add routine to output waypoint data

src/gps/NMEAWPL.cpp

@@ -0,0 +1,26 @@
+#include "NMEAWPL.h"
+
+/* -------------------------------------------
+ *        1       2 3        4 5    6
+ *        |       | |        | |    |
+ * $--WPL,llll.ll,a,yyyyy.yy,a,c--c*hh<CR><LF>
+ *
+ * Field Number:
+ * 1 Latitude
+ * 2 N or S (North or South)
+ * 3 Longitude
+ * 4 E or W (East or West)
+ * 5 Waypoint name
+ * 6 Checksum
+ */
+
+uint printWPL(char *buf, Position &pos, const char *name)
+{
+    uint len = sprintf(buf, "$GNWPL,%07.2f,%c,%08.2f,%c,%s", pos.latitude_i * 1e-5, pos.latitude_i < 0 ? 'S' : 'N', pos.longitude_i * 1e-5, pos.longitude_i < 0 ? 'W' : 'E', name);
+    uint chk = 0;
+    for (uint i = 1; i < len; i++) {
+        chk ^= buf[i];
+    }
+    len += sprintf(buf + len, "*%02X\r\n", chk);
+    return len;
+}

src/gps/NMEAWPL.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <Arduino.h>
+#include "main.h"
+
+uint printWPL(char *buf, Position &pos, const char *name);