diff --git a/freemodbus/common/include/esp_modbus_master.h b/freemodbus/common/include/esp_modbus_master.h
index 9b874a0..d11ade7 100644
--- a/freemodbus/common/include/esp_modbus_master.h
+++ b/freemodbus/common/include/esp_modbus_master.h
@@ -9,6 +9,7 @@
 
 #include <stdint.h>                 // for standard int types definition
 #include <stddef.h>                 // for NULL and std defines
+#include "soc/soc.h"                // for BITN definitions
 #include "esp_modbus_common.h"      // for common types
 
 #ifdef __cplusplus
diff --git a/freemodbus/common/include/esp_modbus_slave.h b/freemodbus/common/include/esp_modbus_slave.h
index 962dbda..7d79b51 100644
--- a/freemodbus/common/include/esp_modbus_slave.h
+++ b/freemodbus/common/include/esp_modbus_slave.h
@@ -10,6 +10,7 @@
 // Public interface header for slave
 #include <stdint.h>                 // for standard int types definition
 #include <stddef.h>                 // for NULL and std defines
+#include "soc/soc.h"                // for BITN definitions
 #include "freertos/FreeRTOS.h"      // for task creation and queues access
 #include "freertos/event_groups.h"  // for event groups
 #include "esp_modbus_common.h"      // for common types
diff --git a/freemodbus/modbus/ascii/mbascii.c b/freemodbus/modbus/ascii/mbascii.c
index 462a641..4400c25 100644
--- a/freemodbus/modbus/ascii/mbascii.c
+++ b/freemodbus/modbus/ascii/mbascii.c
@@ -151,26 +151,33 @@ eMBErrorCode
 eMBASCIIReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )
 {
     eMBErrorCode    eStatus = MB_ENOERR;
+    UCHAR          *pucMBASCIIFrame = ( UCHAR* ) ucASCIIBuf;
+    USHORT          usFrameLength = usRcvBufferPos;
 
+    if( xMBSerialPortGetRequest( &pucMBASCIIFrame, &usFrameLength ) == FALSE )
+    {
+        return MB_EIO;
+    }
+    
     ENTER_CRITICAL_SECTION(  );
-    assert( usRcvBufferPos < MB_SER_PDU_SIZE_MAX );
+    assert( usFrameLength < MB_SER_PDU_SIZE_MAX );
 
     /* Length and CRC check */
-    if( ( usRcvBufferPos >= MB_ASCII_SER_PDU_SIZE_MIN )
-        && ( prvucMBLRC( ( UCHAR * ) ucASCIIBuf, usRcvBufferPos ) == 0 ) )
+   if( ( usFrameLength >= MB_ASCII_SER_PDU_SIZE_MIN )
+        && ( prvucMBLRC( ( UCHAR * ) pucMBASCIIFrame, usFrameLength ) == 0 ) )
     {
         /* Save the address field. All frames are passed to the upper layed
          * and the decision if a frame is used is done there.
          */
-        *pucRcvAddress = ucASCIIBuf[MB_SER_PDU_ADDR_OFF];
+        *pucRcvAddress = pucMBASCIIFrame[MB_SER_PDU_ADDR_OFF];
 
         /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
          * size of address field and CRC checksum.
          */
-        *pusLength = ( USHORT )( usRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_LRC );
+        *pusLength = ( USHORT )( usFrameLength - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_LRC );
 
         /* Return the start of the Modbus PDU to the caller. */
-        *pucFrame = ( UCHAR * ) & ucASCIIBuf[MB_SER_PDU_PDU_OFF];
+        *pucFrame = ( UCHAR * ) & pucMBASCIIFrame[MB_SER_PDU_PDU_OFF];
     }
     else
     {
@@ -186,13 +193,14 @@ eMBASCIISend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )
     eMBErrorCode    eStatus = MB_ENOERR;
     UCHAR           usLRC;
 
-    ENTER_CRITICAL_SECTION(  );
+   
     /* Check if the receiver is still in idle state. If not we where too
      * slow with processing the received frame and the master sent another
      * frame on the network. We have to abort sending the frame.
      */
     if( eRcvState == STATE_RX_IDLE )
     {
+         ENTER_CRITICAL_SECTION(  );
         /* First byte before the Modbus-PDU is the slave address. */
         pucSndBufferCur = ( UCHAR * ) pucFrame - 1;
         usSndBufferCount = 1;
@@ -207,6 +215,13 @@ eMBASCIISend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )
 
         /* Activate the transmitter. */
         eSndState = STATE_TX_START;
+        EXIT_CRITICAL_SECTION(  );
+
+        if ( xMBSerialPortSendResponse( ( UCHAR * ) pucSndBufferCur, usSndBufferCount ) == FALSE )
+        {
+            eStatus = MB_EIO;
+        }
+
         vMBPortSerialEnable( FALSE, TRUE );
     }
     else
diff --git a/freemodbus/modbus/ascii/mbascii_m.c b/freemodbus/modbus/ascii/mbascii_m.c
index 8106598..849ab65 100644
--- a/freemodbus/modbus/ascii/mbascii_m.c
+++ b/freemodbus/modbus/ascii/mbascii_m.c
@@ -154,29 +154,34 @@ eMBErrorCode
 eMBMasterASCIIReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )
 {
     eMBErrorCode    eStatus = MB_ENOERR;
+    UCHAR          *pucMBASCIIFrame = ( UCHAR* ) ucMasterASCIIRcvBuf;
+    USHORT          usFrameLength = usMasterRcvBufferPos;
 
