Patch to add the windowing support in the libnfc

This patch enables windowing of LLC packets send from chipset to host.
The host will now wait for up to 4 LLC packets from the chipset before
sending an ACK (S-Frame RR).

Change-Id: I6a70e1d780847a104e3ec8e403593a69e222aec9

8 files changed, 340 insertions, 196 deletions

diff --git a/inc/phNfcConfig.h b/inc/phNfcConfig.h
index c234724..e7386d9 100644
--- a/inc/phNfcConfig.h
+++ b/inc/phNfcConfig.h
@@ -223,6 +223,12 @@
 #define LINK_CONNECTION_TIMEOUT         1000U
 #endif 
 
+/**< Defines ACK time out value for LLC timer,
+    150 is in milliseconds */
+#ifndef LINK_ACK_TIMEOUT
+#define LINK_ACK_TIMEOUT                1U
+#endif
+
 
 /**< Defines Firmware Download Completion Timeout value ,
     120000 is in milliseconds */
diff --git a/src/phLlcNfc.c b/src/phLlcNfc.c
index af0a3a1..36b442b 100644
--- a/src/phLlcNfc.c
+++ b/src/phLlcNfc.c
@@ -228,7 +228,7 @@ phLlcNfc_Init (
 {
     NFCSTATUS               result = NFCSTATUS_SUCCESS;
     phLlcNfc_Context_t      *ps_llc_ctxt = (phLlcNfc_Context_t*)pContext;
-    phLlcNfc_LlcPacket_t    *ps_packet_info = NULL;
+    phLlcNfc_LlcPacket_t    s_packet_info;
     
     PH_LLCNFC_PRINT("Llc Init called\n");
     if ((NULL == ps_llc_ctxt) || (NULL == pLinkInfo))
@@ -239,8 +239,6 @@ phLlcNfc_Init (
     else
     {
         /* Initialisation */
-        ps_packet_info = &(ps_llc_ctxt->s_frameinfo.s_llcpacket);
-    
         ps_llc_ctxt->phwinfo = pLinkInfo;
         /* Call the internal frame initialise */
         phLlcNfc_H_Frame_Init(ps_llc_ctxt);
@@ -258,17 +256,17 @@ phLlcNfc_Init (
             phLlcNfc_CreateTimers();               
 
             /* Create a U frame */
-            result = phLlcNfc_H_CreateUFramePayload(ps_llc_ctxt, 
-                                    ps_packet_info, 
-                                    &(ps_packet_info->llcbuf_len), 
+            result = phLlcNfc_H_CreateUFramePayload(ps_llc_ctxt,
+                                    &s_packet_info,
+                                    &(s_packet_info.llcbuf_len),
                                     phLlcNfc_e_rset);
         }
         if (NFCSTATUS_SUCCESS == result)
         {
             /* Call DAL write */
             result = phLlcNfc_Interface_Write(ps_llc_ctxt, 
-                                (uint8_t*)&(ps_packet_info->s_llcbuf), 
-                                (uint32_t)ps_packet_info->llcbuf_len);
+                                (uint8_t*)&(s_packet_info.s_llcbuf),
+                                (uint32_t)s_packet_info.llcbuf_len);
         }
         if (NFCSTATUS_PENDING == result)
         {
@@ -364,8 +362,7 @@ phLlcNfc_Send (
     NFCSTATUS               result = NFCSTATUS_SUCCESS;
     phLlcNfc_Context_t      *ps_llc_ctxt = (phLlcNfc_Context_t*)pContext;
     phLlcNfc_Frame_t        *ps_frame_info = NULL;
-    phLlcNfc_LlcPacket_t    *ps_packet_info = NULL, 
-                            s_packet_info;
+    phLlcNfc_LlcPacket_t    s_packet_info;
     phLlcNfc_StoreIFrame_t  *ps_store_frame = NULL;
 #if 0
     uint8_t                 count = 1;
@@ -404,7 +401,6 @@ phLlcNfc_Send (
                                 &s_packet_info, 
                                 pLlcBuf, (uint8_t)llcBufLength);
 
-        ps_packet_info = &(ps_frame_info->s_llcpacket);
 
         /* Store the I frame in the send list */
         (void)phLlcNfc_H_StoreIFrame (ps_store_frame, s_packet_info);
@@ -423,13 +419,11 @@ phLlcNfc_Send (
 
 #endif /* #ifdef CTRL_WIN_SIZE_COUNT */
         {
-            (void)memcpy ((void *)ps_packet_info, (void *)&s_packet_info, 
-                        sizeof(phLlcNfc_LlcPacket_t));
             /* Call write to the below layer, only if previous write 
                 is completed */
             result = phLlcNfc_Interface_Write (ps_llc_ctxt, 
-                                (uint8_t *)&(ps_packet_info->s_llcbuf), 
-                                (uint32_t)ps_packet_info->llcbuf_len);
+                                (uint8_t *)&(s_packet_info.s_llcbuf),
+                                (uint32_t)s_packet_info.llcbuf_len);
 
             if ((NFCSTATUS_PENDING == result) || 
                 (NFCSTATUS_BUSY == PHNFCSTATUS (result)))
diff --git a/src/phLlcNfc_DataTypes.h b/src/phLlcNfc_DataTypes.h
index 2257513..9d5b588 100644
--- a/src/phLlcNfc_DataTypes.h
+++ b/src/phLlcNfc_DataTypes.h
@@ -105,79 +105,81 @@
 #endif /* #if (!defined (LLC_TRACE) && !defined (LLC_DATA_BYTES)) */
 
