Feld-Hell sender

#include <WiFi.h>
#include <WebServer.h>
#include <DNSServer.h>

// Define the radio pins
int radioPin = 8;   // GPIO8 for the encoded signal
int audioPin = 10;  // GPIO10 for the 1 kHz tone

// Define the glyph structure and table
typedef struct glyph {
  char ch;
  word col[7];
} Glyph;

const Glyph glyphtab[] PROGMEM = {
  { ' ', { 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000 } },
  { 'A', { 0x07fc, 0x0e60, 0x0c60, 0x0e60, 0x07fc, 0x0000, 0x0000 } },
  { 'B', { 0x0c0c, 0x0ffc, 0x0ccc, 0x0ccc, 0x0738, 0x0000, 0x0000 } },
  { 'C', { 0x0ffc, 0x0c0c, 0x0c0c, 0x0c0c, 0x0c0c, 0x0000, 0x0000 } },
  { 'D', { 0x0c0c, 0x0ffc, 0x0c0c, 0x0c0c, 0x07f8, 0x0000, 0x0000 } },
  { 'E', { 0x0ffc, 0x0ccc, 0x0ccc, 0x0c0c, 0x0c0c, 0x0000, 0x0000 } },
  { 'F', { 0x0ffc, 0x0cc0, 0x0cc0, 0x0c00, 0x0c00, 0x0000, 0x0000 } },
  { 'G', { 0x0ffc, 0x0c0c, 0x0c0c, 0x0ccc, 0x0cfc, 0x0000, 0x0000 } },
  { 'H', { 0x0ffc, 0x00c0, 0x00c0, 0x00c0, 0x0ffc, 0x0000, 0x0000 } },
  { 'I', { 0x0ffc, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000 } },
  { 'J', { 0x003c, 0x000c, 0x000c, 0x000c, 0x0ffc, 0x0000, 0x0000 } },
  { 'K', { 0x0ffc, 0x00c0, 0x00e0, 0x0330, 0x0e1c, 0x0000, 0x0000 } },
  { 'L', { 0x0ffc, 0x000c, 0x000c, 0x000c, 0x000c, 0x0000, 0x0000 } },
  { 'M', { 0x0ffc, 0x0600, 0x0300, 0x0600, 0x0ffc, 0x0000, 0x0000 } },
  { 'N', { 0x0ffc, 0x0700, 0x01c0, 0x0070, 0x0ffc, 0x0000, 0x0000 } },
  { 'O', { 0x0ffc, 0x0c0c, 0x0c0c, 0x0c0c, 0x0ffc, 0x0000, 0x0000 } },
  { 'P', { 0x0c0c, 0x0ffc, 0x0ccc, 0x0cc0, 0x0780, 0x0000, 0x0000 } },
  { 'Q', { 0x0ffc, 0x0c0c, 0x0c3c, 0x0ffc, 0x000f, 0x0000, 0x0000 } },
  { 'R', { 0x0ffc, 0x0cc0, 0x0cc0, 0x0cf0, 0x079c, 0x0000, 0x0000 } },
  { 'S', { 0x078c, 0x0ccc, 0x0ccc, 0x0ccc, 0x0c78, 0x0000, 0x0000 } },
  { 'T', { 0x0c00, 0x0c00, 0x0ffc, 0x0c00, 0x0c00, 0x0000, 0x0000 } },
  { 'U', { 0x0ff8, 0x000c, 0x000c, 0x000c, 0x0ff8, 0x0000, 0x0000 } },
  { 'V', { 0x0ffc, 0x0038, 0x00e0, 0x0380, 0x0e00, 0x0000, 0x0000 } },
  { 'W', { 0x0ff8, 0x000c, 0x00f8, 0x000c, 0x0ff8, 0x0000, 0x0000 } },
  { 'X', { 0x0e1c, 0x0330, 0x01e0, 0x0330, 0x0e1c, 0x0000, 0x0000 } },
  { 'Y', { 0x0e00, 0x0380, 0x00fc, 0x0380, 0x0e00, 0x0000, 0x0000 } },
  { 'Z', { 0x0c1c, 0x0c7c, 0x0ccc, 0x0f8c, 0x0e0c, 0x0000, 0x0000 } },
  { '0', { 0x07f8, 0x0c0c, 0x0c0c, 0x0c0c, 0x07f8, 0x0000, 0x0000 } },
  { '1', { 0x0300, 0x0600, 0x0ffc, 0x0000, 0x0000, 0x0000, 0x0000 } },
  { '2', { 0x061c, 0x0c3c, 0x0ccc, 0x078c, 0x000c, 0x0000, 0x0000 } },
  { '3', { 0x0006, 0x1806, 0x198c, 0x1f98, 0x00f0, 0x0000, 0x0000 } },
  { '4', { 0x1fe0, 0x0060, 0x0060, 0x0ffc, 0x0060, 0x0000, 0x0000 } },
  { '5', { 0x000c, 0x000c, 0x1f8c, 0x1998, 0x18f0, 0x0000, 0x0000 } },
  { '6', { 0x07fc, 0x0c66, 0x18c6, 0x00c6, 0x007c, 0x0000, 0x0000 } },
  { '7', { 0x181c, 0x1870, 0x19c0, 0x1f00, 0x1c00, 0x0000, 0x0000 } },
  { '8', { 0x0f3c, 0x19e6, 0x18c6, 0x19e6, 0x0f3c, 0x0000, 0x0000 } },
  { '9', { 0x0f80, 0x18c6, 0x18cc, 0x1818, 0x0ff0, 0x0000, 0x0000 } },
  { '*', { 0x018c, 0x0198, 0x0ff0, 0x0198, 0x018c, 0x0000, 0x0000 } },
  { '.', { 0x001c, 0x001c, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000 } },
  { '?', { 0x1800, 0x1800, 0x19ce, 0x1f00, 0x0000, 0x0000, 0x0000 } },
  { '!', { 0x1f9c, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000 } },
  { '(', { 0x01e0, 0x0738, 0x1c0e, 0x0000, 0x0000, 0x0000, 0x0000 } },
  { ')', { 0x1c0e, 0x0738, 0x01e0, 0x0000, 0x0000, 0x0000, 0x0000 } },
  { '#', { 0x0330, 0x0ffc, 0x0330, 0x0ffc, 0x0330, 0x0000, 0x0000 } },
  { '$', { 0x078c, 0x0ccc, 0x1ffe, 0x0ccc, 0x0c78, 0x0000, 0x0000 } },
  { '/', { 0x001c, 0x0070, 0x01c0, 0x0700, 0x1c00, 0x0000, 0x0000 } }
};