+    if( xMBMasterSerialPortGetResponse( &pucMBASCIIFrame, &usFrameLength ) == FALSE )
+    {
+        return MB_EIO;
+    }
     ENTER_CRITICAL_SECTION(  );
-    assert( usMasterRcvBufferPos < MB_SER_PDU_SIZE_MAX );
+    assert( usFrameLength < MB_SER_PDU_SIZE_MAX );
 
+    assert( pucMBASCIIFrame );
     /* Length and CRC check */
-    if( ( usMasterRcvBufferPos >= MB_ASCII_SER_PDU_SIZE_MIN )
-        && ( prvucMBLRC( ( UCHAR * ) ucMasterASCIIRcvBuf, usMasterRcvBufferPos ) == 0 ) )
+    if( ( usFrameLength >= MB_ASCII_SER_PDU_SIZE_MIN )
+            && ( prvucMBLRC( ( UCHAR * ) pucMBASCIIFrame, usFrameLength ) == 0 ) )
     {
         /* Save the address field. All frames are passed to the upper layed
-         * and the decision if a frame is used is done there.
-         */
-        *pucRcvAddress = ucMasterASCIIRcvBuf[MB_SER_PDU_ADDR_OFF];
+        * and the decision if a frame is used is done there.
+        */
+       *pucRcvAddress = pucMBASCIIFrame[MB_SER_PDU_ADDR_OFF];
 
-        /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
-         * size of address field and CRC checksum.
-         */
-        *pusLength = ( USHORT )( usMasterRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_LRC );
+       /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
+        * size of address field and CRC checksum.
+        */
+       *pusLength = ( USHORT )( usFrameLength - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_LRC );
 
-        /* Return the start of the Modbus PDU to the caller. */
-        *pucFrame = ( UCHAR * ) & ucMasterASCIIRcvBuf[MB_SER_PDU_PDU_OFF];
-    }
-    else
-    {
+       /* Return the start of the Modbus PDU to the caller. */
+       *pucFrame = ( UCHAR * ) & pucMBASCIIFrame[MB_SER_PDU_PDU_OFF];
+   } else {
         eStatus = MB_EIO;
     }
     EXIT_CRITICAL_SECTION(  );
@@ -191,13 +196,13 @@ eMBMasterASCIISend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLengt
 
     if ( ucSlaveAddress > MB_MASTER_TOTAL_SLAVE_NUM ) return MB_EINVAL;
 
-    ENTER_CRITICAL_SECTION(  );
     /* Check if the receiver is still in idle state. If not we where too
      * slow with processing the received frame and the master sent another
      * frame on the network. We have to abort sending the frame.
      */
     if(eRcvState == STATE_M_RX_IDLE)
     {
+        ENTER_CRITICAL_SECTION(  );
         /* First byte before the Modbus-PDU is the slave address. */
         pucMasterSndBufferCur = ( UCHAR * ) pucFrame - 1;
         usMasterSndBufferCount = 1;
@@ -208,17 +213,22 @@ eMBMasterASCIISend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLengt
 
         /* Calculate LRC checksum for Modbus-Serial-Line-PDU. */
         usLRC = prvucMBLRC( ( UCHAR * ) pucMasterSndBufferCur, usMasterSndBufferCount );
-        ucMasterASCIISndBuf[usMasterSndBufferCount++] = usLRC;
+        pucMasterSndBufferCur[usMasterSndBufferCount++] = usLRC;
 
         /* Activate the transmitter. */
         eSndState = STATE_M_TX_START;
+        EXIT_CRITICAL_SECTION(  );
+
+        if ( xMBMasterSerialPortSendRequest( ( UCHAR * ) pucMasterSndBufferCur, usMasterSndBufferCount ) == FALSE )
+        {
+            eStatus = MB_EIO;
+        }
         vMBMasterPortSerialEnable( FALSE, TRUE );
     }
     else
     {
         eStatus = MB_EIO;
     }
-    EXIT_CRITICAL_SECTION(  );
     return eStatus;
 }
 
@@ -447,7 +457,7 @@ xMBMasterASCIITransmitFSM( void )
     return xNeedPoll;
 }
 
-BOOL
+BOOL MB_PORT_ISR_ATTR
 xMBMasterASCIITimerT1SExpired( void )
 {
     BOOL xNeedPoll = FALSE;
@@ -457,7 +467,6 @@ xMBMasterASCIITimerT1SExpired( void )
         /* Timer t35 expired. Startup phase is finished. */
     case STATE_M_RX_INIT:
         xNeedPoll = xMBMasterPortEventPost(EV_MASTER_READY);
-        ESP_EARLY_LOGI("xMBMasterASCIITimerT1SExpired", "RX_INIT_EXPIRED");
         break;
 
         /* Start of message is not received during respond timeout.
diff --git a/freemodbus/modbus/include/mbconfig.h b/freemodbus/modbus/include/mbconfig.h
index 897cc6c..268b748 100644
--- a/freemodbus/modbus/include/mbconfig.h
+++ b/freemodbus/modbus/include/mbconfig.h
@@ -41,6 +41,10 @@
 
 #include "sdkconfig.h" // for KConfig options
 
+#if __has_include("esp_idf_version.h")
+#include "esp_idf_version.h"
+#endif
+
 #ifdef __cplusplus
 PR_BEGIN_EXTERN_C
 #endif
@@ -73,6 +77,15 @@ PR_BEGIN_EXTERN_C
 #error "None of Modbus communication mode is enabled. Please enable one of (ASCII, RTU, TCP) mode in Kconfig."
 #endif
 
