maidenhead implemented in screen

src/menu_utils.cpp

@@ -68,8 +68,20 @@ namespace MENU_Utils {
                     }
                 }
                 
-                secondRowMainMenu = utils::createDateString(now()) + "   " + utils::createTimeString(now());
+                const auto time_now = now();
+                secondRowMainMenu = utils::createDateString(time_now) + "   " + utils::createTimeString(time_now);
                 
+                if (time_now % 10 < 5) {
+                    thirdRowMainMenu = String(gps.location.lat(), 4) + " " + String(gps.location.lng(), 4);
+                }
+                else {
+                    thirdRowMainMenu = String(utils::getMaidenheadLocator(gps.location.lat(), gps.location.lng(), 8));
+                }
+
+                for(int i = thirdRowMainMenu.length(); i < 18; i++) {
+                    thirdRowMainMenu += " ";
+                }
+
                 if (gps.hdop.hdop() > 5) {
                     hdopState = "X";
                 } else if (gps.hdop.hdop() > 2 && gps.hdop.hdop() < 5) {
@@ -77,10 +89,7 @@ namespace MENU_Utils {
                 } else if (gps.hdop.hdop() <= 2) {
                     hdopState = "+";
                 }
-                thirdRowMainMenu = String(gps.location.lat(), 4) + " " + String(gps.location.lng(), 4);
-                for(int i = thirdRowMainMenu.length(); i < 18; i++) {
-                    thirdRowMainMenu += " ";
-                }
+        
                 if (gps.satellites.value() > 9) { 
                     thirdRowMainMenu += String(gps.satellites.value()) + hdopState;
                 } else {

src/utils.cpp

@@ -14,6 +14,41 @@ extern String           versionDate;
 
 namespace utils {
 
+  
+  static char locator[11];
+  // The letterize and getMaidenheadLocator functions are
+  // Copyright (c) 2021 Mateusz Salwach
+  // MIT License
+
+  static char letterize(int x) {
+      return (char) x + 65;
+  }
+
+  char *getMaidenheadLocator(double lat, double lon, int size) {
+    double LON_F[]={20,2.0,0.083333,0.008333,0.0003472083333333333};
+    double LAT_F[]={10,1.0,0.0416665,0.004166,0.0001735833333333333};
+    int i;
+    lon += 180;
+    lat += 90;
+
+    if (size <= 0 || size > 10) size = 6;
+    size/=2; size*=2;
+
+    for (i = 0; i < size/2; i++){
+      if (i % 2 == 1) {
+        locator[i*2] = (char) (lon/LON_F[i] + '0');
+        locator[i*2+1] = (char) (lat/LAT_F[i] + '0');
+      } else {
+        locator[i*2] = letterize((int) (lon/LON_F[i]));
+        locator[i*2+1] = letterize((int) (lat/LAT_F[i]));
+      }
+      lon = fmod(lon, LON_F[i]);
+      lat = fmod(lat, LAT_F[i]);
+    }
+    locator[i*2]=0;
+    return locator;
+  }
+
   char *ax25_base91enc(char *s, uint8_t n, uint32_t v) {
     /* Creates a Base-91 representation of the value in v in the string */
     /* pointed to by s, n-characters long. String length should be n+1. */

src/utils.h

@@ -6,6 +6,7 @@
 
 namespace utils {
 
+char *getMaidenheadLocator(double lat, double lon, int size);
 char *ax25_base91enc(char *s, uint8_t n, uint32_t v);
 String createDateString(time_t t);
 String createTimeString(time_t t);