#define NGLYPHS (sizeof(glyphtab) / sizeof(glyphtab[0]))

// Web server and DNS server
WebServer server(80);
DNSServer dnsServer;

// Variables
String text = "";
String binaryString = "";
bool isSending = false;
unsigned long lastTransmitTime = 0;
int currentBitIndex = 0;

// Function to compile text into a binary string
String compileTextToBinary(const char *text) {
  String binaryString = "";
  for (int i = 0; text[i] != '\0'; i++) {
    char ch = text[i];
    Serial.print(ch);
    Serial.print(" -> ");
    for (int j = 0; j < NGLYPHS; j++) {
      if (pgm_read_byte(&glyphtab[j].ch) == ch) {
        for (int x = 0; x < 7; x++) {
          word col = pgm_read_word(&glyphtab[j].col[x]);
          for (int y = 0; y < 14; y++) {
            binaryString += (col & (1 << y)) ? '1' : '0';
            Serial.print((col & (1 << y)) ? '1' : '0');
          }
        }
        break;
      }
    }
    Serial.println();
  }
  Serial.println("Total:" + binaryString);
  return binaryString;
}

// Function to transmit one bit
void transmitBit(char bit) {
  digitalWrite(radioPin, bit == '1' ? HIGH : LOW);

  // Modulate GPIO10 with 1 kHz tone when GPIO8 is HIGH
  if (bit == '1') {
    tone(audioPin, 1000);  // Generate 1 kHz tone
  } else {
    noTone(audioPin);  // Turn off the tone
  }
}

