Srinivasa Says: a Pi-Memorization Memory Game

~Challenge your brain with the infinite decimals of π in this Simon-style electronic game.~

Named after the legendary mathematician Srinivasa Ramanujan, who had an uncanny intuition for infinite series and π, this project is a "Simon Says" style game with a mathematical twist. Instead of random colors, you must follow the actual sequence of Pi: 3.14159...

Unlike standard memory games that use random sequences, Srinivasa Says uses the constant nature of Pi to help you memorize its digits through musical notes. It’s a perfect project for Pi Day, combining bare-metal programming, custom PCB design, and 3D printing.

Video example!

To build this project, you will need:

Core Electronics:

1. Microcontroller: ATmega328P-PU (DIP-28 package).
2. Clock: 16 MHz Quartz Crystal + 2x 22pF capacitors.
3. Audio: Passive Piezo Buzzer.
4. Volume Control: 10k Trimmer (Potentiometer).
5. Visuals: 5mm LEDs (Red for error, Green for success) + 2N3904 NPN Transistors (drivers).

Power & Interface:

1. USB-C Connector (for 5V power).
2. Buttons: 10x Tactile switches (0-9 digits) + 3x control buttons.
3. PCB: Custom designed (Gerber files attached).

Software & Tools:

1. Microchip Studio (or Atmel Studio) for C programming.
2. AVRDUDE + USBASP Programmer.
3. BambuLab A1 mini (or any 3D printer) for the enclosure.

The heart of the system is a standalone ATmega328P.

Key Design Choices:

1. LED Drivers: Instead of connecting LEDs directly to the MCU, I used 2N3904 transistors. This ensures the MCU pins don't exceed their current rating and provides consistent brightness.
2. Volume Management: A 10k trimmer works as a variable resistor in series with the buzzer. I added a 37 Omega resistor to prevent short circuits when the volume is at maximum.
3. Decoupling: 100nF capacitors are placed close to the VCC and AVCC pins to filter high-frequency noise.

Check the electronic design here.

This project moves away from the Arduino IDE to use pure C (AVR-Libc). This allows for precise control over the hardware timers.

Tone Generation: We use Timer1 in CTC mode (Clear Timer on Compare Match). The frequency of each note is calculated using:

OCR1A=FCPU/(2⋅Prescaler⋅fnote​​​)−1

The Logic: The Pi sequence is stored in a constant array. The game compares the user's button press with the corresponding index in the pi_digits[] array.

Check the firmware source code here.

To make the project portable and "pro", I designed a custom PCB in EasyEDA.

Manufacturing:

1. The PCB was manufactured via JLCPCB.
2. The enclosure was modeled in Blender/Fusion 360 to fit the PCB perfectly.
3. 3D Printing: Printed in PETG-HF for durability. I also designed custom button caps to fit the long-neck tactile switches.

Check the mechanical design here.

Since we are not using an Arduino board, we need an external programmer.

1. Connect the USBASP to the ISP pins of the ATmega328P.
2. Set the Fuses (Low: 0x7F, High: 0xD9) to enable the 16MHz external crystal.
3. Upload the .hex file using AVRDUDE: avrdude -c usbasp -p m328p -U flash:w:srinivasa.hex:i

Check the compiled files here.

Power On: Toggle the rocker switch.

The Challenge: The device will play the first digit of Pi (3) with a specific tone.

Input: Press the "3" button.

Progression: If correct, you'll hear a success beep, and the sequence grows: 3, then 1, then 4...

Game Over: If you fail, the red LED lights up and a "Low-frequency" error tone sounds. Can you beat the world record?

Creating Srinivasa Says has been a journey through the intersection of mathematics, embedded systems, and industrial design. Moving away from standard development boards to a standalone ATmega328P allowed for a deeper understanding of AVR architecture and power management.

Key Takeaways:

1. Hardware vs. Software: Implementing volume control via a physical trimmer proved to be more efficient and "noise-free" than a software-based PWM approach.
2. Precision Matters: Using an external 16MHz crystal was essential to maintain the musical integrity of the notes, ensuring that "Pi" always sounds the same.
3. Customization: 3D printing custom button caps transformed a simple PCB into a professional-feeling handheld device.

This project is a tribute to Srinivasa Ramanujan and a reminder that even the most complex mathematical constants, like π, can be turned into a fun, tactile, and musical experience.

What's Next? For version 2.0, I plan to implement EEPROM storage to save high scores and develop a lot of other modalities, by just replacing the firmware.

P.S.: I've memorized more than 90 digits, how can you? :)

Video example!