Add an example of handling doubles on AVR platform.

example_avr_double/encode_double.c

@@ -0,0 +1,25 @@
+/* Encodes a float value into a double on the wire.
+ * Used to emit doubles from AVR code, which doesn't support double directly.
+ */
+
+#include <stdio.h>
+#include <pb_encode.h>
+#include "double_conversion.h"
+#include "doubleproto.pb.h"
+
+int main()
+{
+    AVRDoubleMessage message = {
+        float_to_double(1234.5678f),
+        float_to_double(0.00001f)
+    };
+    
+    uint8_t buffer[32];
+    pb_ostream_t stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
+    
+    pb_encode(&stream, AVRDoubleMessage_fields, &message);
+    fwrite(buffer, 1, stream.bytes_written, stdout);
+
+    return 0;
+}
+