured hierarchically within KiCad, with the following key sub-schematics:

1. Root: The top-level schematic, connecting the main blocks.
2. Project Architecture: Defines the overall system architecture.
   • Pins: Exposes the digital and analog I/O pins.
   • Power Supply: Provides a regulated 5V supply.
   • USB Port: Handles USB communication and power.
   • Microcontroller: Contains the ATmega328P-M and its supporting circuitry.

PCB Layers

The PCB is meticulously designed with the following 4 layers to optimize signal integrity, power delivery networks (PDN), and component density, ensuring robust performance and manufacturability:

1. Layer Top (F.Cu - Front Copper):

   • Description: This is the primary component placement layer, primarily accommodating Surface Mount Devices (SMDs) and through-hole components. It's strategically utilized for critical high-speed signal routing, decoupling capacitor placement, and minimizing trace lengths for impedance control on sensitive lines.
   • 

2. 5V (In1.Cu - Inner Copper 1):

   • Description: A dedicated internal power plane for the +5V rail. This continuous copper plane ensures low-impedance power distribution, minimizing voltage ripple and providing a robust, stable current source across the entire board, critical for power integrity of digital logic.
   • 

3. GND (In2.Cu - Inner Copper 2):

   • Description: A comprehensive internal ground plane. This solid plane serves as a universal low-impedance return path for all signals, significantly reducing electromagnetic interference (EMI), enhancing electromagnetic compatibility (EMC), and providing effective shielding for sensitive traces.
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4. Layer Bottom (B.Cu - Bottom Copper):

   • Description: Utilized for completing signal routing, particularly for less sensitive signals or those requiring longer runs. This layer also accommodates additional SMD component placement and provides flexibility for thermal management via copper pours if needed.
   • 

Key Components

• U1: ATmega328P-M Microcontroller
• U2: LM1117-5.0 Voltage Regulator
• U3: FT232RL USB-to-Serial Converter
• J1: USB Mini-B connector
• J2, J4: Main I/O Headers
• J6, J7: ICSP Headers

Important Files

• Arduino Nano.kicad_pro: KiCad project file.
• Arduino Nano.kicad_sch: Top-level schematic.
• Microcontroller.kicad_sch, Pins.kicad_sch, Power Supply.kicad_sch, USB Port.kicad_sch: Hierarchical sub-schematic files.
• Arduino Nano.kicad_pcb: PCB layout file.
• Arduino Nano.kicad_dru: PCB design rules file.
• Arduino Nano.kicad_prl: Project-specific library settings.