How to Build a Morning Thermal Printer with ESP32

// ESP32 Daily Briefing Printer
// Connects to Wi-Fi, fetches weather from Open-Meteo, fetches Google Calendar events,
// then prints a daily briefing with date, weather, appointments, and to-do lines.

#include <Arduino.h>
#include <WiFi.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>
#include "Adafruit_Thermal.h"
#include <time.h>
#include <esp_sleep.h>

// ─── USER CONFIGURATION ──────────────────────────────────────────────────────
#define WIFI_SSID        "YOUR_WIFI_SSID"
#define WIFI_PASSWORD    "YOUR_WIFI_PASSWORD"

// Google Calendar API
// 1. Create a project at console.cloud.google.com
// 2. Enable the Calendar API
// 3. Create an API key (restricted to Calendar API)
// 4. Share your calendar publicly (view only) or use OAuth (beyond MVP scope)
#define GOOGLE_API_KEY   "YOUR_GOOGLE_API_KEY"
#define CALENDAR_ID      "YOUR_CALENDAR_ID"   // e.g. "primary" or full email

// Open-Meteo — Amsterdam coordinates (no API key required)
#define WEATHER_LAT      "52.3676"
#define WEATHER_LON      "4.9041"

// NTP
#define NTP_SERVER       "pool.ntp.org"
#define TZ_OFFSET_SEC    3600   // UTC+1 (Amsterdam CET); adjust for DST manually or use TZ string
#define TZ_DST_SEC       3600   // additional DST offset (1 h in summer)

// Number of to-do lines to print
#define TODO_LINES       5
// ─────────────────────────────────────────────────────────────────────────────

// Pin definitions
#define PRINTER_RX_PIN   4    // ESP32 TX → Printer RX
#define PRINTER_TX_PIN   5    // Printer TX → ESP32 RX (optional / status)

// Printer baud rate
#define PRINTER_BAUD     9600

// Hoisted type definitions
struct WeatherData {
    float tempMin;
    float tempMax;
    float precipitation;
    int   weatherCode;
    bool  valid;
};

struct CalEvent {
    char summary[64];
    char timeStr[32];   // "HH:MM" or "All day"
};

HardwareSerial printerSerial(2);
Adafruit_Thermal printer(&printerSerial);

// ─── WMO weather code → short description ────────────────────────────────────
const char* weatherDescription(int code) {
    if (code == 0)              return "Clear sky";
    if (code == 1)              return "Mainly clear";
    if (code == 2)              return "Partly cloudy";
    if (code == 3)              return "Overcast";
    if (code >= 45 && code <= 48) return "Foggy";
    if (code >= 51 && code <= 55) return "Drizzle";
    if (code >= 61 && code <= 65) return "Rain";
    if (code >= 71 && code <= 75) return "Snow";
    if (code >= 80 && code <= 82) return "Rain showers";
    if (code >= 95 && code <= 99) return "Thunderstorm";
    return "Unknown";
}

bool connectWifi() {
    Serial.printf("Connecting to %s", WIFI_SSID);
    WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
    int attempts = 0;
    while (WiFi.status() != WL_CONNECTED && attempts < 30) {
        delay(500);
        Serial.print(".");
        attempts++;
    }
    if (WiFi.status() == WL_CONNECTED) {
        Serial.println(" connected!");
        return true;
    }
    Serial.println(" FAILED.");
    return false;
}

void syncTime() {
    configTime(TZ_OFFSET_SEC, TZ_DST_SEC, NTP_SERVER);
    Serial.print("Syncing time");
    struct tm ti;
    int attempts = 0;
    while (!getLocalTime(&ti) && attempts < 20) {
        delay(500);
        Serial.print(".");
        attempts++;
    }
    Serial.println(getLocalTime(&ti) ? " done." : " FAILED.");
}

WeatherData fetchWeather() {
    WeatherData wd = {0, 0, 0, 0, false};
    if (WiFi.status() != WL_CONNECTED) return wd;

    HTTPClient http;
    String url = "https://api.open-meteo.com/v1/forecast"
                 "?latitude=" WEATHER_LAT
                 "&longitude=" WEATHER_LON
                 "&daily=temperature_2m_max,temperature_2m_min,precipitation_sum,weathercode"
                 "&timezone=Europe%2FAmsterdam"
                 "&forecast_days=1";

    http.begin(url);
    int httpCode = http.GET();
    if (httpCode != 200) {
        Serial.printf("Weather HTTP error: %d\n", httpCode);
        http.end();
        return wd;
    }

    String payload = http.getString();
    http.end();

    DynamicJsonDocument doc(2048);
    DeserializationError err = deserializeJson(doc, payload);
    if (err) {
        Serial.print("Weather JSON error: ");
        Serial.println(err.c_str());
        return wd;
    }

    JsonObject daily = doc["daily"];
    wd.tempMax       = daily["temperature_2m_max"][0].as<float>();
    wd.tempMin       = daily["temperature_2m_min"][0].as<float>();
    wd.precipitation = daily["precipitation_sum"][0].as<float>();
    wd.weatherCode   = daily["weathercode"][0].as<int>();
    wd.valid         = true;

    Serial.printf("Weather: code=%d  min=%.1f  max=%.1f  precip=%.1f\n",
                  wd.weatherCode, wd.tempMin, wd.tempMax, wd.precipitation);
    return wd;
}

