I2CRelay/examples/Slave/Slave.ino

#include <Wire.h>
#include <EEPROM.h>

#define EEPROM_SIZE        64
#define EEPROM_ADDR_LOC    0         // EEPROM location for I2C address
#define EEPROM_NAME_LOC    1         // EEPROM location for device name
#define DEVICE_NAME_LEN    24
#define DEFAULT_I2C_ADDR   0x08      // Default I2C address

char deviceName[DEVICE_NAME_LEN] = "Relay";
uint8_t i2cAddress = DEFAULT_I2C_ADDR;

// I2C command codes
enum Command : uint8_t {
  CMD_SET_ADDR = 0x01,
  CMD_SET_NAME = 0x02,
};

// --- RELAY FEATURE ADDITIONS ---
const int relayPins[8] = {0, 1, 2, 3, 4, 5, 6, 7}; // GPIOs 0-7
uint8_t relayStates[8] = {0};                      // 0=OFF, 1=ON
unsigned long relayTimers[8] = {0};                // millis() when to turn off, 0 = no timer

enum RelayCommand : uint8_t {
  CMD_RELAY_SET       = 0x10, // [relay#][0|1]   (relay# = 1..8)
  CMD_RELAY_ALL       = 0x11, // [0|1]
  CMD_RELAY_TIMER     = 0x12, // [relay#][ms_L][ms_H][ms_U][ms_T]
  CMD_RELAY_ALL_TIMER = 0x13  // [ms_L][ms_H][ms_U][ms_T]
};

// *** INVERTED RELAY LOGIC ***
// User relay numbers: 1–8. Array indices: 0–7.
void setRelay(uint8_t relayNum, uint8_t state) {
  if (relayNum >= 1 && relayNum <= 8) {
    uint8_t idx = relayNum - 1;
    relayStates[idx] = (state == 1 ? 1 : 0);
    // Inverted logic: LOW = ON, HIGH = OFF
    digitalWrite(relayPins[idx], relayStates[idx] ? LOW : HIGH);
  }
}

void setAllRelays(uint8_t state) {
  for (uint8_t i = 1; i <= 8; i++) setRelay(i, state);
}
// --- END RELAY FEATURE ADDITIONS ---

void storeAddressToEEPROM(uint8_t addr) {
  EEPROM.write(EEPROM_ADDR_LOC, addr);
  EEPROM.commit();
}

uint8_t readAddressFromEEPROM() {
  uint8_t addr = EEPROM.read(EEPROM_ADDR_LOC);
  if (addr == 0xFF || addr == 0x00) {
    addr = DEFAULT_I2C_ADDR;
    storeAddressToEEPROM(addr);
  }
  return addr;
}

void storeNameToEEPROM(const char* name) {
  for (int i = 0; i < DEVICE_NAME_LEN; i++) {
    EEPROM.write(EEPROM_NAME_LOC + i, name[i]);
    if (name[i] == '\0') break;
  }
  EEPROM.commit();
}

void readNameFromEEPROM(char* name) {
  for (int i = 0; i < DEVICE_NAME_LEN; i++) {
    name[i] = EEPROM.read(EEPROM_NAME_LOC + i);
    if (name[i] == '\0') break;
  }
  name[DEVICE_NAME_LEN - 1] = '\0';
}

// Handle data received from master
void onReceive(int len) {
  if (len < 1) return;
  uint8_t cmd = Wire.read();
  switch (cmd) {
    case CMD_SET_ADDR:
      if (Wire.available()) {
        uint8_t newAddr = Wire.read();
        if (newAddr > 0x00 && newAddr < 0x78) {
          storeAddressToEEPROM(newAddr);
          ESP.restart();
        }
      }
      break;
    case CMD_SET_NAME: {
      int i = 0;
      while (Wire.available() && i < DEVICE_NAME_LEN - 1) {
        deviceName[i++] = Wire.read();
      }
      deviceName[i] = '\0';
      storeNameToEEPROM(deviceName);
      break;
    }
    // --- RELAY FEATURE ADDITIONS ---
    case CMD_RELAY_SET:
      if (Wire.available() >= 2) {
        uint8_t relayNum = Wire.read(); // Now 1..8
        uint8_t state = Wire.read();    // 0|1
        setRelay(relayNum, state);
        if (relayNum >= 1 && relayNum <= 8) relayTimers[relayNum-1] = 0;
      }
      break;
    case CMD_RELAY_ALL:
      if (Wire.available() >= 1) {
        uint8_t state = Wire.read(); // 0|1
        setAllRelays(state);
        for (int i = 0; i < 8; i++) relayTimers[i] = 0;
      }
      break;
    case CMD_RELAY_TIMER:
      if (Wire.available() >= 5) {
        uint8_t relayNum = Wire.read(); // 1..8
        uint32_t ms = Wire.read();
        ms |= ((uint32_t)Wire.read()) << 8;
        ms |= ((uint32_t)Wire.read()) << 16;
        ms |= ((uint32_t)Wire.read()) << 24;
        setRelay(relayNum, 1);
        if (relayNum >= 1 && relayNum <= 8)
          relayTimers[relayNum-1] = millis() + ms;
      }
      break;
    case CMD_RELAY_ALL_TIMER:
      if (Wire.available() >= 4) {
        uint32_t ms = Wire.read();
        ms |= ((uint32_t)Wire.read()) << 8;
        ms |= ((uint32_t)Wire.read()) << 16;
        ms |= ((uint32_t)Wire.read()) << 24;
        setAllRelays(1);
        unsigned long offTime = millis() + ms;
        for (int i = 0; i < 8; i++) relayTimers[i] = offTime;
      }
      break;
    // --- END RELAY FEATURE ADDITIONS ---
    default:
      break;
  }
}

// Handle data requested by master
void onRequest() {
  String response = String(i2cAddress, HEX) + ",GENERIC," + deviceName;
  Wire.write((const uint8_t*)response.c_str(), response.length());
}

void setup() {
  Serial.begin(115200);
  EEPROM.begin(EEPROM_SIZE);

  i2cAddress = readAddressFromEEPROM();
  readNameFromEEPROM(deviceName);

  Wire.begin(i2cAddress);
  Wire.onReceive(onReceive);
  Wire.onRequest(onRequest);

  for (int i = 0; i < 8; i++) {
    pinMode(relayPins[i], OUTPUT);
    digitalWrite(relayPins[i], HIGH); // Inverted logic: HIGH = OFF at start
  }

  Serial.print("I2C Slave started at address 0x");
  Serial.println(i2cAddress, HEX);
  Serial.print("Device name: ");
  Serial.println(deviceName);
}

void loop() {
  unsigned long now = millis();
  for (int i = 0; i < 8; i++) {
    if (relayTimers[i] && now >= relayTimers[i]) {
      setRelay(i+1, 0); // Use relay number 1..8
      relayTimers[i] = 0;
    }
  }
}