+#ifdef ESP_IDF_VERSION
+
+#if (ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(4, 4, 0))
+// Features supported from 4.4
+#define MB_TIMER_SUPPORTS_ISR_DISPATCH_METHOD 1
+#endif
+
+#endif
+
 /*! \brief This option defines the number of data bits per ASCII character.
  *
  * A parity bit is added before the stop bit which keeps the actual byte size at 10 bits.
diff --git a/freemodbus/modbus/include/mbport.h b/freemodbus/modbus/include/mbport.h
index 42773be..acaf908 100644
--- a/freemodbus/modbus/include/mbport.h
+++ b/freemodbus/modbus/include/mbport.h
@@ -145,6 +145,10 @@ BOOL            xMBPortSerialGetByte( CHAR * pucByte );
 
 BOOL            xMBPortSerialPutByte( CHAR ucByte );
 
+BOOL            xMBSerialPortGetRequest( UCHAR **ppucMBSerialFrame, USHORT * pusSerialLength ) __attribute__ ((weak));
+
+BOOL            xMBSerialPortSendResponse( UCHAR *pucMBSerialFrame, USHORT usSerialLength ) __attribute__ ((weak));
+
 #if MB_MASTER_RTU_ENABLED || MB_MASTER_ASCII_ENABLED
 BOOL            xMBMasterPortSerialInit( UCHAR ucPort, ULONG ulBaudRate,
                                    UCHAR ucDataBits, eMBParity eParity );
@@ -158,6 +162,11 @@ void            vMBMasterPortSerialEnable( BOOL xRxEnable, BOOL xTxEnable );
 BOOL            xMBMasterPortSerialGetByte( CHAR * pucByte );
 
 BOOL            xMBMasterPortSerialPutByte( CHAR ucByte );
+
+BOOL            xMBMasterSerialPortGetResponse( UCHAR **ppucMBSerialFrame, USHORT * usSerialLength );
+
+BOOL            xMBMasterSerialPortSendRequest( UCHAR *pucMBSerialFrame, USHORT usSerialLength );
+
 #endif
 
 /* ----------------------- Timers functions ---------------------------------*/
diff --git a/freemodbus/modbus/mb_m.c b/freemodbus/modbus/mb_m.c
index aa5922a..1f13b9a 100644
--- a/freemodbus/modbus/mb_m.c
+++ b/freemodbus/modbus/mb_m.c
@@ -70,18 +70,18 @@
 
 /* ----------------------- Static variables ---------------------------------*/
 
-static UCHAR    ucMBMasterDestAddress;
-static BOOL     xMBRunInMasterMode = FALSE;
+static UCHAR ucMBMasterDestAddress;
+static BOOL xMBRunInMasterMode = FALSE;
 static volatile eMBMasterErrorEventType eMBMasterCurErrorType;
-static volatile USHORT  usMasterSendPDULength;
+static volatile USHORT usMasterSendPDULength;
 static volatile eMBMode eMBMasterCurrentMode;
 
 /*------------------------ Shared variables ---------------------------------*/
 
-volatile UCHAR  ucMasterSndBuf[MB_SERIAL_BUF_SIZE];
-volatile UCHAR  ucMasterRcvBuf[MB_SERIAL_BUF_SIZE];
+volatile UCHAR ucMasterSndBuf[MB_SERIAL_BUF_SIZE];
+volatile UCHAR ucMasterRcvBuf[MB_SERIAL_BUF_SIZE];
 volatile eMBMasterTimerMode eMasterCurTimerMode;
-volatile BOOL   xFrameIsBroadcast = FALSE;
+volatile BOOL xFrameIsBroadcast = FALSE;
 
 static enum
 {
@@ -152,7 +152,7 @@ static xMBFunctionHandler xMasterFuncHandlers[MB_FUNC_HANDLERS_MAX] = {
 };
 
 /* ----------------------- Start implementation -----------------------------*/
-#if MB_MASTER_TCP_ENABLED > 0
+#if MB_MASTER_TCP_ENABLED
 eMBErrorCode
 eMBMasterTCPInit( USHORT ucTCPPort )
 {
diff --git a/freemodbus/modbus/rtu/mbcrc.c b/freemodbus/modbus/rtu/mbcrc.c
index c46e7d1..f413453 100644
--- a/freemodbus/modbus/rtu/mbcrc.c
+++ b/freemodbus/modbus/rtu/mbcrc.c
@@ -39,7 +39,7 @@
 #include "port.h"
 #include "mbconfig.h"
 
-#if MB_MASTER_RTU_ENABLED || MB_SLAVE_RTU_ENABLED
+#if (MB_MASTER_RTU_ENABLED || MB_SLAVE_RTU_ENABLED || CONFIG_MB_UTEST)
 
 static const UCHAR aucCRCHi[] = {
     0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
diff --git a/freemodbus/modbus/rtu/mbrtu.c b/freemodbus/modbus/rtu/mbrtu.c
index 180bde2..144e208 100644
--- a/freemodbus/modbus/rtu/mbrtu.c
+++ b/freemodbus/modbus/rtu/mbrtu.c
@@ -155,26 +155,33 @@ eMBErrorCode
 eMBRTUReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )
 {
     eMBErrorCode    eStatus = MB_ENOERR;
+    UCHAR          *pucMBRTUFrame = ( UCHAR* ) ucRTUBuf;
+    USHORT          usFrameLength = usRcvBufferPos;
+
+    if( xMBSerialPortGetRequest( &pucMBRTUFrame, &usFrameLength ) == FALSE )
+    {
+        return MB_EIO;
+    }
 
     ENTER_CRITICAL_SECTION(  );
-    assert( usRcvBufferPos < MB_SER_PDU_SIZE_MAX );
+    assert( usFrameLength < MB_SER_PDU_SIZE_MAX );
 
