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diff --git a/sketch/sketch.ino b/sketch/sketch.ino
index 177849c..f8f4892 100644
--- a/sketch/sketch.ino
+++ b/sketch/sketch.ino
@@ -4,6 +4,15 @@
 #include <ArduinoModbus.h>
 
 
+#define RX_PIN 7
+#define TX_PIN 6
+#define RE_PIN 5
+#define DE_PIN 4
+#define LED_RED 3
+#define LED_GREEN 2
+#define LED_BLUE 45
+
+
 
 /* OTAA para*/
 uint8_t devEui[] = { 0x22, 0x32, 0x33, 0x00, 0x00, 0x88, 0x88, 0x02 };
@@ -62,6 +71,7 @@ uint8_t appPort = 2;
 uint8_t confirmedNbTrials = 4;
 
 RS485Class* pRS485_1; 
+ModbusRTUClientClass* pModbusClient;
 
 /* Prepares the payload of the frame */
 static void prepareTxFrame( uint8_t port )
@@ -73,11 +83,24 @@ static void prepareTxFrame( uint8_t port )
   *for example, if use REGION_CN470, 
   *the max value for different DR can be found in MaxPayloadOfDatarateCN470 refer to DataratesCN470 and BandwidthsCN470 in "RegionCN470.h".
   */
-    appDataSize = 4;
-    appData[0] = 0x10;
-    appData[1] = 0x21;
-    appData[2] = 0x32;
-    appData[3] = 0x43;
+    appDataSize = 8;
+
+    Serial.println("modbus operation");
+
+    long v1 = pModbusClient->inputRegisterRead(7, 0x01);
+    Serial.print("v1: ");
+    Serial.println(v1);
+    memcpy(appData, &v1, 4);
+
+    long v2 = pModbusClient->inputRegisterRead(7, 0x02);
+    Serial.print("v2: ");
+    Serial.println(v2);
+    memcpy(appData+4, &v2, 4);
+    
+    //appData[0] = 0x10;
+    //appData[1] = 0x21;
+    //appData[2] = 0x32;
+    //appData[3] = 0x43;
 }
 
 //if true, next uplink will add MOTE_MAC_DEVICE_TIME_REQ 
@@ -85,10 +108,18 @@ static void prepareTxFrame( uint8_t port )
 
 void setup() {
   Serial.begin(115200);
-  Serial1.begin(9600, SERIAL_8N1, 7, 6);
-  pRS485_1 = new RS485Class(Serial1, 6, 5, 4);
-  ModbusRTUClient.begin(*pRS485_1, 9600, SERIAL_8N1);
+  Serial1.begin(9600, SERIAL_8N1, RX_PIN, TX_PIN);
+  pRS485_1 = new RS485Class(Serial1, TX_PIN, RE_PIN, DE_PIN);
+  pModbusClient = new ModbusRTUClientClass(*pRS485_1);
+  pModbusClient->begin(9600, SERIAL_8N1);
   
+  pinMode(LED_BLUE, OUTPUT);
+  digitalWrite(LED_BLUE, LOW);
+  pinMode(LED_RED, OUTPUT);
+  digitalWrite(LED_RED, LOW);
+  pinMode(LED_GREEN, OUTPUT);
+  digitalWrite(LED_GREEN, LOW);
+
   Mcu.begin();
   deviceState = DEVICE_STATE_INIT;
 }
@@ -97,9 +128,12 @@ void loop()
 {
 #if 1
   
+  digitalWrite(LED_GREEN, HIGH);
+
   switch( deviceState )
   {
     case DEVICE_STATE_INIT:
+    digitalWrite(LED_GREEN, LOW);
     {
 #if(LORAWAN_DEVEUI_AUTO)
       LoRaWAN.generateDeveuiByChipID();
@@ -113,12 +147,8 @@ void loop()
       break;
     }
     case DEVICE_STATE_SEND:
+    digitalWrite(LED_BLUE, HIGH);
     {
-      Serial.println("rs485 writing");
-      pRS485_1->beginTransmission();
-      pRS485_1->write(0xaa);
-      pRS485_1->endTransmission();
-      
       Serial.println("sending");
       prepareTxFrame( appPort );
       LoRaWAN.send();
@@ -126,6 +156,7 @@ void loop()
       break;
     }
     case DEVICE_STATE_CYCLE:
+    digitalWrite(LED_BLUE, LOW);
     {
       // Schedule next packet transmission
       txDutyCycleTime = appTxDutyCycle + randr( -APP_TX_DUTYCYCLE_RND, APP_TX_DUTYCYCLE_RND );