 void loop()
 {
   if (Serial.available()){
-    result_format = Serial.read();
+    command = Serial.read();
+    if ('I' == command){
+      Serial.println(ID);
+      return;
+    }
+    if ('W' == command){
+      ID = Serial.parseInt();
+      EEPROM.put(ID_location, ID);
+      return;
+    }
     sample_pending = true;
     dmm.sync();
   }
 
   if (dmm.poll() && sample_pending){
     sample_pending = false;
-    switch(result_format){
+    switch(command){
     case 'n': // number only
     default:
       Serial.println(dmm.asciiValue());

  while(!Serial){
    // busy wait
  }

  dmm.setPort(dmm_port, rx_pin);
  sample_pending = false;

// Copyright (C) 2016 Theodore C. Yapo

#include <SoftwareSerial.h>
#include <EEPROM.h>

class DMM
{
