diff --git a/mcp_can.cpp b/mcp_can.cpp
index e66a4bc..f42dc08 100644
--- a/mcp_can.cpp
+++ b/mcp_can.cpp
@@ -106,7 +106,7 @@ void MCP_CAN::mcp2515_readRegisterS(const byte address, byte values[], const byt
     spi_readwrite(MCP_READ);
     spi_readwrite(address);
     // mcp2515 has auto-increment of address-pointer
-    for(i=0; i<n && i<CAN_MAX_CHAR_IN_MESSAGE; i++) 
+    for(i=0; i<n && i<CAN_MAX_CHAR_IN_MESSAGE; i++)
     {
         values[i] = spi_read();
     }
@@ -367,7 +367,7 @@ void MCP_CAN::mcp2515_initCANBuffers(void)
     a2 = MCP_TXB1CTRL;
     a3 = MCP_TXB2CTRL;
     for(i = 0; i < 14; i++)                         // in-buffer loop
-    {                                           
+    {
         mcp2515_setRegister(a1, 0);
         mcp2515_setRegister(a2, 0);
         mcp2515_setRegister(a3, 0);
@@ -529,12 +529,14 @@ void MCP_CAN::mcp2515_read_id(const byte mcp_addr, byte* ext, unsigned long* id)
 ** Function name:           mcp2515_write_canMsg
 ** Descriptions:            write msg
 *********************************************************************************************************/
-void MCP_CAN::mcp2515_write_canMsg(const byte buffer_sidh_addr)
+void MCP_CAN::mcp2515_write_canMsg(const byte buffer_sidh_addr, int rtrBit)
 {
     byte mcp_addr;
     mcp_addr = buffer_sidh_addr;
     mcp2515_setRegisterS(mcp_addr+5, dta, dta_len);                  // write data bytes
-    if(rtr == 1)                                                   // if RTR set bit in byte
+    // Serial.print("RTR: ");
+    // Serial.println(rtrBit);
+    if(rtrBit == 1)                                                   // if RTR set bit in byte
     {
         dta_len |= MCP_RTR_MASK;
     }
@@ -584,7 +586,7 @@ byte MCP_CAN::mcp2515_getNextFreeTXBuf(byte *txbuf_n)                 // get Nex
     *txbuf_n = 0x00;
 
     // check all 3 TX-Buffers
-    for(i=0; i<MCP_N_TXBUFFERS; i++) 
+    for(i=0; i<MCP_N_TXBUFFERS; i++)
     {
         ctrlval = mcp2515_readRegister(ctrlregs[i]);
         if((ctrlval & MCP_TXB_TXREQ_M) == 0) {
@@ -776,7 +778,7 @@ byte MCP_CAN::clearMsg()
     ext_flg     = 0;
     rtr         = 0;
     filhit      = 0;
-    
+
     for(int i = 0; i<dta_len; i++)
     {
         dta[i] = 0x00;
@@ -789,7 +791,7 @@ byte MCP_CAN::clearMsg()
 ** Function name:           sendMsg
 ** Descriptions:            send message
 *********************************************************************************************************/
-byte MCP_CAN::sendMsg()
+byte MCP_CAN::sendMsg(int rtrBit)
 {
     byte res, res1, txbuf_n;
     uint16_t uiTimeOut = 0;
@@ -803,23 +805,23 @@ byte MCP_CAN::sendMsg()
     {
         return CAN_GETTXBFTIMEOUT;                                      // get tx buff time out
     }
-    
+
     uiTimeOut = 0;
-    mcp2515_write_canMsg(txbuf_n);
+    mcp2515_write_canMsg(txbuf_n, rtrBit);
     mcp2515_start_transmit(txbuf_n);
-    
+
     do {
         uiTimeOut++;
         res1= mcp2515_readRegister(txbuf_n-1 /* the ctrl reg is located at txbuf_n-1 */);  // read send buff ctrl reg
         res1 = res1 & 0x08;
     }while(res1 && (uiTimeOut < TIMEOUTVALUE));
-    
+
     if(uiTimeOut == TIMEOUTVALUE)                                       // send msg timeout
     {
         return CAN_SENDMSGTIMEOUT;
     }
     return CAN_OK;
-    
+
 }
 
 /*********************************************************************************************************
@@ -829,7 +831,9 @@ byte MCP_CAN::sendMsg()
 byte MCP_CAN::sendMsgBuf(unsigned long id, byte ext, byte rtr, byte len, byte *buf)
 {
     setMsg(id, ext, len, rtr, buf);
-    return sendMsg();
+    // Serial.print("RTR00: ");
+    // Serial.println(rtr, HEX);
+    return sendMsg(rtr);
 }
 
