Repo on the way

Author: embedded4ever

.gitignore

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+.pio
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch
+.pioenvs
+.piolibdeps
+*.out

.vscode/extensions.json

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+{
+    // See http://go.microsoft.com/fwlink/?LinkId=827846
+    // for the documentation about the extensions.json format
+    "recommendations": [
+        "platformio.platformio-ide"
+    ],
+    "unwantedRecommendations": [
+        "ms-vscode.cpptools-extension-pack"
+    ]
+}

README.md

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+### This project displays a daily C++ quiz question from cppquiz.org on an e-paper display powered by an ESP32 microcontroller. Questions are fetched via Google Apps Script connected to a Google Sheets backend, then rendered with clean formatting on a 7.5" E-Ink screen.
+
+<p align="center">
+  <img src="photos/onwifi.png" alt="E-paper device showing C++ quiz" width="400"/>
+</p>
+
+## 🚀 Features
+
+- Displays C++ quiz question from a Google Sheet
+- Works offline by caching the last successful question
+- Uses deep sleep to save power (wakes up every hour)
+- Shows Wi-Fi status for shown question (connected/disconnected) with an icon
+- Fully customizable via Google Sheets + Apps Script backend
+
+
+## 📦 Hardware
+
+- ESP32 
+- Waveshare ESP32 Epaper Driver Board 
+- Waveshare 7.5" E-Paper Display
+
+
+## 🧠 How It Works
+
+- ESP32 boots and connects to Wi-Fi.
+- It sends an HTTP request to a Google Apps Script endpoint.
+- The Apps Script reads a  unshown question from Google Sheets and returns it as plain text.
+- ESP32 displays the question on the e-paper screen.
+- If Wi-Fi fails, it loads the last cached question.
+- Device goes into deep sleep and repeats after one hour.
+
+
+## 🎉 To Build Yourself
+
+- ### Software
+
+  - Upload an Excel file ([questions.xlsx](cppquiz_questions.xlsx)) to Google Drive
+  - Open it with Google Sheets
+  - In your Google Sheet: 
+      - Click Extensions > Apps Script
+      - Paste the code.gs ([code.gs](code.gs))
+  - Deploy the script as a Web App
+  - Set access to "Anyone with the link"
+  - 
+    Update `code.gs`  ([code.gs](code.gs)):
+    ```js
+    var sheet_id = "YOUR_GOOGLE_SHEET_ID"; //Excel
+    ```
+
+
+- ### Hardware 
+
+  Update `config.h`  ([config.h](include/config.h))on ESP32 firmware:
+
+  ```cpp
+  const std::string WIFI_SSID         = "YOUR_WIFI_SSID";
+  const std::string WIFI_PWD          = "YOUR_WIFI_PWD"
+  const std::string GS_DEPLOYMENT_ID  = "YOUR_GS_DEPLOYMENT_ID"
+  ```
+
+## 📄 Why Use an Excel File?
+
+The questions displayed on this device are sourced from [cppquiz.org](https://cppquiz.org/), which provides a comprehensive collection of C++ questions. However, the site does not offer an API to fetch individual questions by ID.
+
+Instead, all questions are made available as a bulk JSON file at:
+
+https://static.cppquiz.org/published.json
+
+Due to the size of this dataset and the need for easier navigation, filtering, and tracking of displayed questions, I chose to manage the content through a Google Sheets with Google App Script.
+
+
+
+<a href="https://buymeacoffee.com/vvolkanunas" target="_blank"><img src="https://www.buymeacoffee.com/assets/img/custom_images/orange_img.png" alt="Buy Me A Coffee" style="height: 41px !important;width: 174px !important;box-shadow: 0px 3px 2px 0px rgba(190, 190, 190, 0.5) !important;-webkit-box-shadow: 0px 3px 2px 0px rgba(190, 190, 190, 0.5) !important;" ></a>

