smart dc power

#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <Adafruit_ADS1X15.h>
#include <Adafruit_INA219.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

constexpr int SD_CS_PIN = 4;
constexpr int ACK_BUTTON_PIN = 32;
constexpr int LOG_BUTTON_PIN = 33;
constexpr int BUZZER_PIN = 27;
constexpr int NORMAL_LED_PIN = 13;
constexpr int WARNING_LED_PIN = 14;
constexpr int ALARM_LED_PIN = 26;

constexpr float NTC_BETA = 3950.0f;
constexpr float NTC_R0 = 10000.0f;
constexpr float NTC_T0_K = 298.15f;
constexpr float CAUTION_TEMP_C = 50.0f;
constexpr float ALARM_TEMP_C = 60.0f;
constexpr float CAUTION_CURRENT_A = 1.20f;
constexpr float ALARM_CURRENT_A = 1.40f;
constexpr unsigned long SAMPLE_PERIOD_MS = 1000UL;
constexpr unsigned long LOG_PERIOD_MS = 10000UL;

enum Status { NORMAL, CAUTION, ALARM, SENSOR_FAULT };

Adafruit_ADS1115 ads;
Adafruit_INA219 ina219;
Adafruit_SSD1306 display(128, 64, &Wire, -1);

bool sdReady = false;
bool alarmAcknowledged = false;
bool lastAckPressed = false;
bool lastLogPressed = false;
unsigned long lastSampleMs = 0;
unsigned long lastLogMs = 0;
unsigned long previousSampleMs = 0;
float busVoltageV = 0.0f;
float currentA = 0.0f;
float temperatureC = NAN;
float energyWh = 0.0f;
Status status = SENSOR_FAULT;

float readTemperatureC() {
  int16_t raw = ads.readADC_SingleEnded(1);
  float nodeVolts = ads.computeVolts(raw);
  if (nodeVolts <= 0.01f || nodeVolts >= 3.29f) return NAN;
  float ntcOhms = NTC_R0 * nodeVolts / (3.3f - nodeVolts);
  float inverseKelvin = (1.0f / NTC_T0_K) + log(ntcOhms / NTC_R0) / NTC_BETA;
  return (1.0f / inverseKelvin) - 273.15f;
}

Status determineStatus() {
  if (isnan(temperatureC)) return SENSOR_FAULT;
  float magnitudeA = fabsf(currentA);
  if (temperatureC >= ALARM_TEMP_C || magnitudeA >= ALARM_CURRENT_A) return ALARM;
  if (temperatureC >= CAUTION_TEMP_C || magnitudeA >= CAUTION_CURRENT_A) return CAUTION;
  return NORMAL;
}

const char *statusText(Status value) {
  switch (value) {
    case NORMAL: return "NORMAL";
    case CAUTION: return "CAUTION";
    case ALARM: return "ALARM";
    default: return "CHECK TEMP SENSOR";
  }
}

void setIndicators(Status value) {
  digitalWrite(NORMAL_LED_PIN, value == NORMAL ? HIGH : LOW);
  digitalWrite(WARNING_LED_PIN, value == CAUTION ? HIGH : LOW);
  digitalWrite(ALARM_LED_PIN, (value == ALARM || value == SENSOR_FAULT) ? HIGH : LOW);
}

void drawScreen() {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("DC SAFETY MONITOR");
  display.print("V: "); display.print(busVoltageV, 2); display.println(" V");
  display.print("I: "); display.print(currentA, 3); display.println(" A");
  display.print("P: "); display.print(busVoltageV * currentA, 2); display.println(" W");
  display.print("T: ");
  if (isnan(temperatureC)) display.println("--.- C");
  else { display.print(temperatureC, 1); display.println(" C"); }
  display.print("Used: "); display.print(energyWh, 3); display.println(" Wh");
  display.print("State: "); display.println(statusText(status));
  display.display();
}

void appendLog(const char *reason) {
  if (!sdReady) return;
  File log = SD.open("/dc_monitor.csv", FILE_APPEND);
  if (!log) return;
  log.print(millis()); log.print(',');
  log.print(busVoltageV, 3); log.print(',');
  log.print(currentA, 4); log.print(',');
  log.print(busVoltageV * currentA, 3); log.print(',');
  if (isnan(temperatureC)) log.print("nan");
  else log.print(temperatureC, 2);
  log.print(',');
  log.print(energyWh, 4); log.print(',');
  log.print(statusText(status)); log.print(',');
  log.println(reason);
  log.close();
}

void takeSample() {
  unsigned long now = millis();
  busVoltageV = ina219.getBusVoltage_V();
  currentA = ina219.getCurrent_mA() / 1000.0f;
  temperatureC = readTemperatureC();
  if (previousSampleMs != 0) {
    float elapsedHours = (now - previousSampleMs) / 3600000.0f;
    float positivePowerW = max(0.0f, busVoltageV * currentA);
    energyWh += positivePowerW * elapsedHours;
  }
  previousSampleMs = now;
  Status oldStatus = status;
  status = determineStatus();
  if (status == NORMAL || status != oldStatus) alarmAcknowledged = false;
  setIndicators(status);
  drawScreen();
  if ((status == ALARM || status == SENSOR_FAULT) && !alarmAcknowledged) tone(BUZZER_PIN, 2400, 180);
  else if (status == CAUTION && !alarmAcknowledged) tone(BUZZER_PIN, 1200, 80);
}

void setup() {
  pinMode(ACK_BUTTON_PIN, INPUT_PULLUP);
  pinMode(LOG_BUTTON_PIN, INPUT_PULLUP);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(NORMAL_LED_PIN, OUTPUT);
  pinMode(WARNING_LED_PIN, OUTPUT);
  pinMode(ALARM_LED_PIN, OUTPUT);
  setIndicators(SENSOR_FAULT);
  Wire.begin(21, 22);
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  ads.begin(0x48);
  ads.setGain(GAIN_ONE);
  ina219.begin();
  SPI.begin(18, 19, 23, SD_CS_PIN);
  sdReady = SD.begin(SD_CS_PIN, SPI);
  if (sdReady && !SD.exists("/dc_monitor.csv")) {
    File log = SD.open("/dc_monitor.csv", FILE_WRITE);
    if (log) {
      log.println("milliseconds,volts,amps,watts,temp_c,energy_wh,state,reason");
      log.close();
    }
  }
  takeSample();
  lastSampleMs = millis();
  lastLogMs = millis();
}

void loop() {
  bool ackPressed = digitalRead(ACK_BUTTON_PIN) == LOW;
  bool logPressed = digitalRead(LOG_BUTTON_PIN) == LOW;
  if (ackPressed && !lastAckPressed) {
    alarmAcknowledged = true;
    noTone(BUZZER_PIN);
  }
  if (logPressed && !lastLogPressed) appendLog("manual");
  lastAckPressed = ackPressed;
  lastLogPressed = logPressed;
  unsigned long now = millis();
  if (now - lastSampleMs >= SAMPLE_PERIOD_MS) {
    lastSampleMs = now;
    takeSample();
  }
  if (sdReady && now - lastLogMs >= LOG_PERIOD_MS) {
    lastLogMs = now;
    appendLog("periodic");
  }
}