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--- pm:prj2026:florin.stancu:dinu.merceanu [2026/05/07 20:40]
dinu.merceanu
+++ pm:prj2026:florin.stancu:dinu.merceanu [2026/05/13 22:48] (current)
dinu.merceanu [Introduction]
@@ Line 3: / Line 3: @@
 <note tip>
-A two-player reaction time game inspired by the Romanian TV show "Am întrebat 100 de Români". Three red LEDs light up one by one, then turn off simultaneously after a random delay — this is the start signal. The first player to press their button wins: their blue LED lights up and an OLED display shows the winner and their reaction time in milliseconds.
+A two-player reaction time game inspired by the Romanian TV show "Ce spun romanii" and by the start lights of Formula 1. Three red LEDs light up one by one, then turn off simultaneously after a random delay — this is the start signal. The first player to press their button wins: their blue LED lights up and an OLED display shows the winner and their reaction time in milliseconds.
 The goal of the project is to create a simple yet engaging interactive game that tests the reflexes of two players. The idea started from TV shows where contestants must react as fast as possible to a visual signal.
 The project is useful as a practical demonstration of hardware interrupts, timers and I2C communication on an AVR microcontroller, while also being an accessible example of an interactive embedded system.
@@ Line 28: / Line 28: @@
 ===== Hardware Design =====
-<note tip>
+==== Bill of Materials ====
-Aici puneţi tot ce ţine de hardware design:
-  * listă de piese
+^ Component ^ Quantity ^ Details ^
-  * scheme electrice (se pot lua şi de pe Internet şi din datasheet-uri, e.g. http://www.captain.at/electronic-atmega16-mmc-schematic.png)
+| ATmega328p XMINI | 1 | Main development board |
-  * diagrame de semnal
+| OLED display | 1 | 0.96" SSD1306, I2C, 128x64px |
-  * rezultatele simulării
+| LED red | 3 | 5mm, countdown signal |
-</note>
+| LED blue | 2 | 5mm, winner indicator |
+| Resistor 220Ω | 5 | Current limiting for LEDs |
+| Push button | 2 | 12x12mm tactile with round cap |
+| Breadboard | 1 | 830 points |
+| Jumper wires | 19 | Male-to-male|
+==== Pin Connections ====
+^ Pin ^ Component ^ Role ^
+| PB0 | LED1 red + 220Ω | Countdown LED 1 |
+| PB1 | LED2 red + 220Ω | Countdown LED 2 |
+| PB2 | LED3 red + 220Ω | Countdown LED 3 |
+| PB3 | LED4 blue + 220Ω | Winner indicator Player 1 |
+| PB4 | LED5 blue + 220Ω | Winner indicator Player 2 |
+| PB7 | SW0 (on-board) | Start / restart game |
+| PD2 | Button Player 1 | External interrupt INT0 |
+| PD3 | Button Player 2 | External interrupt INT1 |
+| PC4 (SDA) | OLED display | I2C data |
+| PC5 (SCL) | OLED display | I2C clock |
+| VCC | OLED display | 3.3V - 5V power |
+| GND | All components | Common ground |
+==== Hardware Schematic Diagram ====
+{{ :pm:prj2026:florin.stancu:hardwareschematicdiagram.png?800 |}}
+==== Signal diagram ====
+The game follows a fixed sequence of states:
+  - **IDLE** — waiting for start button (PB7)
+  - **COUNTDOWN** — LED1, LED2, LED3 light up one by one, 1 second apart. Player button presses during this phase trigger a false start (INT0/INT1).
+  - **RANDOM DELAY** — all 3 LEDs remain on for a random interval between 1 and 3 seconds.
+  - **GO** — all LEDs turn off simultaneously. Timer1 starts measuring reaction time.
+  - **RESULT** — first player to press wins. Winner LED lights up, OLED displays both reaction times. If a false start occurred, the offending player is disqualified.
 ===== Software Design =====
+==== Development Environment ====
-<note tip>
+The firmware was developed using **PlatformIO** integrated into **Visual Studio Code**,
-Descrierea codului aplicaţiei (firmware):
+targeting the ATmega328P with the Arduino framework (used only as a build system —
-  * mediu de dezvoltare (if any) (e.g. AVR Studio, CodeVisionAVR)
+all peripheral control is done via direct AVR register access, without any Arduino
-  * librării şi surse 3rd-party (e.g. Procyon AVRlib)
+library functions).
