diff --git a/src/Sim800.cpp b/src/Sim800.cpp
index ab2ac14..efdd12c 100644
--- a/src/Sim800.cpp
+++ b/src/Sim800.cpp
@@ -32,6 +32,7 @@ const char SLEEP_MODE_2[] PROGMEM = "AT+CSCLK=2\r\n";
 const char SLEEP_MODE_1[] PROGMEM = "AT+CSCLK=1\r\n";
 const char SLEEP_MODE_0[] PROGMEM = "AT+CSCLK=0\r\n";
 const char AT_OK[] PROGMEM = "OK";
+const char AT[] PROGMEM = "AT\r\n";
 
 int SIM800::preInit(void)
 {
@@ -97,7 +98,7 @@ void SIM800::cleanBuffer(char *buffer, int count)
 
 void SIM800::sendCmd(const char *cmd, unsigned int delayBeforeSend)
 {
-    serialSIM800.listen();
+    //serialSIM800.listen();
     serialSIM800.flush();
     delay(delayBeforeSend);
     write(cmd);
@@ -106,7 +107,7 @@ void SIM800::sendCmd(const char *cmd, unsigned int delayBeforeSend)
 
 int SIM800::sendATTest(void)
 {
-    int ret = sendCmdAndWaitForResp("AT\r\n", "OK", DEFAULT_TIMEOUT);
+    int ret = sendCmdAndWaitForResp_P(AT, AT_OK, DEFAULT_TIMEOUT);
     return ret;
 }
 
@@ -189,14 +190,14 @@ void SIM800::purgeSerial()
 
 void SIM800::write(const char *data)
 {
-    serialSIM800.listen();
+    //serialSIM800.listen();
     serialSIM800.write(data);
 }
 
 void SIM800::write(const char *data, unsigned int size)
 {
-    serialSIM800.listen();
-    serialSIM800.write(data, size);
+    //serialSIM800.listen();
+    serialSIM800.write((const uint8_t*)data, size);
 }
 
 void SIM800::sleep(bool force)
@@ -214,4 +215,5 @@ void SIM800::sleep(bool force)
 void SIM800::wakeUp()
 {
     preInit();
+    sendCmdAndWaitForResp_P(SLEEP_MODE_0, AT_OK, 2000);
 }
diff --git a/src/Sim800.h b/src/Sim800.h
index f699526..9480f73 100644
--- a/src/Sim800.h
+++ b/src/Sim800.h
@@ -30,14 +30,14 @@
 #define __SIM800_H__
 
 #include <Arduino.h>
-#include <SoftwareSerial.h>
+#include <HardwareSerial.h>
 
 #define TRUE 1
 #define FALSE 0
 #define DEFAULT_TIMEOUT 5000
 
 // Comment or uncomment this to debug the library
-// #define DEBUG true
+#define DEBUG true
 
 /** SIM800 class.
  *  Used for SIM800 communication. attention that SIM800 module communicate with MCU in serial protocol
@@ -55,9 +55,9 @@ class SIM800
     SIM800(unsigned int baudRate,
            unsigned int rxPin,
            unsigned int txPin,
-           unsigned int rstPin) : serialSIM800(txPin, rxPin)
+           unsigned int rstPin) : serialSIM800(1)
     {
-        serialSIM800.begin(baudRate);
+        serialSIM800.begin(baudRate, SERIAL_8N1, txPin, rxPin);
         resetPin = rstPin;
     };
 
@@ -139,7 +139,7 @@ class SIM800
     void wakeUp();
 
 protected:
-    SoftwareSerial serialSIM800;
+    HardwareSerial serialSIM800;
     unsigned int resetPin;
 };