#define MAX_EVENTS 10

int fetchCalendarEvents(CalEvent events[], int maxEvents) {
    if (WiFi.status() != WL_CONNECTED) return 0;

    struct tm ti;
    if (!getLocalTime(&ti)) return 0;

    char timeMin[32], timeMax[32];
    struct tm startDay = ti;
    startDay.tm_hour = 0; startDay.tm_min = 0; startDay.tm_sec = 0;
    struct tm endDay   = ti;
    endDay.tm_hour   = 23; endDay.tm_min = 59; endDay.tm_sec = 59;

    strftime(timeMin, sizeof(timeMin), "%Y-%m-%dT00:00:00Z", &startDay);
    strftime(timeMax, sizeof(timeMax), "%Y-%m-%dT23:59:59Z", &endDay);

    String calId = String(CALENDAR_ID);
    calId.replace("@", "%40");

    String url = "https://www.googleapis.com/calendar/v3/calendars/";
    url += calId;
    url += "/events?key=";
    url += GOOGLE_API_KEY;
    url += "&timeMin=";
    url += timeMin;
    url += "&timeMax=";
    url += timeMax;
    url += "&singleEvents=true&orderBy=startTime&maxResults=";
    url += maxEvents;

    HTTPClient http;
    http.begin(url);
    int httpCode = http.GET();
    if (httpCode != 200) {
        Serial.printf("Calendar HTTP error: %d\n", httpCode);
        http.end();
        return 0;
    }

    String payload = http.getString();
    http.end();

    DynamicJsonDocument doc(8192);
    DeserializationError err = deserializeJson(doc, payload);
    if (err) {
        Serial.print("Calendar JSON error: ");
        Serial.println(err.c_str());
        return 0;
    }

    JsonArray items = doc["items"].as<JsonArray>();
    int count = 0;
    for (JsonObject item : items) {
        if (count >= maxEvents) break;

        const char* sum = item["summary"] | "(No title)";
        strncpy(events[count].summary, sum, 63);
        events[count].summary[63] = '\0';

        const char* startDt = item["start"]["dateTime"] | "";
        if (strlen(startDt) >= 16) {
            snprintf(events[count].timeStr, sizeof(events[count].timeStr),
                     "%c%c:%c%c", startDt[11], startDt[12], startDt[14], startDt[15]);
        } else {
            strncpy(events[count].timeStr, "All day", sizeof(events[count].timeStr));
        }
        count++;
    }

    Serial.printf("Calendar: %d event(s) fetched.\n", count);
    return count;
}

void printBriefing(WeatherData& wd, CalEvent events[], int eventCount) {
    struct tm ti;
    getLocalTime(&ti);
    char dateStr[32];
    strftime(dateStr, sizeof(dateStr), "%A, %d %B %Y", &ti);

    printer.wake();
    printer.setDefault();

    printer.justify('C');
    printer.boldOn();
    printer.setSize('L');
    printer.println("DAILY BRIEFING");
    printer.setSize('S');
    printer.boldOff();
    printer.println(dateStr);
    printer.feed(1);

    printer.justify('L');
    printer.boldOn();
    printer.println("--- WEATHER (Amsterdam) ---");
    printer.boldOff();

    if (wd.valid) {
        char line[64];
        printer.println(weatherDescription(wd.weatherCode));
        snprintf(line, sizeof(line), "High: %.1f C   Low: %.1f C", wd.tempMax, wd.tempMin);
        printer.println(line);
        snprintf(line, sizeof(line), "Precipitation: %.1f mm", wd.precipitation);
        printer.println(line);
    } else {
        printer.println("(Weather unavailable)");
    }
    printer.feed(1);

    printer.boldOn();
    printer.println("--- TODAY'S APPOINTMENTS ---");
    printer.boldOff();

    if (eventCount == 0) {
        printer.println("No events today.");
    } else {
        for (int i = 0; i < eventCount; i++) {
            char line[80];
            snprintf(line, sizeof(line), "[%s] %s", events[i].timeStr, events[i].summary);
            if (strlen(line) <= 32) {
                printer.println(line);
            } else {
                char l1[48], l2[48];
                snprintf(l1, sizeof(l1), "[%s]", events[i].timeStr);
                snprintf(l2, sizeof(l2), "  %s", events[i].summary);
                printer.println(l1);
                printer.println(l2);
            }
        }
    }
    printer.feed(1);

    printer.boldOn();
    printer.println("--- TO DO TODAY ---");
    printer.boldOff();

    for (int i = 0; i < TODO_LINES; i++) {
        printer.println("[ ] ____________________________");
    }
    printer.feed(3);

    printer.sleep();
    Serial.println("Print complete.");
}

void setup() {
    Serial.begin(115200);
    delay(500);

    Serial.println("=== Daily Briefing Printer ===");

    printerSerial.begin(PRINTER_BAUD, SERIAL_8N1, PRINTER_TX_PIN, PRINTER_RX_PIN);
    printer.begin();

    if (!connectWifi()) {
        printer.wake();
        printer.println("Wi-Fi connection failed!");
        printer.feed(2);
        printer.sleep();
        Serial.println("Halting.");
        while (true) delay(1000);
    }

    syncTime();

    WeatherData wd = fetchWeather();

    CalEvent events[MAX_EVENTS];
    int eventCount = fetchCalendarEvents(events, MAX_EVENTS);

    printBriefing(wd, events, eventCount);

    WiFi.disconnect(true);
    WiFi.mode(WIFI_OFF);
    Serial.println("Done. Deep sleeping...");
    esp_deep_sleep_start();
}

void loop() {
}