Author: Goda Gutparakyte
Course: Introduction to Robotics at Vilnius University
Assignment: HW2
Last Updated: 2025-10-06
This project implements a reaction time tester using an Genuino Uno, two buttons, LEDs, a buzzer, and an LCD display.
Logic:
- Press the main button to start
- Wait for the green LED to turn on (also 'NOW!' on LCD screen) — then press as fast as possible
- The display shows your reaction time in milliseconds and whether your score made it to the top scores
- Best results socreboard is automatically in EEPROM
- To see top scores, press the menu button
- Connect all components according to the wiring table provided below
- Open the
.inofile in Arduino IDE - Select Board: Arduino Uno
- Select the correct COM port
- Click Upload
The system uses Timer1 (16-bit) to generate a 1 ms interrupt for managing non-blocking displays and implementing reaction time measurement.
Timer settings:
- CPU Clock: 16 MHz
- Prescaler: 64
- OCR1A: 249 → produces 1 ms tick rate
- Mode: CTC (Clear Timer on Compare Match)
- ISR:
ISR(TIMER1_COMPA_vect)incrementsms_ticks
| ISR | Trigger | Pin | Description |
|---|---|---|---|
button_ISR() |
CHANGE | 2 | Detects presses of the main play button |
menu_ISR() |
FALLING | 3 | Detects menu button press to show the scoreboard. |
TIMER1_COMPA_vect |
1 ms timer | — | Updates ms_ticks for all timing logic. |
Top scores are stored persistently in EEPROM to survive power cycles.
| Address | Size (bytes) | Description |
|---|---|---|
0–1 |
2 | Magic number (0x5254) |
2 |
1 | EEPROM version |
3 |
1 | Score count (number of scores) |
4–... |
... | Top scores list (n scores × 2 bytes each) |
Constants:
EMPTY_SCORE = 0xFFFF— unused score slotMAX_SCORES = 10— top 10 fastest reaction times (can be adjusted)
| Name | Quantity | Component |
|---|---|---|
| U1 | 1 | Arduino Uno R3 |
| D1 | 1 | Red LED |
| D2 | 1 | Green LED |
| R1, R2 | 2 | 220 Ω Resistor |
| S1, S2 | 2 | Pushbutton |
| R3, R4 | 2 | 1 kΩ Resistor |
| U2 | 1 | LCD 16x2 Display |
| PIEZO1 | 1 | Piezo Buzzer |