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Firmware Getting Started — SELV Spa-Light Switch Controller
MCU
Microchip PIC16F18855, 3.3 V logic, internal oscillator recommended. Enable WDT, BOR, CRC/checksum on configuration data, and fail-safe relay OFF defaults.
Pin Map
Table
| Net | MCU Pin | Direction | Firmware Function |
|---|---|---|---|
| BTN_ONOFF | RB0 | Input | Debounced manual ON/OFF button |
| BTN_MODE | RB1 | Input | Debounced local program/mode fallback |
| OPTICAL_PROG_IN | RB2 | Input | Active-low 40 kHz demodulated IR command input |
| MAINS_PRESENT | RB3 | Input | Isolated mains-present status |
| RELAY_FB | RB4 | Input | Optional auxiliary relay contact feedback |
| RELAY_SET | RC0 | Output | Pulse latching relay SET coil driver |
| RELAY_RESET | RC1 | Output | Pulse latching relay RESET coil driver |
| LED_POWER | RC2 | Output/PWM | PWM dimmed power/status LED sink |
| I2C_SCL | RC3 | I2C | Ambient light sensor clock |
| I2C_SDA | RC4 | I2C | Ambient light sensor data |
| LED_STATUS | RA1 | Output/PWM | Fault/status LED sink |
| TEMP_SENSE | RA0 | ADC | 10k NTC temperature divider |
| ICSPCLK | RB6 | Programming | PICkit ICSP clock |
| ICSPDAT | RB7 | Programming | PICkit ICSP data |
| MCLR_VPP | RE3/MCLR/VPP | Reset/programming | Reset and programming voltage |
Required Firmware Behaviors
- Default state after reset, brownout, watchdog, overtemperature, invalid config, or invalid optical command: relay OFF.
- Enter programming mode only after valid optical wake/preamble plus 2-second valid optical pulse or structured command frame.
- Ignore incomplete/invalid optical commands and apply timeout.
- Relay remains OFF during programming and for 60 seconds after programming ends.
- Store configuration in EEPROM/internal flash with CRC/checksum.
- On mains loss, disable LEDs/relay drive, timestamp outage if possible, and enter low-power hold-up mode.
MCU
Pin Map
Required Firmware Behaviors