     /* Length and CRC check */
-    if( ( usRcvBufferPos >= MB_SER_PDU_SIZE_MIN )
-        && ( usMBCRC16( ( UCHAR * ) ucRTUBuf, usRcvBufferPos ) == 0 ) )
+    if( ( usFrameLength >= MB_SER_PDU_SIZE_MIN )
+        && ( usMBCRC16( ( UCHAR * ) pucMBRTUFrame, usFrameLength ) == 0 ) )
     {
         /* Save the address field. All frames are passed to the upper layed
          * and the decision if a frame is used is done there.
          */
-        *pucRcvAddress = ucRTUBuf[MB_SER_PDU_ADDR_OFF];
+        *pucRcvAddress = pucMBRTUFrame[MB_SER_PDU_ADDR_OFF];
 
         /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
          * size of address field and CRC checksum.
          */
-        *pusLength = ( USHORT )( usRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_CRC );
+        *pusLength = ( USHORT )( usFrameLength - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_CRC );
 
         /* Return the start of the Modbus PDU to the caller. */
-        *pucFrame = ( UCHAR * ) & ucRTUBuf[MB_SER_PDU_PDU_OFF];
+        *pucFrame = ( UCHAR * ) & pucMBRTUFrame[MB_SER_PDU_PDU_OFF];
     }
     else
     {
@@ -191,14 +198,13 @@ eMBRTUSend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )
     eMBErrorCode    eStatus = MB_ENOERR;
     USHORT          usCRC16;
 
-    ENTER_CRITICAL_SECTION(  );
-
     /* Check if the receiver is still in idle state. If not we where to
      * slow with processing the received frame and the master sent another
      * frame on the network. We have to abort sending the frame.
      */
     if( eRcvState == STATE_RX_IDLE )
     {
+        ENTER_CRITICAL_SECTION(  );
         /* First byte before the Modbus-PDU is the slave address. */
         pucSndBufferCur = ( UCHAR * ) pucFrame - 1;
         usSndBufferCount = 1;
@@ -214,13 +220,19 @@ eMBRTUSend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength )
 
         /* Activate the transmitter. */
         eSndState = STATE_TX_XMIT;
+        EXIT_CRITICAL_SECTION(  );
+
+        if( xMBSerialPortSendResponse( ( UCHAR * ) pucSndBufferCur, usSndBufferCount ) == FALSE )
+        {
+            eStatus = MB_EIO;
+        }
+
         vMBPortSerialEnable( FALSE, TRUE );
     }
     else
     {
         eStatus = MB_EIO;
     }
-    EXIT_CRITICAL_SECTION(  );
     return eStatus;
 }
 
@@ -272,7 +284,7 @@ xMBRTUReceiveFSM( void )
     case STATE_RX_RCV:
         if( usRcvBufferPos < MB_SER_PDU_SIZE_MAX )
         {
-            if ( xStatus ) {
+            if( xStatus ) {
                 ucRTUBuf[usRcvBufferPos++] = ucByte;
             }
         }
diff --git a/freemodbus/modbus/rtu/mbrtu_m.c b/freemodbus/modbus/rtu/mbrtu_m.c
index 47a5513..65ac4b7 100644
--- a/freemodbus/modbus/rtu/mbrtu_m.c
+++ b/freemodbus/modbus/rtu/mbrtu_m.c
@@ -161,26 +161,34 @@ eMBErrorCode
 eMBMasterRTUReceive( UCHAR * pucRcvAddress, UCHAR ** pucFrame, USHORT * pusLength )
 {
     eMBErrorCode    eStatus = MB_ENOERR;
+    UCHAR          *pucMBRTUFrame = ( UCHAR* ) ucMasterRTURcvBuf;
+    USHORT          usFrameLength = usMasterRcvBufferPos;
+
+    if( xMBMasterSerialPortGetResponse( &pucMBRTUFrame, &usFrameLength ) == FALSE )
+    {
+        return MB_EIO;
+    }
 
     ENTER_CRITICAL_SECTION(  );
-    assert( usMasterRcvBufferPos < MB_SER_PDU_SIZE_MAX );
+    assert( usFrameLength < MB_SER_PDU_SIZE_MAX );
+    assert( pucMBRTUFrame );
 
     /* Length and CRC check */
-    if( ( usMasterRcvBufferPos >= MB_RTU_SER_PDU_SIZE_MIN )
-        && ( usMBCRC16( ( UCHAR * ) ucMasterRTURcvBuf, usMasterRcvBufferPos ) == 0 ) )
+    if( ( usFrameLength >= MB_RTU_SER_PDU_SIZE_MIN )
+        && ( usMBCRC16( ( UCHAR * ) pucMBRTUFrame, usFrameLength ) == 0 ) )
     {
-        /* Save the address field. All frames are passed to the upper layed
+        /* Save the address field. All frames are passed to the upper layer
          * and the decision if a frame is used is done there.
          */
-        *pucRcvAddress = ucMasterRTURcvBuf[MB_SER_PDU_ADDR_OFF];
+        *pucRcvAddress = pucMBRTUFrame[MB_SER_PDU_ADDR_OFF];
 
         /* Total length of Modbus-PDU is Modbus-Serial-Line-PDU minus
          * size of address field and CRC checksum.
          */
-        *pusLength = ( USHORT )( usMasterRcvBufferPos - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_CRC );
+        *pusLength = ( USHORT )( usFrameLength - MB_SER_PDU_PDU_OFF - MB_SER_PDU_SIZE_CRC );
 
         /* Return the start of the Modbus PDU to the caller. */
-        *pucFrame = ( UCHAR * ) & ucMasterRTURcvBuf[MB_SER_PDU_PDU_OFF];
+        *pucFrame = ( UCHAR * ) & pucMBRTUFrame[MB_SER_PDU_PDU_OFF];
     }
     else
     {
@@ -199,14 +207,13 @@ eMBMasterRTUSend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength
 
     if ( ucSlaveAddress > MB_MASTER_TOTAL_SLAVE_NUM ) return MB_EINVAL;
 
