MCU:        PIC16F886
Frequency:  20 MHz (HS crystal)
Voltage:    5V
Flash:      8 KB
RAM:        368 bytes
EEPROM:     256 bytes

┌─────────────────────────────────────────┐
│              main.c                     │  ← Application Logic
│  • Initialization                       │
│  • ISR (Timer0/Timer1)                  │
│  • Main Loop (scheduler-driven)         │
└───────────────┬─────────────────────────┘
                │
    ┌───────────┴───────────┬─────────────┬──────────────┐
    ▼                       ▼             ▼              ▼
┌─────────┐         ┌──────────────┐  ┌──────────┐  ┌────────────┐
│ sensor/ │         │  actuador/   │  │protocol/ │  │    hal/    │
│         │         │              │  │          │  │            │
│ • temp  │         │  • led       │  │• uart    │  │• adc       │
│ • hum   │         │  • fan       │  │• sched   │  │• i2c       │
│ • noise │         │              │  │          │  │• spi       │
│ • lux   │         │              │  │          │  │• pwm       │
│ • co2   │         │              │  │          │  │• uart      │
│         │         │              │  │          │  │• eeprom    │
└────┬────┘         └──────┬───────┘  └────┬─────┘  └─────┬──────┘
     │                     │               │               │
     │                     │               │               │
     └─────────────────────┴───────────────┴───────────────┘
                                  │
                           ┌──────┴──────┐
                           │    lib/     │  ← Official Libraries
                           │             │
                           │ • i2c-v2    │  (Read-only)
                           │ • spi-v1    │
                           └─────────────┘

SMA-LAMP/
├── main.c                  # Application entry point and main loop
├── README.md              # This file - project overview
├── REGISTERS_MAP.md       # PIC16F886 register reference
│
├── lib/                   # Official vendor libraries (read-only)
│   ├── README.md         # Library documentation
│   ├── i2c-v2.c/h        # Hardware I2C driver
│   └── spi-master-v1.c/h # Bit-bang SPI driver
│
├── hal/                   # Hardware Abstraction Layer
│   ├── README.md         # HAL architecture and API reference
│   ├── hal_adc.c/h       # ADC peripheral (3 channels, 10-bit)
│   ├── hal_uart.c/h      # UART communication (9600 baud)
│   ├── hal_i2c.c/h       # I2C master (100 kHz)
│   ├── hal_spi.c/h       # SPI bit-bang implementation
│   ├── hal_pwm.c/h       # PWM generation (20 kHz)
│   └── hal_eeprom.c/h    # EEPROM read/write
│
├── sensor/                # Sensor driver implementations
│   ├── README.md         # Sensor specifications and usage
│   ├── sensor_temp.c/h   # LM35 temperature sensor (ADC)
│   ├── sensor_hum.c/h    # HIH4000 humidity sensor (ADC)
│   ├── sensor_noise.c/h  # Microphone noise level (ADC)
│   ├── sensor_lux.c/h    # VEML7700 light sensor (I2C)
│   └── sensor_co2.c/h    # iAQ-Core CO₂ sensor (I2C)
│
├── actuador/              # Actuator driver implementations
│   ├── README.md         # Actuator specifications and usage
│   ├── actuator_led.c/h  # SK9822 RGB LED strip (SPI)
│   └── actuator_fan.c/h  # PWM fan control
│
├── protocol/              # Communication and timing
│   ├── README.md         # Protocol specification
│   ├── protocol_uart.c/h # UART command protocol with CRC-8
│   └── scheduler.c/h     # Time-based event scheduler
│
└── test/                  # Individual component tests
    ├── README.md         # Testing documentation and procedures
    ├── test_fan.c        # Fan PWM ramp test
    ├── test_led.c        # LED color cycling test
    ├── test_command.c    # UART command reception test
    ├── test_co2.c        # CO₂ sensor I2C test
    ├── test_lux.c        # Light sensor I2C test
    ├── test_temperature.c # Temperature sensor ADC test
    ├── test_noise.c      # Noise sensor ADC test
    ├── test_humidity.c   # Humidity sensor ADC test
    └── test_eeprom.c     # EEPROM read/write test

Every 1 second:
    └─→ [AA 04 00 {cat} 00 00]          CMD_NOISE
    
Every 5 seconds:
    ├─→ [AA 04 06 {temp} 00 00]         CMD_TEMP
    ├─→ [AA 05 03 {hh} {hl} 00 00]      CMD_HUM
    ├─→ [AA 05 01 {lh} {ll} 00 00]      CMD_LUX
    └─→ [AA 05 02 {ch} {cl} 00 00]      CMD_CO2