// Web interface handlers
void handleRoot() {
  String html = "<!DOCTYPE html>"
                "<html>"
                "<head>"
                "<title>Feld-Hell Transmitter</title>"
                "<style>"
                "body { font-family: Arial, sans-serif; text-align: center; margin-top: 50px; }"
                "textarea { width: 300px; height: 100px; margin-bottom: 20px; }"
                "#sendButton { padding: 10px 20px; font-size: 16px; cursor: pointer; border: none; border-radius: 5px; color: white; }"
                ".green { background-color: green; }"
                ".red { background-color: red; }"
                ".disabled { background-color: #ccc; cursor: not-allowed; }"
                "</style>"
                "<script>"
                "function toggleSend() {"
                "const text = document.getElementById('text').value.toUpperCase();"
                "const sendButton = document.getElementById('sendButton');"
                "const textArea = document.getElementById('text');"
                "if (sendButton.classList.contains('green')) {"
                "fetch('/send', {"
                "method: 'POST',"
                "headers: { 'Content-Type': 'application/x-www-form-urlencoded' },"
                "body: 'text=' + encodeURIComponent(text)"
                "}).then(response => {"
                "if (response.ok) {"
                "sendButton.classList.remove('green');"
                "sendButton.classList.add('red');"
                "sendButton.textContent = 'Stop Sending';"
                "textArea.disabled = true;"
                "textArea.classList.add('disabled');"
                "}"
                "});"
                "} else {"
                "fetch('/stop').then(response => {"
                "if (response.ok) {"
                "sendButton.classList.remove('red');"
                "sendButton.classList.add('green');"
                "sendButton.textContent = 'Send';"
                "textArea.disabled = false;"
                "textArea.classList.remove('disabled');"
                "}"
                "});"
                "}"
                "}"
                "</script>"
                "</head>"
                "<body>"
                "<h1>Feld-Hell Transmitter</h1>"
                "<textarea id=\"text\" placeholder=\"Enter text here\"></textarea><br>"
                "<button id=\"sendButton\" class=\"green\" onclick=\"toggleSend()\">Send</button>"
                "</body>"
                "</html>";
  server.send(200, "text/html", html);
}

void handleSend() {
  if (server.hasArg("text")) {
    text = server.arg("text");
    binaryString = compileTextToBinary(text.c_str());
    isSending = true;
    currentBitIndex = 0;
    lastTransmitTime = micros();  // Use micros() for precise timing
    server.send(200, "text/plain", "Sending started");
  } else {
    server.send(400, "text/plain", "Error: No text provided");
  }
}

void handleStop() {
  isSending = false;
  digitalWrite(radioPin, LOW);  // Ensure the signal ends low
  noTone(audioPin);             // Ensure the tone is turned off
  server.send(200, "text/plain", "Sending stopped");
}

void setup() {
  digitalWrite(LED_BUILTIN, LOW);

  // Start Serial communication
  Serial.begin(115200);
  while (!Serial) delay(100);  // wait until serial is up

  // Set the radio and audio pins as output
  pinMode(radioPin, OUTPUT);
  pinMode(audioPin, OUTPUT);

  // Start Wi-Fi access point
  WiFi.softAP("Feld-Hell Transmitter");
  IPAddress IP = WiFi.softAPIP();
  Serial.println("Access Point IP: " + IP.toString());

  // Start DNS server for captive portal
  dnsServer.start(53, "*", IP);

  // Set up web server routes
  server.on("/", handleRoot);
  server.on("/send", HTTP_POST, handleSend);
  server.on("/stop", handleStop);

  // Start the web server
  server.begin();
  digitalWrite(LED_BUILTIN, HIGH);
}

void loop() {
  // Handle DNS and web server requests
  dnsServer.processNextRequest();
  server.handleClient();

  // Non-blocking transmission with precise timing
  if (isSending && (micros() - lastTransmitTime >= 4080)) {
    if (currentBitIndex < binaryString.length()) {
      transmitBit(binaryString[currentBitIndex]);
      currentBitIndex++;
    } else {
      // Restart transmission from the beginning
      currentBitIndex = 0;
    }
    lastTransmitTime = micros();  // Reset the timer
  }
}