Portable Battery Monitor

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_INA219.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define INA_SDA 21
#define INA_SCL 22
#define OLED_CLK 18
#define OLED_DIN 23
#define OLED_CS 27
#define OLED_DC 17
#define OLED_RES 16
#define PAGE_BUTTON 32
#define STATUS_BUTTON 33
#define GREEN_LED 25
#define RED_LED 26


// Hoisted type definitions
enum BuddyMood { HAPPY, SILLY, SLEEPY, SURPRISED };


// Forward declarations
bool pressed(uint8_t pin, unsigned long &lastPress);
void drawEye(int x, int y, bool closed, bool surprised);
void drawMouth(BuddyMood mood, int y);
void drawBuddy();
void drawStatus();
void updateMeter();

Adafruit_INA219 ina219;
Adafruit_SSD1306 display(128, 64, OLED_DIN, OLED_CLK, OLED_DC, OLED_RES, OLED_CS);


BuddyMood selectedMood = HAPPY;

float busVoltage = 0.0f;
float loadCurrent = 0.0f;
unsigned long lastMeterRead = 0;
unsigned long lastAnimation = 0;
unsigned long pagePressedAt = 0;
unsigned long statusPressedAt = 0;
bool blinkEyes = false;
bool showStatus = false;
bool sensorFound = false;

bool pressed(uint8_t pin, unsigned long &lastPress) {
  if (digitalRead(pin) == LOW && millis() - lastPress > 250) {
    lastPress = millis();
    return true;
  }
  return false;
}

void drawEye(int x, int y, bool closed, bool surprised) {
  if (closed) {
    display.drawLine(x - 10, y, x + 10, y, SSD1306_WHITE);
    return;
  }
  int height = surprised ? 20 : 16;
  display.fillRoundRect(x - 10, y - height / 2, 20, height, 7, SSD1306_WHITE);
  display.fillCircle(x, y, surprised ? 3 : 4, SSD1306_BLACK);
  if (!surprised) display.fillCircle(x + 1, y - 1, 1, SSD1306_WHITE);
}

void drawMouth(BuddyMood mood, int y) {
  if (mood == HAPPY) {
    display.drawCircle(64, y - 8, 13, SSD1306_WHITE);
    display.fillRect(49, y - 21, 30, 13, SSD1306_BLACK);
  } else if (mood == SILLY) {
    display.drawLine(51, y - 4, 60, y + 3, SSD1306_WHITE);
    display.drawLine(60, y + 3, 69, y - 3, SSD1306_WHITE);
    display.drawLine(69, y - 3, 78, y + 4, SSD1306_WHITE);
    display.fillRoundRect(59, y + 3, 10, 6, 2, SSD1306_WHITE);
  } else if (mood == SLEEPY) {
    display.drawLine(52, y, 76, y, SSD1306_WHITE);
  } else {
    display.drawCircle(64, y - 1, 7, SSD1306_WHITE);
  }
}

const char *moodName(BuddyMood mood) {
  switch (mood) {
    case HAPPY: return "HAPPY";
    case SILLY: return "SILLY";
    case SLEEPY: return "SLEEPY";
    default: return "WOW!";
  }
}

void drawBuddy() {
  bool lowPower = sensorFound && busVoltage < 4.75f;
  BuddyMood faceMood = lowPower ? SLEEPY : selectedMood;
  bool closed = blinkEyes || faceMood == SLEEPY;

  display.clearDisplay();
  display.drawRoundRect(1, 1, 126, 62, 7, SSD1306_WHITE);
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(8, 7);
  display.print("BUDDY: ");
  display.print(lowPower ? "NEEDS CHARGE" : moodName(faceMood));

  drawEye(42, 33, closed, faceMood == SURPRISED);
  drawEye(86, 33, closed, faceMood == SURPRISED);
  drawMouth(faceMood, 52);

  display.setCursor(10, 55);
  display.print("PAGE=mood  STATUS=meter");
  display.display();
}

void drawStatus() {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("BUDDY POWER METER");
  display.drawLine(0, 10, 127, 10, SSD1306_WHITE);

  if (!sensorFound) {
    display.setCursor(0, 22);
    display.println("INA219 not found.");
    display.println("Check SDA/SCL wiring.");
  } else {
    display.setTextSize(2);
    display.setCursor(0, 16);
    display.print(busVoltage, 2);
    display.println("V");
    display.setCursor(0, 38);
    display.print(loadCurrent, 0);
    display.println("mA");
    display.setTextSize(1);
    display.setCursor(88, 48);
    display.print(busVoltage * loadCurrent / 1000.0f, 2);
    display.print("W");
  }
  display.setTextSize(1);
  display.setCursor(0, 55);
  display.print("Press STATUS for Buddy");
  display.display();
}

void updateMeter() {
  if (!sensorFound || millis() - lastMeterRead < 500) return;
  lastMeterRead = millis();
  busVoltage = ina219.getBusVoltage_V();
  loadCurrent = ina219.getCurrent_mA();
  if (loadCurrent < 0) loadCurrent = 0;

  bool lowPower = busVoltage < 4.75f;
  digitalWrite(RED_LED, lowPower ? HIGH : LOW);
  digitalWrite(GREEN_LED, lowPower ? LOW : HIGH);
}

void setup() {
  pinMode(PAGE_BUTTON, INPUT_PULLUP);
  pinMode(STATUS_BUTTON, INPUT_PULLUP);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(RED_LED, LOW);

  Wire.begin(INA_SDA, INA_SCL);
  sensorFound = ina219.begin();

  if (!display.begin(SSD1306_SWITCHCAPVCC)) {
    while (true) { delay(100); }
  }
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(2);
  display.setCursor(18, 20);
  display.println("Hi! ^_^ ");
  display.display();
  delay(1200);
}

void loop() {
  updateMeter();

  if (pressed(PAGE_BUTTON, pagePressedAt)) {
    selectedMood = static_cast<BuddyMood>((selectedMood + 1) % 4);
    showStatus = false;
  }
  if (pressed(STATUS_BUTTON, statusPressedAt)) {
    showStatus = !showStatus;
  }

  if (millis() - lastAnimation > 180) {
    lastAnimation = millis();
    blinkEyes = !blinkEyes;
    if (showStatus) drawStatus();
    else drawBuddy();
  }
}