Mini Arcade With Arduino Nano R4 (duo Invaders)

The Arduino UNO R4 is a powerhouse, but it isn’t exactly pocket-friendly. The Arduino Nano R4 brings the same 32-bit muscle to the classic Nano footprint, runs happily at 5 V, and slots straight into older Nano projects. To show it off, I built a miniature arcade cabinet that plays a tiny space shooter called Duo Invaders.

Highlights

• 48 MHz Cortex-M4, 256 KB Flash, 32 KB SRAM, 8 KB EEPROM
  
• 5 V operation for drop-in compatibility with legacy Nano projects
  
• 128×64 SPI OLED, three buttons (Left/Right/Fire), two piezo buzzers
  
• Compact 3D-printed enclosure with a removable side panel

Why Nano R4 for this?

• Drop-in power-up: 5 V pins mean older Nano shields and sensors just work.
  
• Headroom for graphics: 32 KB SRAM lets us keep an 8 KB framebuffer for smooth sprites.
  
• Tidy mixed-signal: 14-bit ADC, 12-bit DAC, on-chip op-amp for future upgrades.
  
• Production-friendly: Flat underside and castellations make it easy to embed on a PCB.

Wiring at a glance

OLED (SPI):
SCK → D13, MOSI → D11, CS → D10, DC → D9, RST → D8

Buttons (active-low):
LEFT → D2, RIGHT → D3, FIRE → D4 (enable internal pull-ups)

Audio:
BGM piezo → D5, SFX piezo → D6 (other pins work—just match the code)

Power:
USB-C on the Nano R4. The right-angle USB-C keeps the cable clear of the back panel.

Enclosure & print notes

The case is two pieces: the main body and a removable side panel so you can wire and test before sealing it up.

• Filament: PLA or PETG
  
• Layer height: 0.2 mm
  
• Infill: 15–20%
  
• Tolerances: leave clearance for the OLED bezel, button caps, and the USB-C adapter

How the graphics stay smooth

SSD1306-style OLEDs store 8 vertical pixels per byte, which makes overlapping sprites fiddly. The Nano R4’s SRAM means we can keep a full 128×64 byte buffer (~8 KB), draw sprites there, then compress to the 1 KB page format and push over SPI. It’s a memory-for-speed trade that keeps animation crisp and leaves time for input, logic, and audio.

Pseudo frame routine:

drawSpritesToFramebuffer();
packFramebufferToPages();
oledTransferPages();

Code structure (what lives where)

• gpu.h / gpu.cpp — framebuffer + packer (128×64 bytes → page format)
  
• player.h — player sprite & missile behaviour
  
• invaders.h — enemy sprites + animation frames
  
• audio.h — two simple tone routines (BGM + fire SFX)
  
• level.h — the state machine: movement, firing, collisions, scoring, lives
  
• main.ino — pin setup, GPU init, and runLevel() loop

Gameplay loop (simplified)

1. Read inputs (debounced)
   
2. Move player / enemies (time-based)
   
3. Update missiles and check collisions
   
4. Draw to framebuffer, pack, send to OLED
   
5. Play/overlay tones
   
6. If all enemies cleared → start next level

Build steps

1. Prep the stripboard. Socket the Nano R4; keep SPI runs short.
   
2. Wire the OLED. Connect SPI lines + DC/CS/RST to the chosen pins.
   
3. Add buttons. Three inputs to D2/D3/D4; other side to GND. Enable pull-ups.
   
4. Add buzzers. D5 and D6 to piezos; other legs to GND.
   
5. Right-angle USB-C. Test cable fit with the shell closed.
   
6. Flash the sketch. Arduino IDE 2.x; select Nano R4; upload and test.
   
7. Final assembly. Fix the OLED, route the wiring, close the side panel.

Testing checklist

• OLED initialises and shows the title screen
  
• Left/Right move the player; Fire launches a missile
  
• Enemies step, drop, and wrap correctly
  
• Background tone plays; fire SFX overlays cleanly
  
• USB-C cable exits neatly; enclosure shuts flush

Troubleshooting

• Blank display: check CS/DC/RST pins and reset timing; reduce SPI clock if needed.
  
• Button jitter: ensure pull-ups are enabled; add a simple debounce check.
  
• Audio missing: confirm pins aren’t reused and piezos are wired to GND.
  
• Tearing/flicker: shorter SPI leads, solid ground, and pack/transfer once per frame.

Make it your own

• Add a start menu and difficulty levels in level.h
  
• Use the DAC/op-amp for richer audio
  
• External I²C score display via the Qwiic/Quick connector
  
• Scale to a bigger display—just update the buffer and packer

Where to buy

• Arduino Nano R4 with headers (ABX00143) — Electromaker shop
  https://www.electromaker.io/shop/product/arduino-nano-r4-with-headers