 /*********************************************************************************************************
@@ -839,7 +843,7 @@ byte MCP_CAN::sendMsgBuf(unsigned long id, byte ext, byte rtr, byte len, byte *b
 byte MCP_CAN::sendMsgBuf(unsigned long id, byte ext, byte len, byte *buf)
 {
     setMsg(id, ext, len, buf);
-    return sendMsg();
+    return sendMsg(0);
 }
 
 
@@ -884,7 +888,7 @@ byte MCP_CAN::readMsgBuf(byte *len, byte buf[])
 
     if(rc == CAN_OK) {
         *len = dta_len;
-        for(int i = 0; i<dta_len; i++) 
+        for(int i = 0; i<dta_len; i++)
         {
             buf[i] = dta[i];
         }
@@ -898,7 +902,7 @@ byte MCP_CAN::readMsgBuf(byte *len, byte buf[])
 ** Function name:           readMsgBufID
 ** Descriptions:            read message buf and can bus source ID
 *********************************************************************************************************/
-byte MCP_CAN::readMsgBufID(unsigned long *ID, byte *len, byte buf[])
+byte MCP_CAN::readMsgBufID(byte *ID, byte *len, byte buf[])
 {
     byte rc;
     rc = readMsg();
@@ -906,7 +910,7 @@ byte MCP_CAN::readMsgBufID(unsigned long *ID, byte *len, byte buf[])
     if(rc == CAN_OK) {
         *len = dta_len;
         *ID  = can_id;
-        for(int i = 0; i<dta_len && i < MAX_CHAR_IN_MESSAGE; i++) 
+        for(int i = 0; i<dta_len && i < MAX_CHAR_IN_MESSAGE; i++)
         {
             buf[i] = dta[i];
         }
@@ -966,4 +970,4 @@ byte MCP_CAN::isExtendedFrame(void)
 
 /*********************************************************************************************************
   END FILE
-*********************************************************************************************************/
\ No newline at end of file
+*********************************************************************************************************/
diff --git a/mcp_can.h b/mcp_can.h
index 40d92af..7a9bf88 100644
--- a/mcp_can.h
+++ b/mcp_can.h
@@ -4,9 +4,9 @@
 
   Author:Loovee (loovee@seeed.cc)
   2014-1-16
-  
-  Contributor: 
-  
+
+  Contributor:
+
   Cory J. Fowler
   Latonita
   Woodward1
@@ -20,7 +20,7 @@
   Adlerweb
   Btetz
   Hurvajs
-  
+
   The MIT License (MIT)
 
   Copyright (c) 2013 Seeed Technology Inc.
@@ -53,8 +53,8 @@
 class MCP_CAN
 {
     private:
-    
-    byte   ext_flg;                         // identifier xxxID      
+
+    byte   ext_flg;                         // identifier xxxID
                                             // either extended (the 29 LSB) or standard (the 11 LSB)
     unsigned long  can_id;                  // can id
     byte   dta_len;                         // data length
@@ -64,73 +64,73 @@ class MCP_CAN
     byte   SPICS;
 
 /*
-*  mcp2515 driver function 
+*  mcp2515 driver function
 */
 
 private:
 
-    void mcp2515_reset(void);                                   // reset mcp2515                
+    void mcp2515_reset(void);                                   // reset mcp2515
 
-    byte mcp2515_readRegister(const byte address);              // read mcp2515's register      
-    
-    void mcp2515_readRegisterS(const byte address, 
-	                           byte values[], 
+    byte mcp2515_readRegister(const byte address);              // read mcp2515's register
+
+    void mcp2515_readRegisterS(const byte address,
+	                       byte values[],
                                const byte n);
-    void mcp2515_setRegister(const byte address,                // set mcp2515's register       
+    void mcp2515_setRegister(const byte address,                // set mcp2515's register
                              const byte value);
 
-    void mcp2515_setRegisterS(const byte address,               // set mcp2515's registers      
+    void mcp2515_setRegisterS(const byte address,               // set mcp2515's registers
                               const byte values[],
                               const byte n);
-    
+
     void mcp2515_initCANBuffers(void);
-    
-    void mcp2515_modifyRegister(const byte address,             // set bit of one register      
+
+    void mcp2515_modifyRegister(const byte address,             // set bit of one register
                                 const byte mask,
                                 const byte data);
 
