Portable E-Ink Weather Monitor

#include <Arduino.h>
#include <Wire.h>
#include <SPI.h>
#include <Adafruit_BME280.h>
#include <GxEPD2_BW.h>
#include <GxEPD2_290_T5.h>
#include <Fonts/FreeMonoBold9pt7b.h>
#include <Fonts/FreeMonoBold12pt7b.h>


// Forward declarations
void drawHeader();
void drawReadings();
void fullScreenDraw();
void partialReadingsDraw();

constexpr int BME_SDA_PIN = 21;
constexpr int BME_SCL_PIN = 22;
constexpr int EPD_SCK_PIN = 18;
constexpr int EPD_MOSI_PIN = 23;
constexpr int EPD_CS_PIN = 4;
constexpr int EPD_DC_PIN = 27;
constexpr int EPD_RST_PIN = 26;
constexpr int EPD_BUSY_PIN = 25;
constexpr uint32_t UPDATE_INTERVAL_MS = 300000UL;

Adafruit_BME280 bme;
GxEPD2_BW<GxEPD2_290_T5, GxEPD2_290_T5::HEIGHT> display(
  GxEPD2_290_T5(EPD_CS_PIN, EPD_DC_PIN, EPD_RST_PIN, EPD_BUSY_PIN)
);

bool sensorReady = false;
uint32_t lastUpdateMs = 0;

void drawHeader()
{
  display.setTextColor(GxEPD_BLACK);
  display.setFont(&FreeMonoBold12pt7b);
  display.setCursor(8, 20);
  display.print("ENVIRONMENT");
  display.drawLine(6, 28, display.width() - 6, 28, GxEPD_BLACK);
}

void drawReadings()
{
  display.fillRect(0, 34, display.width(), display.height() - 34, GxEPD_WHITE);
  display.setTextColor(GxEPD_BLACK);

  if (!sensorReady)
  {
    display.setFont(&FreeMonoBold9pt7b);
    display.setCursor(8, 62);
    display.print("BME280 NOT FOUND");
    display.setCursor(8, 86);
    display.print("Check SDA/SCL wiring");
    return;
  }

  const float temperatureC = bme.readTemperature();
  const float humidity = bme.readHumidity();
  const float pressureHpa = bme.readPressure() / 100.0F;

  display.setFont(&FreeMonoBold9pt7b);
  display.setCursor(8, 54);
  display.printf("Temp: %5.1f C", temperatureC);
  display.setCursor(8, 80);
  display.printf("Hum : %5.1f %%", humidity);
  display.setCursor(8, 106);
  display.printf("Press: %4.0f hPa", pressureHpa);
}

void fullScreenDraw()
{
  display.setFullWindow();
  display.firstPage();
  do
  {
    display.fillScreen(GxEPD_WHITE);
    drawHeader();
    drawReadings();
  }
  while (display.nextPage());
}

void partialReadingsDraw()
{
  display.setPartialWindow(0, 32, display.width(), display.height() - 32);
  display.firstPage();
  do
  {
    drawReadings();
  }
  while (display.nextPage());
}

void setup()
{
  Serial.begin(115200);
  Wire.begin(BME_SDA_PIN, BME_SCL_PIN);
  sensorReady = bme.begin(0x77);

  SPI.begin(EPD_SCK_PIN, -1, EPD_MOSI_PIN, EPD_CS_PIN);
  display.init(115200, true, 2, false);
  display.setRotation(1);
  fullScreenDraw();
  lastUpdateMs = millis();
}

void loop()
{
  const uint32_t now = millis();
  if (now - lastUpdateMs >= UPDATE_INTERVAL_MS)
  {
    sensorReady = bme.begin(0x77);
    partialReadingsDraw();
    lastUpdateMs = now;
  }
}