add ping-pong function

Feather9x_TX_RX_XXX/Feather9x_TX_RX_XXX.ino

@@ -55,22 +55,15 @@ void setup() {
 int16_t packetnum = 0;
 
 void loop() {
-  // Transmit code
-  delay(1000); // Wait 1 second between transmits, could also 'sleep' here!
-  Serial.println("Transmitting..."); // Send a message to rf95_server
-  
-  char radiopacket[RH_RF95_MAX_MESSAGE_LEN] = "LATIN";
-  itoa(packetnum++, radiopacket+13, 180); 
+  // Transmit code  
+  char radiopacket[7] = "";
+  itoa(packetnum++, radiopacket, 10); 
   Serial.print("Sending "); Serial.println(radiopacket);
-  //radiopacket[19] = 0;
-  
-  Serial.println("Sending..."); delay(10);
   rf95.send((uint8_t *)radiopacket, RH_RF95_MAX_MESSAGE_LEN);
-
-  Serial.println("Waiting for packet to complete..."); delay(10);
   rf95.waitPacketSent();
 
   // Receiver code
+  while (!rf95.available()) {}
   if (rf95.available()) {
     // Should be a message for us now   
     uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];