-    ENTER_CRITICAL_SECTION(  );
-
     /* Check if the receiver is still in idle state. If not we where to
      * slow with processing the received frame and the master sent another
      * frame on the network. We have to abort sending the frame.
      */
     if( eRcvState == STATE_M_RX_IDLE )
     {
+        ENTER_CRITICAL_SECTION(  );
         /* First byte before the Modbus-PDU is the slave address. */
         pucMasterSndBufferCur = ( UCHAR * ) pucFrame - 1;
         usMasterSndBufferCount = 1;
@@ -217,11 +224,18 @@ eMBMasterRTUSend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength
 
         /* Calculate CRC16 checksum for Modbus-Serial-Line-PDU. */
         usCRC16 = usMBCRC16( ( UCHAR * ) pucMasterSndBufferCur, usMasterSndBufferCount );
-        ucMasterRTUSndBuf[usMasterSndBufferCount++] = ( UCHAR )( usCRC16 & 0xFF );
-        ucMasterRTUSndBuf[usMasterSndBufferCount++] = ( UCHAR )( usCRC16 >> 8 );
+        pucMasterSndBufferCur[usMasterSndBufferCount++] = ( UCHAR )( usCRC16 & 0xFF );
+        pucMasterSndBufferCur[usMasterSndBufferCount++] = ( UCHAR )( usCRC16 >> 8 );
+        EXIT_CRITICAL_SECTION(  );
 
         /* Activate the transmitter. */
         eSndState = STATE_M_TX_XMIT;
+        
+        if ( xMBMasterSerialPortSendRequest( ( UCHAR * ) pucMasterSndBufferCur, usMasterSndBufferCount ) == FALSE )
+        {
+            eStatus = MB_EIO;
+        }
+        
         // The place to enable RS485 driver
         vMBMasterPortSerialEnable( FALSE, TRUE );
     }
@@ -229,7 +243,6 @@ eMBMasterRTUSend( UCHAR ucSlaveAddress, const UCHAR * pucFrame, USHORT usLength
     {
         eStatus = MB_EIO;
     }
-    EXIT_CRITICAL_SECTION(  );
     return eStatus;
 }
 
@@ -273,11 +286,15 @@ xMBMasterRTUReceiveFSM( void )
         eSndState = STATE_M_TX_IDLE;
 
         usMasterRcvBufferPos = 0;
-        ucMasterRTURcvBuf[usMasterRcvBufferPos++] = ucByte;
-        eRcvState = STATE_M_RX_RCV;
+        if( xStatus && ucByte ) {
+            ucMasterRTURcvBuf[usMasterRcvBufferPos++] = ucByte;
+            eRcvState = STATE_M_RX_RCV;
+        }
 
         /* Enable t3.5 timers. */
+#if CONFIG_FMB_TIMER_PORT_ENABLED
         vMBMasterPortTimersT35Enable( );
+#endif
         break;
 
         /* We are currently receiving a frame. Reset the timer after
@@ -296,7 +313,9 @@ xMBMasterRTUReceiveFSM( void )
         {
             eRcvState = STATE_M_RX_ERROR;
         }
+#if CONFIG_FMB_TIMER_PORT_ENABLED
         vMBMasterPortTimersT35Enable( );
+#endif
         break;
     }
     return xStatus;
diff --git a/freemodbus/port/port.c b/freemodbus/port/port.c
index 1959104..4f672a9 100644
--- a/freemodbus/port/port.c
+++ b/freemodbus/port/port.c
@@ -38,6 +38,7 @@
 
 /* ----------------------- Modbus includes ----------------------------------*/
 #include "freertos/FreeRTOS.h"
+#include "freertos/queue.h"
 #include "sys/lock.h"
 #include "port.h"
 
@@ -72,6 +73,13 @@ vMBPortSetMode( UCHAR ucMode )
     EXIT_CRITICAL_SECTION();
 }
 
+BOOL xMBPortSerialWaitEvent(QueueHandle_t xMbUartQueue, uart_event_t* pxEvent, ULONG xTimeout)
+{
+    BOOL xResult = (BaseType_t)xQueueReceive(xMbUartQueue, (void*)pxEvent, (TickType_t) xTimeout);
+    ESP_LOGD(__func__, "UART event: %d ", pxEvent->type);
+    return xResult;
+}
+
 #if MB_TCP_DEBUG
 
 // This function is kept to realize legacy freemodbus frame logging functionality
diff --git a/freemodbus/port/port.h b/freemodbus/port/port.h
index 42ae780..b5d8858 100644
--- a/freemodbus/port/port.h
+++ b/freemodbus/port/port.h
@@ -38,8 +38,18 @@
 #define PORT_COMMON_H_
 
 #include "freertos/FreeRTOS.h"
+#include "freertos/queue.h"         // for queue
+
 #include "esp_log.h"                // for ESP_LOGE macro
 #include "esp_timer.h"
+#include "driver/uart.h"            // for uart_event_t
+
+#if __has_include("driver/gptimer.h")
+#include "driver/gptimer.h"
+#else
+#include "driver/timer.h"
+#endif
+
 #include "mbconfig.h"
 
 #define INLINE                      inline
@@ -174,6 +184,8 @@ void prvvMBTCPLogFrame( const CHAR * pucMsg, UCHAR * pucFrame, USHORT usFrameLen
 void vMBPortSetMode( UCHAR ucMode );
 UCHAR ucMBPortGetMode( void );
 
