         df_append((const char*) rf12_data - 2, rf12_len + 2);
 #endif
       if (RF12_WANTS_ACK && (config.nodeId & COLLECT) == 0) {
-        Serial.println(" -> ack");
+        Serial.print(" -> ack ");
 /// Debug code
         testCounter = 0;
         if ((rf12_hdr & RF12_HDR_MASK) == 31) {          // Special Node 31?
-          testbuf[0] = 67; // "C"
+          for (byte i = 0; i < 31; i++) {
+            if (nodes[i] == 0xFF) {            
+              testbuf[0] = i;
+              break;
+            }
+          }
           testCounter = 1;
+          Serial.print(testbuf[0]);
         }
         rf12_sendStart(RF12_ACK_REPLY, testbuf, testCounter);
+        Serial.println();
 /// Debug code
       }
       

    frequency = 1600; 
  else // Lose flag nibble to get frequency high order
    frequency = ((frequency & 0x0F)  << 8) + (eeprom_read_byte(RF12_EEPROM_ADDR + 3));
}
void loop() {
  if (Serial.available())

static int value;
static byte stack[RF12_MAXDATA+4], top, sendLen, dest;
static byte testbuf[RF12_MAXDATA], testCounter, useHex;
static byte nodes[31];
static byte band;

void displayVersion(uint8_t newline );