code.gs

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+var sheet_id = "YOUR_GOOGLE_SHEET_ID";  // Google Sheet ID
+var ss = SpreadsheetApp.openById(sheet_id);
+var sheet = ss.getSheets()[0];  // Get the first sheet in the spreadsheet
+
+/** 
+ * Handles HTTP GET requests.
+ * Expected parameter: ?read=question
+ */
+function doGet(e) {
+  var arg = e.parameter.read;
+  
+  // If no valid parameter is provided
+  if (arg == undefined){
+    return ContentService.createTextOutput("error: invalid request");
+  }
+
+  // If the request is for a question, return a new question
+  if (arg == "question"){
+    return getIter();
+  }
+
+  // For any other unexpected request
+  return ContentService.createTextOutput("error: unexpected request"); 
+}
+
+/**
+ * Finds the next question, marks it as shown, and returns its data.
+ */
+function getIter() {
+  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
+  
+  var row = 2;  // Start checking from row 2 (assuming row 1 is header)
+
+  // Find the first row in column H without a checkmark
+  while (sheet.getRange("H" + row).getValue() !== "") {
+    row++; 
+  }
+
+  // Get question data from columns A, B, and G for the current row
+  var question = sheet.getRange("B" + row).getDisplayValue(); 
+  var difficulty = sheet.getRange("G" + row).getDisplayValue(); 
+  var question_id = sheet.getRange("A" + row).getDisplayValue(); 
+
+  // Mark this question as used by putting a checkmark in column H
+  sheet.getRange("H" + row).setValue("✓"); 
+
+  // Prepare the response string
+  var res = "Question #" + question_id + " Difficulty : " + difficulty + "\n\n" + question;
+  
+  Logger.log(res);
+
+  // Return the result as a plain text HTTP response
+  return ContentService.createTextOutput(res);
+}

cppquiz_questions.xlsx

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+#ifndef NO_WIFI_H
+#define NO_WIFI_H
+
+#include <Arduino.h>
+
+// 48 x 48
+const unsigned char wifi_on_48x48[] PROGMEM = {
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x03, 0xff, 0xff,
+	0xff, 0xfc, 0x00, 0x00, 0x3f, 0xff, 0xff, 0xf0, 0x00, 0x00, 0x0f, 0xff,
+	0xff, 0x80, 0x1f, 0xf8, 0x01, 0xff, 0xff, 0x01, 0xff, 0xff, 0x80, 0xff,
+	0xfc, 0x0f, 0xff, 0xff, 0xf0, 0x3f, 0xf8, 0x3f, 0xff, 0xff, 0xfc, 0x1f,
+	0xe0, 0xff, 0xff, 0xff, 0xff, 0x07, 0xe1, 0xff, 0xff, 0xff, 0xff, 0x87,
