ATmega88PA Sensor Interface Board

This project is a compact microcontroller development board based on the ATmega88PA, equipped with an MPU-6050 accelerometer/gyroscope and USB interface. It is designed for embedded systems development, particularly in motion-sensing or robotics applications.

Features

• Microcontroller: ATmega88PA (TQFP32)
• IMU Sensor: MPU-6050 (3-axis gyroscope + 3-axis accelerometer)
• USB Interface: CH340C USB-to-Serial converter
• Onboard Voltage Regulation: 5V to 3.3V via AP2112K-3.3
• USB Power and Data via Micro-USB
• External Programming Header (ISP)
• I2C and UART breakout pins
• Reset and User Button
• LED Indicators: Power and status/debug
• Crystal Oscillator: 8 MHz external crystal
• Compact, breadboard-friendly form factor

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Schematic Overview

• Power Supply:
  • Micro-USB supplies +5V.
  • LDO (AP2112K-3.3) regulates down to +3.3V for MPU-6050 and I/O.
• Microcontroller (U2): ATmega88PA is the central controller.
  • Interfaces: I2C (SCL/SDA), UART (TX/RX), and SPI (MISO/MOSI/SCK)
  • Reset circuitry via pushbutton and capacitor.
• MPU-6050 (U4): Connected via I2C with 4.7kΩ pull-ups.
• USB to Serial (U3 - CH340C):
  • Used for serial communication and programming via UART.
• ISP Header (J1): For initial bootloader flashing or full firmware flashing.

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PCB Details

• 2-layer PCB with top and bottom copper planes.
• Carefully routed signal traces with decoupling capacitors close to ICs.
• Exposed pads for easy pin access to GPIOs.
• Mounting holes and labeled pin headers.
• Silkscreen labeling of pin functions for ease of use.
• 3D Render available for visualization and placement inspection.

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Pinout Summary

Pin	Function	Notes
PB0–PB7	GPIO / UART / SPI	Digital I/O and communication
PC0–PC5	GPIO / I2C	Includes SDA/SCL for MPU6050
PD0–PD7	GPIO / UART	TX/RX, user-defined GPIO
SW1	Reset Button	Pull-down with 10kΩ resistor
SW2	User Button	Connected to PB0
J1	ISP Header	MISO/MOSI/SCK/RESET

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Getting Started

1. Flashing Firmware

• Via ISP (J1): Use AVR ISP programmer.
• Via UART (CH340C): Use bootloader (if pre-installed).

2. Power Supply

• Plug in via Micro-USB.
• Onboard LDO provides 3.3V logic supply.

3. I2C Communication

• MPU-6050 is accessible at default I2C address 0x68.
• Ensure pull-ups (R3, R4 = 4.7kΩ) are present on SDA/SCL lines.

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Tools Used

• Schematic & PCB Design: KiCad EDA
• Microcontroller Programming: avrdude, Arduino as ISP, PlatformIO
• Firmware Development: C/C++ (AVR-GCC or Arduino IDE)

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License

Open-source hardware. You may use, modify, and distribute under the terms of the MIT license.