Added uptime of the device.

OpenFlightTX.ino

@@ -3,11 +3,6 @@
  * Manual - https://www.seeedstudio.com/blog/2019/07/05/u8g2-for-seeeduino-boards/
  * Dual OLED - https://github.com/olikraus/u8g2/issues/77
  *
- * TODO:
- * [   ] - Binding with receiver
- * [   ] - HostAP for the receiver to bind
- * [   ] - Changing transmission code
- * 
  * Every power cycle:
  * 1. Read configuration from EEPROM
  *  
@@ -412,7 +407,7 @@ void setup_webserver(void) {
     /*** Index Page ***/
     server.on("/", HTTP_GET, []() {
         server.sendHeader("Connection", "close");
-        server.send(200, "text/html", index_html);
+        server.send(200, "text/html", firmware_upgrade_html);
     });
 
     /*** Firmware Upgrade Page ***/
@@ -1531,6 +1526,10 @@ void rc_controller(void) {
     // u8g2_right.drawFilledEllipse(gimbal_x, gimbal_y, 3, 3, U8G2_DRAW_ALL);
     u8g2_left.drawFilledEllipse(90 + gimbal_x, 31 + gimbal_y, 2, 2, U8G2_DRAW_ALL);
 
+    // Calculate uptime
+    int hours = uptime / 3600;
+    int minutes = uptime / 60;
+    int seconds = uptime % 60;
    
     u8g2_left.setFont(u8g2_font_5x7_tf);
     sprintf(buf, "%d packets/s", nrf_profiling);
@@ -1538,6 +1537,9 @@ void rc_controller(void) {
     sprintf(buf, "%d MHz", freq_channel + 2400);
     u8g2_left.drawStr(0, 32, buf);
 
+    sprintf(buf, "%02d:%02d:%02d", hours, minutes, seconds);
+    u8g2_left.drawStr(84, 24, buf);
+
     switch(freq_txpower) {
         case 0:
             sprintf(buf, "TX MIN");