-  * algoritmi şi structuri pe care plănuiţi să le implementaţi
-  * (etapa 3) surse şi funcţii implementate
+Upload is done via the **xplainedmini** protocol using avrdude, over USB.
-</note>
+==== Third-party Libraries and Sources ====
+No external libraries were used. All drivers were implemented from scratch using
+AVR-libc headers only:
+  * ''<avr/io.h>'' — register definitions
+  * ''<avr/interrupt.h>'' — ISR macro and sei()/cli()
+  * ''<util/delay.h>'' — _delay_ms() for debouncing
+The SSD1306 OLED driver, TWI/I2C driver, USART driver, and timer modules were
+written entirely by hand, inspired by the laboratory implementations provided
+during the PM course.
+==== File Structure ====
+^ File ^ Role ^
+| ''src/main.cpp'' | Game logic, state machine, ISR definitions |
+| ''src/uptime.cpp'' | Timer2 CTC — 1ms system tick counter |
+| ''src/timers.cpp'' | Timer1 CTC — reaction time measurement |
+| ''src/twi.cpp'' | I2C/TWI driver using AVR hardware TWI module |
+| ''src/ssd1306.cpp'' | SSD1306 OLED driver with 5x7 bitmap font |
+| ''src/usart.cpp'' | UART driver for serial debug output |
+| ''include/uptime.h'' | uptime_ms() declaration |
+| ''include/timers.h'' | Timer1_init/start/stop/get_ms declarations |
+| ''include/twi.h'' | TWI function declarations and frequency config |
+| ''include/ssd1306.h'' | SSD1306 function declarations |
+| ''include/usart.h'' | USART function declarations |
+==== Algorithms and Data Structures ====
+**Game state machine**
+The game runs as a sequential state machine inside the main loop:
+  - ''IDLE'' — display shows "READY", waiting for SW0 (PB7) press
+  - ''COUNTDOWN'' — LED1, LED2, LED3 light up one by one at 1s intervals using non-blocking timing via uptime_ms(). External interrupts INT0/INT1 are active during this phase to detect false starts.
+  - ''RANDOM DELAY'' — all 3 LEDs remain on for a random interval (1–3 seconds), generated via rand() seeded with uptime_ms()
+  - ''GO'' — LEDs turn off, Timer1 starts counting reaction time
+  - ''RESULT'' — first player to press wins. If a false start was detected, the offending player is disqualified. Results are shown on OLED and serial.
+**Non-blocking timing**
+All delays during the countdown and random delay phases use the pattern:
+<code c>
+uint32_t t = uptime_ms();
+while ((uptime_ms() - t) < 1000 && !false_start_p1 && !false_start_p2);
+</code>
+This allows the main loop to remain responsive to false start interrupts even
+while waiting.
+**False start detection**
+External interrupts INT0 (PD2) and INT1 (PD3) are configured for falling edge
+detection. ISRs set volatile flags only if ''game_started == 0'':
+<code c>
+ISR(INT0_vect) { if (!game_started) false_start_p1 = 1; }
+ISR(INT1_vect) { if (!game_started) false_start_p2 = 1; }
+</code>
+**Reaction time measurement**
+Timer1 is initialized in CTC mode at 16MHz with prescaler 8, generating an
+interrupt every 1ms (OCR1A = 1999). A volatile counter ''reaction_ticks''
+increments in the ISR. Timer1_start() resets and enables it; Timer1_get_ms()
+reads the counter atomically using cli()/sei().
+**I2C communication**
+The TWI hardware module is configured for 100kHz SCL frequency. The SSD1306
+driver sends initialization commands on startup, then writes character bitmaps
+page by page using twi_start/twi_write/twi_stop sequences.
+**OLED font rendering**
+Characters are stored as a 5x7 bitmap font in Flash memory (PROGMEM) for
+ASCII characters (space through Z). Each character is 5 bytes wide plus
+byte spacing. ssd1306_print_str() renders a string at a specified page row (0–7).
 ===== Rezultate Obţinute =====