+	0xe3, 0xff, 0xe0, 0x07, 0xff, 0xcf, 0xff, 0xff, 0x00, 0x00, 0xff, 0xff,
+	0xff, 0xfc, 0x00, 0x00, 0x3f, 0xff, 0xff, 0xf0, 0x0f, 0xf0, 0x0f, 0xff,
+	0xff, 0xc0, 0xff, 0xff, 0x03, 0xff, 0xff, 0x83, 0xff, 0xff, 0xc1, 0xff,
+	0xff, 0x87, 0xff, 0xff, 0xe1, 0xff, 0xff, 0xdf, 0xff, 0xff, 0xfb, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xf0, 0x0f, 0xff, 0xff,
+	0xff, 0xff, 0xc0, 0x03, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0xff, 0xff,
+	0xff, 0xfe, 0x07, 0xe0, 0x7f, 0xff, 0xff, 0xfe, 0x3f, 0xfc, 0x7f, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xfe, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xfc, 0x3f, 0xff, 0xff,
+	0xff, 0xff, 0xfc, 0x3f, 0xff, 0xff, 0xff, 0xff, 0xfc, 0x3f, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
+  };
+
+// 48 x 48
+const unsigned char wifi_off_48x48[] PROGMEM = {
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0x3f, 0xff, 0xff, 0xff, 0xff, 0xff, 0x1f, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0x0f, 0xff, 0xff, 0xff, 0xff, 0xff, 0x87, 0xe0, 0x03, 0xff, 0xff,
+	0xff, 0xc3, 0xe0, 0x00, 0x3f, 0xff, 0xff, 0xe1, 0xe0, 0x00, 0x0f, 0xff,
+	0xff, 0xc0, 0xff, 0xf8, 0x01, 0xff, 0xff, 0x00, 0xff, 0xff, 0x80, 0xff,
+	0xfc, 0x08, 0x7f, 0xff, 0xf0, 0x3f, 0xf8, 0x3c, 0x3f, 0xff, 0xfc, 0x1f,
+	0xe0, 0xfe, 0x1f, 0xff, 0xff, 0x07, 0xe1, 0xff, 0x0f, 0xff, 0xff, 0x87,
+	0xe3, 0xff, 0x87, 0xf7, 0xff, 0xcf, 0xff, 0xff, 0x03, 0xe0, 0xff, 0xff,
+	0xff, 0xfc, 0x01, 0xe0, 0x3f, 0xff, 0xff, 0xf0, 0x00, 0xf0, 0x0f, 0xff,
+	0xff, 0xc0, 0xf8, 0x7f, 0x03, 0xff, 0xff, 0x83, 0xfc, 0x3f, 0xc1, 0xff,
+	0xff, 0x87, 0xfc, 0x3f, 0xe1, 0xff, 0xff, 0xdf, 0xfe, 0x1f, 0xfb, 0xff,
+	0xff, 0xff, 0xff, 0x0f, 0xff, 0xff, 0xff, 0xff, 0xf0, 0x07, 0xff, 0xff,
+	0xff, 0xff, 0xc0, 0x03, 0xff, 0xff, 0xff, 0xff, 0x00, 0x01, 0xff, 0xff,
+	0xff, 0xfe, 0x07, 0xe0, 0xff, 0xff, 0xff, 0xfe, 0x3f, 0xf8, 0x7f, 0xff,
+	0xff, 0xff, 0xff, 0xfc, 0x3f, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x1f, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0x0f, 0xff, 0xff, 0xff, 0xff, 0xff, 0x0f, 0xff,
+	0xff, 0xff, 0xfe, 0x7f, 0x87, 0xff, 0xff, 0xff, 0xfc, 0x3f, 0xc3, 0xff,
+	0xff, 0xff, 0xfc, 0x3f, 0xe1, 0xff, 0xff, 0xff, 0xfc, 0x3f, 0xf0, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xf8, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfc, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
+  };
+
+#endif