+BOOL xMBPortSerialWaitEvent(QueueHandle_t xMbUartQueue, uart_event_t* pxEvent, ULONG xTimeout);
+
 #ifdef __cplusplus
 PR_END_EXTERN_C
 #endif /* __cplusplus */
diff --git a/freemodbus/port/portserial.c b/freemodbus/port/portserial.c
index a57a6c6..aae45d9 100644
--- a/freemodbus/port/portserial.c
+++ b/freemodbus/port/portserial.c
@@ -33,6 +33,8 @@
  *
  * File: $Id: portother.c,v 1.1 2010/06/06 13:07:20 wolti Exp $
  */
+
+#include "driver/uart.h"
 #include "port.h"
 #include "driver/uart.h"
 #include "freertos/queue.h" // for queue support
@@ -85,15 +87,14 @@ static USHORT usMBPortSerialRxPoll(size_t xEventSize)
 
     if (bRxStateEnabled) {
         // Get received packet into Rx buffer
-        while(xReadStatus && (usCnt++ <= MB_SERIAL_BUF_SIZE)) {
+        while(xReadStatus && (usCnt++ <= xEventSize)) {
             // Call the Modbus stack callback function and let it fill the buffers.
             xReadStatus = pxMBFrameCBByteReceived(); // callback to execute receive FSM
         }
         uart_flush_input(ucUartNumber);
         // Send event EV_FRAME_RECEIVED to allow stack process packet
 #if !CONFIG_FMB_TIMER_PORT_ENABLED
-        // Let the stack know that T3.5 time is expired and data is received
-        (void)pxMBPortCBTimerExpired(); // calls callback xMBRTUTimerT35Expired();
+        pxMBPortCBTimerExpired();
 #endif
         ESP_LOGD(TAG, "RX: %d bytes\n", usCnt);
     }
@@ -126,7 +127,7 @@ static void vUartTask(void *pvParameters)
     uart_event_t xEvent;
     USHORT usResult = 0;
     for(;;) {
-        if (xQueueReceive(xMbUartQueue, (void*)&xEvent, portMAX_DELAY) == pdTRUE) {
+        if (xMBPortSerialWaitEvent(xMbUartQueue, (void*)&xEvent, portMAX_DELAY)) {
             ESP_LOGD(TAG, "MB_uart[%d] event:", ucUartNumber);
             switch(xEvent.type) {
                 //Event of UART receving data
@@ -135,6 +136,8 @@ static void vUartTask(void *pvParameters)
                     // This flag set in the event means that no more
                     // data received during configured timeout and UART TOUT feature is triggered
                     if (xEvent.timeout_flag) {
+                        // Get buffered data length
+                        ESP_ERROR_CHECK(uart_get_buffered_data_len(ucUartNumber, &xEvent.size));
                         // Read received data and send it to modbus stack
                         usResult = usMBPortSerialRxPoll(xEvent.size);
                         ESP_LOGD(TAG,"Timeout occured, processed: %d bytes", usResult);
@@ -219,7 +222,7 @@ BOOL xMBPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate,
         .stop_bits = UART_STOP_BITS_1,
         .flow_ctrl = UART_HW_FLOWCTRL_DISABLE,
         .rx_flow_ctrl_thresh = 2,
-        .source_clk = UART_SCLK_APB,
+        .source_clk = UART_SCLK_APB
     };
     // Set UART config
     xErr = uart_param_config(ucUartNumber, &xUartConfig);
@@ -257,6 +260,17 @@ BOOL xMBPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate,
     return TRUE;
 }
 
+BOOL xMBSerialPortGetRequest( UCHAR **ppucMBSerialFrame, USHORT * usSerialLength )
+{
+    BOOL eStatus = TRUE;
+    return eStatus;
+}
+
+BOOL xMBSerialPortSendResponse( UCHAR *pucMBSerialFrame, USHORT usSerialLength )
+{
+    return TRUE;
+}
+
 void vMBPortSerialClose(void)
 {
     (void)vTaskSuspend(xMbTaskHandle);
diff --git a/freemodbus/port/portserial_m.c b/freemodbus/port/portserial_m.c
index b0324e3..777eee8 100644
--- a/freemodbus/port/portserial_m.c
+++ b/freemodbus/port/portserial_m.c
@@ -89,7 +89,7 @@ static USHORT usMBMasterPortSerialRxPoll(size_t xEventSize)
     USHORT usCnt = 0;
 
     if (bRxStateEnabled) {
-        while(xReadStatus && (usCnt++ <= MB_SERIAL_BUF_SIZE)) {
+        while(xReadStatus && (usCnt++ <= xEventSize)) {
             // Call the Modbus stack callback function and let it fill the stack buffers.
             xReadStatus = pxMBMasterFrameCBByteReceived(); // callback to receive FSM
         }
@@ -134,7 +134,7 @@ static void vUartTask(void* pvParameters)
     uart_event_t xEvent;
     USHORT usResult = 0;
     for(;;) {
-        if (xQueueReceive(xMbUartQueue, (void*)&xEvent, portMAX_DELAY) == pdTRUE) {
+        if (xMBPortSerialWaitEvent(xMbUartQueue, (void*)&xEvent, portMAX_DELAY)) {
             ESP_LOGD(TAG, "MB_uart[%d] event:", ucUartNumber);
             switch(xEvent.type) {
                 //Event of UART receiving data
@@ -143,6 +143,8 @@ static void vUartTask(void* pvParameters)
                     // This flag set in the event means that no more
                     // data received during configured timeout and UART TOUT feature is triggered
                     if (xEvent.timeout_flag) {
+                        // Get buffered data length
+                        ESP_ERROR_CHECK(uart_get_buffered_data_len(ucUartNumber, &xEvent.size));
                         // Read received data and send it to modbus stack
                         usResult = usMBMasterPortSerialRxPoll(xEvent.size);
                         ESP_LOGD(TAG,"Timeout occured, processed: %d bytes", usResult);
@@ -266,6 +268,24 @@ BOOL xMBMasterPortSerialInit( UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
     return TRUE;
 }
 