-    byte mcp2515_readStatus(void);                              // read mcp2515's Status        
-    byte mcp2515_setCANCTRL_Mode(const byte newmode);           // set mode                     
-    byte mcp2515_configRate(const byte canSpeed);               // set boadrate                 
-    byte mcp2515_init(const byte canSpeed);                     // mcp2515init                  
+    byte mcp2515_readStatus(void);                              // read mcp2515's Status
+    byte mcp2515_setCANCTRL_Mode(const byte newmode);           // set mode
+    byte mcp2515_configRate(const byte canSpeed);               // set boadrate
+    byte mcp2515_init(const byte canSpeed);                     // mcp2515init
 
-    void mcp2515_write_id(const byte mcp_addr,                 // write can id                 
-                           const byte ext,
-                           const unsigned long id);
+    void mcp2515_write_id( const byte mcp_addr,                 // write can id
+                               const byte ext,
+                               const unsigned long id );
 
-    void mcp2515_read_id(const byte mcp_addr,                  // read can id                  
-                          byte* ext,
-                          unsigned long* id);
+    void mcp2515_read_id( const byte mcp_addr,                  // read can id
+                                    byte* ext,
+                                    unsigned long* id );
 
-    void mcp2515_write_canMsg(const byte buffer_sidh_addr);   // write can msg                
-    void mcp2515_read_canMsg(const byte buffer_sidh_addr);     // read can msg                 
-    void mcp2515_start_transmit(const byte mcp_addr);           // start transmit               
-    byte mcp2515_getNextFreeTXBuf(byte *txbuf_n);               // get Next free txbuf          
+    void mcp2515_write_canMsg( const byte buffer_sidh_addr, int rtrBit );   // write can msg
+    void mcp2515_read_canMsg( const byte buffer_sidh_addr);     // read can msg
+    void mcp2515_start_transmit(const byte mcp_addr);           // start transmit
+    byte mcp2515_getNextFreeTXBuf(byte *txbuf_n);               // get Next free txbuf
 
 /*
 *  can operator function
-*/    
+*/
 
-    byte setMsg(unsigned long id, byte ext, byte len, byte rtr, byte *pData);   // set message                    
-    byte setMsg(unsigned long id, byte ext, byte len, byte *pData);             //  set message                    
-    byte clearMsg();                                                // clear all message to zero    
-    byte readMsg();                                                 // read message                 
-    byte sendMsg();                                                 // send message                 
+    byte setMsg(unsigned long id, byte ext, byte len, byte rtr, byte *pData);   // set message
+    byte setMsg(unsigned long id, byte ext, byte len, byte *pData);             //  set message
+    byte clearMsg();                                                // clear all message to zero
+    byte readMsg();                                                 // read message
+    byte sendMsg(int rtrBit);                                                 // send message
 
 public:
     MCP_CAN(byte _CS);
-    byte begin(byte speedset);                                      // init can                     
-    byte init_Mask(byte num, byte ext, unsigned long ulData);       // init Masks                   
-    byte init_Filt(byte num, byte ext, unsigned long ulData);       // init filters                 
-    byte sendMsgBuf(unsigned long id, byte ext, byte rtr, byte len, byte *buf);     // send buf                     
-    byte sendMsgBuf(unsigned long id, byte ext, byte len, byte *buf);               // send buf                     
-    byte readMsgBuf(byte *len, byte *buf);                          // read buf                     
-    byte readMsgBufID(unsigned long *ID, byte *len, byte *buf);     // read buf with object ID      
-    byte checkReceive(void);                                        // if something received        
-    byte checkError(void);                                          // if something error           
-    unsigned long getCanId(void);                                   // get can id when receive      
-    byte isRemoteRequest(void);                                     // get RR flag when receive     
-    byte isExtendedFrame(void);                                     // did we recieve 29bit frame?  
+    byte begin(byte speedset);                                      // init can
+    byte init_Mask(byte num, byte ext, unsigned long ulData);       // init Masks
+    byte init_Filt(byte num, byte ext, unsigned long ulData);       // init filters
+    byte sendMsgBuf(unsigned long id, byte ext, byte rtr, byte len, byte *buf);     // send buf
+    byte sendMsgBuf(unsigned long id, byte ext, byte len, byte *buf);               // send buf
+    byte readMsgBuf(byte *len, byte *buf);                          // read buf
+    byte readMsgBufID(byte *ID, byte *len, byte *buf);     // read buf with object ID
+    byte checkReceive(void);                                        // if something received
+    byte checkError(void);                                          // if something error
+    unsigned long getCanId(void);                                   // get can id when receive
+    byte isRemoteRequest(void);                                     // get RR flag when receive
+    byte isExtendedFrame(void);                                     // did we recieve 29bit frame?
 };
 
 #endif