include/assets/wifi.h

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+#ifndef CONFIG_H
+#define CONFIG_H
+
+#include <string>
+
+#define WS_BOARD
+
+const uint8_t PIN_EPD_BUSY  = 25;
+const uint8_t PIN_EPD_CS    = 15;
+const uint8_t PIN_EPD_RST   = 26;
+const uint8_t PIN_EPD_DC    = 27;
+
+// WiFi credentials
+const std::string WIFI_SSID = "YOUR_WIFI_SSID";
+const std::string WIFI_PWD  = "YOUR_WIFI_PWD";
+
+// Google Apps Script Deployment ID
+const std::string GS_DEPLOYMENT_ID  = "YOUR_GS_DEPLOYMENT_ID";
+// Base URL for accessing the Google Apps Script
+const std::string BASE_URL          = "https://script.google.com/macros/s/" + GS_DEPLOYMENT_ID + "/exec?read=";
+
+// Query parameter for requesting a question
+const std::string QUESTION_TAG = "question";
+// Final URL used to fetch a question
+const std::string QUESTION_URL = BASE_URL + QUESTION_TAG;
+
+// Sleep duration in us
+constexpr uint64_t SLEEP_DURATION_US = 60ULL * 1000'000 * 60;
+
+
+#endif  

include/config.h

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+#ifndef DISPLAY_UTILS_H
+#define DISPLAY_UTILS_H
+
+#include <GxEPD2_BW.h>
+#include <SPI.h>
+
+#include "assets/wifi.h"
+#include "fonts/FreeSans.h"
+#include "fonts/UbuntuMono_R.h"
+#include "config.h"
+
+// Macro to disallow copying and assignment for the Display class
+#define DISALLOW_COPY_AND_ASSIGN(TypeName) \
+  TypeName(const TypeName&) = delete;      \
+  void operator=(const TypeName&) = delete;
+
+// Generic Display class template for rendering content to an e-ink display
+template <typename DisplayType>
+class Display 
+{
+  public:
+
+    // Constructor initializes display and SPI if on WS_BOARD
+    Display()
+      : m_display(DisplayType(PIN_EPD_CS, PIN_EPD_DC, PIN_EPD_RST, PIN_EPD_BUSY))
+        #ifdef WS_BOARD
+          , m_hspi(HSPI)
+        #endif
+    {}
+
+    // Initializes display and sets rotation
+    void begin() 
+    {
+      #ifdef WS_BOARD
+        // Initialize SPI with custom pins (specific to WS_BOARD)
+        m_hspi.begin(13, 12, 14, 15); 
+        m_display.epd2.selectSPI(m_hspi, SPISettings(4000000, MSBFIRST, SPI_MODE0));
+      #endif
+      m_display.init(115200);
+      m_display.setRotation(1);
+      m_display.setTextSize(1);
+      m_display.setTextColor(GxEPD_BLACK);
+      m_display.fillScreen(GxEPD_WHITE); 
+    }
+
+    // Renders the full display including header, question, WiFi icon, and content
+    void render(const String& ret, const bool connection_status)
+    {
+      printHeader();      // Display the title
+      printQuestion();    // Display the prompt question
+
+      // Display WiFi icon depending on connection status
+      displayBitmap(connection_status ? wifi_on_48x48 : wifi_off_48x48);  
+
+      // Display the question content
+      m_display.setFont(&UbuntuMono_R_12pt7b);
+      m_display.setCursor(0, 150);
+      m_display.print(ret);    
+
+      m_display.display();        
+      m_display.powerOff();      
+    }   
+
+  private:
+
+    // Draws the WiFi icon bitmap (connected or disconnected)
+    void displayBitmap(const uint8_t* bitmap)
+    {
+      m_display.drawInvertedBitmap(DisplayType::HEIGHT - 48, 0, bitmap, 48, 48, GxEPD_BLACK);
+    }
+
+    // Displays the header text centered at the top of the screen
+    void printHeader() 
+    {
+      m_display.setFont(&FreeSans_16pt7b);
+      const char Header[] = "C++ Quiz - cppquiz.org!";
+      int16_t tbx, tby; 
+      uint16_t tbw, tbh;
+      m_display.getTextBounds(Header, 0, 0, &tbx, &tby, &tbw, &tbh);
+      uint16_t x = ((m_display.width() - tbw) / 2) - tbx;
+      m_display.setCursor(x, tbh);  
+      m_display.print(Header);
+    }
+
+    // Displays the static question prompt
+    void printQuestion() 
+    {
+      m_display.setFont(&FreeSans_12pt7b);
+      const char Question[] = "According to the C++23 standard, what is the output of this program?";      
+      m_display.setCursor(0, 75);
+      m_display.print(Question);
+    }
+
+    using EinkDisplay = GxEPD2_BW<DisplayType, DisplayType::HEIGHT>;
+
+    #ifdef WS_BOARD
+      SPIClass m_hspi; // SPI instance for WS_BOARD
+    #endif
+    EinkDisplay m_display; // E-ink display driver
+
+    DISALLOW_COPY_AND_ASSIGN(Display)
+};
+
+#endif

include/display_utils.h

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+#ifndef __FONTS_ALLERTASTENCIL_REGULAR_H__
+#define __FONTS_ALLERTASTENCIL_REGULAR_H__
+#include "AllertaStencil_Regular/AllertaStencil_Regular_12pt7b.h"
+#include "AllertaStencil_Regular/AllertaStencil_Regular_16pt7b.h"
+#include "AllertaStencil_Regular/AllertaStencil_Regular_20pt7b.h"
+#include "AllertaStencil_Regular/AllertaStencil_Regular_26pt7b.h"
+#include "AllertaStencil_Regular/AllertaStencil_Regular_32pt7b.h"
+#include "AllertaStencil_Regular/AllertaStencil_Regular_40pt7b.h"
+#include "AllertaStencil_Regular/AllertaStencil_Regular_48pt7b.h"
+#include "AllertaStencil_Regular/AllertaStencil_Regular_6pt7b.h"
+#endif