+/*
+ * The function is called from ASCII/RTU module to get processed data buffer. Sets the
+ * received buffer and its length using parameters.
+ */
+BOOL xMBMasterSerialPortGetResponse( UCHAR **ppucMBSerialFrame, USHORT * usSerialLength )
+{
+    return TRUE;
+}
+
+/*
+ * The function is called from ASCII/RTU module to set processed data buffer
+ * to be sent in transmitter state machine.
+ */
+BOOL xMBMasterSerialPortSendRequest( UCHAR *pucMBSerialFrame, USHORT usSerialLength )
+{
+    return TRUE;
+}
+
 void vMBMasterPortSerialClose(void)
 {
     (void)vTaskDelete(xMbTaskHandle);
diff --git a/freemodbus/port/porttimer.c b/freemodbus/port/porttimer.c
index 9e2673f..4fbfbfd 100644
--- a/freemodbus/port/porttimer.c
+++ b/freemodbus/port/porttimer.c
@@ -74,7 +74,7 @@ BOOL xMBPortTimersInit(USHORT usTimeOut50us)
     esp_timer_create_args_t xTimerConf = {
         .callback = vTimerAlarmCBHandler,
         .arg = NULL,
-#if CONFIG_FMB_TIMER_USE_ISR_DISPATCH_METHOD
+#if (MB_TIMER_SUPPORTS_ISR_DISPATCH_METHOD && CONFIG_FMB_TIMER_USE_ISR_DISPATCH_METHOD)
         .dispatch_method = ESP_TIMER_ISR,
 #else
         .dispatch_method = ESP_TIMER_TASK,
diff --git a/freemodbus/port/porttimer_m.c b/freemodbus/port/porttimer_m.c
index 3982f27..f1595a6 100644
--- a/freemodbus/port/porttimer_m.c
+++ b/freemodbus/port/porttimer_m.c
@@ -71,7 +71,7 @@ BOOL xMBMasterPortTimersInit(USHORT usTimeOut50us)
     esp_timer_create_args_t xTimerConf = {
         .callback = vTimerAlarmCBHandler,
         .arg = NULL,
-#if CONFIG_FMB_TIMER_USE_ISR_DISPATCH_METHOD
+#if (MB_TIMER_SUPPORTS_ISR_DISPATCH_METHOD && CONFIG_FMB_TIMER_USE_ISR_DISPATCH_METHOD)
         .dispatch_method = ESP_TIMER_ISR,
 #else
         .dispatch_method = ESP_TIMER_TASK,
diff --git a/freemodbus/serial_master/modbus_controller/mbc_serial_master.c b/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
index 3a3f2da..94bec3f 100644
--- a/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
+++ b/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
@@ -30,7 +30,7 @@ extern BOOL xMBMasterPortSerialTxPoll(void);
 #define MB_RESPONSE_TICS pdMS_TO_TICKS(CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND + 10)
 
 
-static mb_master_interface_t* mbm_interface_ptr = NULL; //&default_interface_inst;
+static mb_master_interface_t* mbm_interface_ptr = NULL;
 static const char *TAG = "MB_CONTROLLER_MASTER";
 
 // Modbus event processing task
@@ -101,7 +101,7 @@ static esp_err_t mbc_serial_master_start(void)
             "mb stack initialization failure, eMBInit() returns (0x%x).", status);
     status = eMBMasterEnable();
     MB_MASTER_CHECK((status == MB_ENOERR), ESP_ERR_INVALID_STATE,
-            "mb stack set slave ID failure, eMBEnable() returned (0x%x).", (uint32_t)status);
+            "mb stack set slave ID failure, eMBMasterEnable() returned (0x%x).", (uint32_t)status);
     // Set the mbcontroller start flag
     EventBits_t flag = xEventGroupSetBits(mbm_opts->mbm_event_group,
                                             (EventBits_t)MB_EVENT_STACK_STARTED);
diff --git a/freemodbus/tcp_master/modbus_controller/mbc_tcp_master.c b/freemodbus/tcp_master/modbus_controller/mbc_tcp_master.c
index bdcfe14..f1f3916 100644
--- a/freemodbus/tcp_master/modbus_controller/mbc_tcp_master.c
+++ b/freemodbus/tcp_master/modbus_controller/mbc_tcp_master.c
@@ -159,7 +159,7 @@ static esp_err_t mbc_tcp_master_start(void)
 
     status = eMBMasterEnable();
     MB_MASTER_CHECK((status == MB_ENOERR), ESP_ERR_INVALID_STATE,
-                    "mb stack set slave ID failure, eMBMasterEnable() returned (0x%x).", (uint32_t)status);
+                    "mb stack enable failure, eMBMasterEnable() returned (0x%x).", (uint32_t)status);
 
     // Add slave IP address for each slave to initialize connection
     mb_slave_addr_entry_t *p_slave_info;
@@ -172,13 +172,12 @@ static esp_err_t mbc_tcp_master_start(void)
     // Add end of list condition
     (void)xMBTCPPortMasterAddSlaveIp(0xFF, NULL, 0xFF);
 