Asynchronous (any time):
    ├─→ [AA 04 04 {speed} 00 00]              CMD_FAN
    └─→ [AA 07 05 {r} {g} {b} {br} 00 00]     CMD_LEDS

AA 04 06 19 00 00
│  │  │  │  └─ CRC
│  │  │  └──── Data: 25 (0x19)
│  │  └─────── Command: TEMP (0x06)
│  └────────── Length: 4
└───────────── Header: 0xAA

AA 07 05 FF 00 00 1F 00 00
│  │  │  │  │  │  │  └─ CRC
│  │  │  │  │  │  └──── Brightness: 31
│  │  │  │  │  └─────── Blue: 0
│  │  │  │  └──────────Green: 0
│  │  │  └───────────── Red: 255
│  │  └──────────────── Command: LEDS (0x05)
│  └─────────────────── Length: 7
└────────────────────── Header: 0xAA

Fosc/4 = 20MHz / 4 = 5 MHz
Period = 0.2 µs
Prescaler 1:256 → tick every 51.2 µs
10ms / 51.2µs = 195.3 ticks
Preload = 256 - 195 = 61

OPTION_REG = 0b10000111  // nRBPU=1 (PORTB pull-ups OFF), PSA=0, PS=111 (1:256), T0CS=0 (Fosc/4)
TMR0 += 61               // Compensated reload

Fosc/4 = 5 MHz
Prescaler 1:8 → tick every 1.6 µs
Overflow = 65536 × 1.6µs = 104.8576 ms

T1CON = 0b00110001      // TMR1ON=1, TMR1CS=0 (Fosc/4), T1CKPS=11 (1:8), TMR1GE=0 (always count)

1. Power-On Reset → PWRTE waits 72ms
2. main() starts
3. init_pins_min()          Configure TRIS registers
4. init_timers()            Start Timer0, Timer1, enable GIE
5. scheduler_init()         Reset tick counters
6. protocol_init(9600)      Initialize UART
7. Peripheral Init (once):
   ├─ adc_init()
   ├─ hal_i2c_init()
   ├─ spi_init()
   └─ pwm_init()
8. Sensor Init:
   ├─ temp_init()           (No-op)
   ├─ hum_init()            (No-op)
   ├─ noise_init()          (No-op)
   ├─ lux_init()            (No-op)
   └─ co2_init()            Reset warmup counter
9. Actuator Init:
   ├─ led_init()            Set default white color
   └─ fan_init()            Set speed to 0%
10. Restore from EEPROM:
    ├─ Read addresses 0x00-0x04
    ├─ Validate (check for 0xFF = empty)
    └─ Apply configuration
11. Diagnostic Test:
    ├─ Send CMD_NOISE = 0
    └─ Send CMD_TEMP = 25°C
12. Enter main loop

while(1) {
    // Event 1: Noise report (every 1s)
    if(scheduler_noise_ready()) {
        protocol_send(CMD_NOISE, {noise_max_cat}, 1);
        noise_max_cat = NOISE_LOW;  // Reset window
    }
    
    // Event 2: Environmental sensors (every 5s)
    if(scheduler_env_ready()) {
        save_actuators_state();     // Persist to EEPROM
        co2_update_warmup();         // Increment warmup counter
        
        temp = temp_read_degC();
        hum = hum_read_percent();
        lux = lux_read();
        co2 = co2_read_ppm();        // Returns 0xFFFF if not ready
        
        protocol_send(CMD_TEMP, ...);
        protocol_send(CMD_HUM, ...);
        protocol_send(CMD_LUX, ...);
        protocol_send(CMD_CO2, ...);
    }
    
    // Event 3: Command reception (asynchronous)
    if(protocol_receive(&cmd, buf, &len)) {
        switch(cmd) {
            case CMD_FAN:
                current_fan_speed = buf[0];
                fan_set_speed(current_fan_speed);
                break;
            case CMD_LEDS:
                current_led_r = buf[0];
                current_led_g = buf[1];
                current_led_b = buf[2];
                current_led_brightness = buf[3];
                led_set_color(...);
                break;
        }
        
        // Activity indicator: flash green LED
        led_set_color(0, 255, 0, 10);
        __delay_ms(50);
        led_set_color(current_led_r, current_led_g, current_led_b, current_led_brightness);
    }
}

AA 04 00 00 00 00    → CMD_NOISE = 0
AA 04 06 19 00 00    → CMD_TEMP = 25°C