ATMega328P uC Expansion Board

PCB Circuits (click to enlarge) Circuits and Info

Eagle CAD: 1. Expansion Schematic


Resources Allocated


Eagle CAD: 2. Expansion PCB




(Bill of Materials)


ATMega328P Main Board Top


ATMega328P Main Board Bottom


ATMega328P Expansion Board

Update 2020-07-19

I've redesigned the base board and expansion board. RX and TX drivers have been added, and the GPIO ports have been reassigned to free up the interrupt ports D2 and D3. I'll update the pix shortly.


The uC Expansion Board

The expansion board fits on top of the base ATMega328P uC board.

All digital, analog and power connections are passed from the base board female headers to the expansion board.



The expansion board has the following features:
Feature Product ID Digital/Analog Pins  I2C Address or Comments

Banggood 1.3" OLED (128x64)






Chinese 1.3" OLED (128x64)











I2C (A5 SCL, A4 SDA)

Geekcreit 4-pin I2C 128 x 64 monocolour OLED display

 - I2C address 0x3C or 0x3D

 - No Reset pin needed

 - Uses SH1106 display driver

 - pinout: GND, VCC, SCL, SDA


Chinese 4-pin I2C 128 x 64 monocolour OLED display

 - I2C address 0x3C or 0x3D

 - No Reset pin needed

 - Uses SSD1306 display driver

 - pinout: GND, VCC, SCL, SDA

Adafruit BME280 sensor 2652 I2C  (A5 SCL, A4 SDA) Temp, humidity, BP sensor. I2C address 0x77 or 0x76.
Adafruit RGB LED


D3, D4, D5 Diffused tri-colour 5mm, 20mA average current draw for all 3 colours, Brightness: Red 500mcd, green 600mcd, blue 300 mcd.
Sparkfun Buzzer circuit 7950 D6 Complete driver circuit for the piezo buzzer/speaker. Can be used to play tones, melodies, etc.
Tactile momentary switch 1119 D7, D8, D9 3 switches are available, perhaps for menu item selection?
LDR: light dependent resistor SEN-09088 A0 An LDR is a resistor that changes its resistive value (in ohms depending on much light is shining on its face.
Banggood PIR motion sensor 1011714 A1 Motion sensor with a range of about 6 feet (2m).
Adafruit Micro SD Card module 254 SPI (D10, D11, D12, D13) and A1 Due to lack of space on the expansion board, this module can be attached to bottom of the ATmega328P uC board

uC Expansion Bd. Sketches =>



Tags: Arduino-type Microcontroller, ATMega328P