-
     // Wait for connection done event
     bool start = (bool)xMBTCPPortMasterWaitEvent(mbm_opts->mbm_event_group,
-                                                 (EventBits_t)MB_EVENT_STACK_STARTED, MB_TCP_CONNECTION_TOUT);
+                                                    (EventBits_t)MB_EVENT_STACK_STARTED, MB_TCP_CONNECTION_TOUT);
     MB_MASTER_CHECK((start), ESP_ERR_INVALID_STATE,
-                    "mb stack could not connect to slaves for %d seconds.",
-                    CONFIG_FMB_TCP_CONNECTION_TOUT_SEC);
+                            "mb stack could not connect to slaves for %d seconds.",
+                            CONFIG_FMB_TCP_CONNECTION_TOUT_SEC);
     return ESP_OK;
 }
 
diff --git a/freemodbus/tcp_slave/port/port_tcp_slave.c b/freemodbus/tcp_slave/port/port_tcp_slave.c
index e7046d6..c5eee09 100644
--- a/freemodbus/tcp_slave/port/port_tcp_slave.c
+++ b/freemodbus/tcp_slave/port/port_tcp_slave.c
@@ -560,6 +560,12 @@ static void vMBTCPPortServerTask(void *pvParameters)
                                                                             pxClientInfo->xSockId, pxClientInfo->pcIpAddr, xErr);
                                         break;
                                 }
+                                
+                                if (xShutdownSemaphore) {
+                                    xSemaphoreGive(xShutdownSemaphore);
+                                    vTaskDelete(NULL);
+                                }
+
                                 // Close client connection
                                 xMBTCPPortCloseConnection(pxClientInfo);
 
diff --git a/idf_component.yml b/idf_component.yml
index 6af0316..a9cfdef 100644
--- a/idf_component.yml
+++ b/idf_component.yml
@@ -1,5 +1,10 @@
-version: "0.1.0"
+version: "0.0.2"
 description: ESP-MODBUS is the official Modbus library for Espressif SoCs.
 dependencies:
   idf: ">=4.1"
-
+files:
+  exclude:
+    - "docs/_build/**/*"
+    - "docs/_build"
+    - "test/**/build/**/*"
+    - "test/**/build"
diff --git a/test/README.md b/test/README.md
index eef0cb2..e8931d4 100644
--- a/test/README.md
+++ b/test/README.md
@@ -1,7 +1,9 @@
-# Test Apps
+# Test implementation
 
 This directory contains a set of ESP-IDF projects to be used as tests only, which aim to exercise various
 configuration of components to check completely arbitrary functionality should it be building only, executing under
 various conditions or combination with other components, including custom test frameworks.
 
-The test apps are not intended to demonstrate the ESP-IDF functionality in any way.
+The tests in this folder are not intended to demonstrate the ESP-IDF functionality in any way.
+
+The examples can be found here: https://github.com/espressif/esp-idf/tree/master/examples/protocols/modbus
diff --git a/test/mb_example_common/CMakeLists.txt b/test/mb_example_common/CMakeLists.txt
index bbd076e..c4854e9 100644
--- a/test/mb_example_common/CMakeLists.txt
+++ b/test/mb_example_common/CMakeLists.txt
@@ -2,5 +2,4 @@
 # CMakeLists in this exact order for cmake to work correctly
 cmake_minimum_required(VERSION 3.5)
 idf_component_register(SRCS "modbus_params.c"
-                    INCLUDE_DIRS "include"
-                    PRIV_REQUIRES esp-modbus)
+                    INCLUDE_DIRS "include")
diff --git a/test/serial/mb_serial_master/sdkconfig.defaults b/test/serial/mb_serial_master/sdkconfig.defaults
index 4773f5b..3c9c6de 100644
--- a/test/serial/mb_serial_master/sdkconfig.defaults
+++ b/test/serial/mb_serial_master/sdkconfig.defaults
@@ -3,10 +3,8 @@
 #
 CONFIG_MB_COMM_MODE_ASCII=y
 CONFIG_MB_UART_BAUD_RATE=115200
-CONFIG_FMB_TIMER_PORT_ENABLED=y
-CONFIG_FMB_TIMER_GROUP=0
-CONFIG_FMB_TIMER_INDEX=0
+CONFIG_FMB_TIMER_PORT_ENABLED=n
 CONFIG_FMB_TIMER_ISR_IN_IRAM=y
 CONFIG_FMB_MASTER_DELAY_MS_CONVERT=200
-CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND=150
+CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND=400
 CONFIG_FMB_TIMER_USE_ISR_DISPATCH_METHOD=y
diff --git a/test/serial/mb_serial_slave/dependencies.lock b/test/serial/mb_serial_slave/dependencies.lock
deleted file mode 100644
index ce2bede..0000000
--- a/test/serial/mb_serial_slave/dependencies.lock
+++ /dev/null
@@ -1,9 +0,0 @@
-dependencies:
-  idf:
-    component_hash: null
-    source:
-      type: idf
-    version: 5.0.0
-manifest_hash: ef92ef397dcb09fa7a851b483306296fee18dfca839e1a68e8190dad2ed66a64
-target: esp32
-version: 1.0.0
diff --git a/test/serial/mb_serial_slave/sdkconfig.defaults b/test/serial/mb_serial_slave/sdkconfig.defaults
index 6507dfa..14806eb 100644
--- a/test/serial/mb_serial_slave/sdkconfig.defaults
+++ b/test/serial/mb_serial_slave/sdkconfig.defaults
@@ -4,8 +4,6 @@
 CONFIG_MB_COMM_MODE_ASCII=y
 CONFIG_MB_SLAVE_ADDR=1
 CONFIG_MB_UART_BAUD_RATE=115200
-CONFIG_FMB_TIMER_PORT_ENABLED=y
-CONFIG_FMB_TIMER_GROUP=0
-CONFIG_FMB_TIMER_INDEX=0
+CONFIG_FMB_TIMER_PORT_ENABLED=n
 CONFIG_FMB_TIMER_ISR_IN_IRAM=y
 CONFIG_FMB_TIMER_USE_ISR_DISPATCH_METHOD=y