 
-/* If the below MACRO (RECV_NR_CHECK_ENABLE) is 
-ENABLED : then check for the NR frame received from PN544 in the I frame is 
-    added. This shall be greater than sent NS from the HOST. 
-    This is used to stop the timer 
-DISABLED : dont check the N9R) frame received from the PN544
+/* If the below MACRO (RECV_NR_CHECK_ENABLE) is
+DEFINED : then check for the NR frame received from PN544 in the I frame is
+    added. This shall be greater than sent NS from the HOST.
+    This is used to stop the timer
+COMMENTED : dont check the N(R) frame received from the PN544
 */    
 /* #define RECV_NR_CHECK_ENABLE */
 
-/* If the below MACRO (LLC_UPP_LAYER_NTFY_WRITE_RSP_CB) is 
-ENABLED : then if an I frame is received and the 
-        upper layer response callback (before another READ is pended) is called 
-        only after sending S frame and wait for the callback and then notify the 
+/* If the below MACRO (LLC_UPP_LAYER_NTFY_WRITE_RSP_CB) is
+DEFINED : then if an I frame is received and the
+        upper layer response callback (before another READ is pended) is called
+        only after sending S frame and wait for the callback and then notify the
         upper layer 
-DISABLED : then if an I frame is received and the 
-            upper layer response callback (before another READ is pended) is called 
-            immediately after sending S frame (not waiting for the sent S frame 
+COMMENTED : then if an I frame is received and the
+            upper layer response callback (before another READ is pended) is called
+            immediately after sending S frame (not waiting for the sent S frame
             callback)  
 */
-#define LLC_UPP_LAYER_NTFY_WRITE_RSP_CB
+/* #define LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */
 
-/* PN544 continuously sends an incorrect I frames to the HOST, 
+/* PN544 continuously sends an incorrect I frames to the HOST,
     even after the REJ frame from HOST to PN544
-If the below MACRO (LLC_RR_INSTEAD_OF_REJ) is 
-ENABLED : then if the received NS = (expected NR - 1) then instead of REJ 
+If the below MACRO (LLC_RR_INSTEAD_OF_REJ) is
+DEFINED : then if the received NS = (expected NR - 1) then instead of REJ
         RR frame is sent
-DISABLED : then REJ frame is sent
+COMMENTED : then REJ frame is sent
 */
 #define LLC_RR_INSTEAD_OF_REJ
 
 #define SEND_UFRAME
 
-/* If the below MACRO (CTRL_WIN_SIZE_COUNT) is 
-ENABLED : then window size will be maximum
-DISABLED : then window size is 1
+/* If the below MACRO (CTRL_WIN_SIZE_COUNT) is
+DEFINED : then window size will be maximum
+COMMENTED : then window size is 1
 */
 #define CTRL_WIN_SIZE_COUNT
 
 /* 
 If the below MACRO (LLC_URSET_NO_DELAY) is
-ENABLED : then after receiving the UA frame, then immediately this will be  
+DEFINED : then after receiving the UA frame, then immediately this will be
             notified or further operation will be carried on.
-DISABLED : then after receiving the UA frame, then a timer is started, to  
+COMMENTED : then after receiving the UA frame, then a timer is started, to
             delay the notifiation or to carry on the next operation
 */
 #define LLC_URSET_NO_DELAY 
 
-#ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB
-
-    /* NO definition is required */
-
-#else
-
     /* 
-    This macro is useful only if the LLC_UPP_LAYER_NTFY_WRITE_RSP_CB is DISABLED
     If the below MACRO (LLC_RELEASE_FLAG) is
-    ENABLED : then whenever LLC release is called the g_release_flag variable 
-                will be made TRUE. Also, NO notification is allowed to the 
+DEFINED : then whenever LLC release is called the g_release_flag variable
+                will be made TRUE. Also, NO notification is allowed to the
                 upper layer.
-    DISABLED : g_release_flag is not declared and not used
+COMMENTED : g_release_flag is not declared and not used
     */
     #define LLC_RELEASE_FLAG
 
-#endif /* #ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */
 
  /* 
-    Actually, there is a send and receive error count, if either of them reaches 
+    Actually, there is a send and receive error count, if either of them reaches
     limit, then exception is raised.
     If the below MACRO (LLC_RSET_INSTEAD_OF_EXCEPTION) is
-    ENABLED : then exception is not raised, instead a U RSET command is sent.
-    DISABLED : then exception is raised
+DEFINED : then exception is not raised, instead a U RSET command is sent.
+COMMENTED : then exception is raised
     */
 /* #define LLC_RSET_INSTEAD_OF_EXCEPTION */
 
+#ifndef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB
+    /*
+    If the below MACRO (PIGGY_BACK) is
+    DEFINED : After receiving I frame, wait till the ACK timer to expire to send an ACK to PN544.
+    COMMENTED : immediately ACK the received I frame
+    */
+    #define PIGGY_BACK
+
+#endif /* LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */
+
 #define LLC_SEND_ERROR_COUNT
 
 #define RECV_ERROR_FRAME_COUNT                      (0x50U)
@@ -191,7 +193,7 @@ DISABLED : then after receiving the UA frame, then a timer is started, to
 #define PH_LLCNFC_CRC_LENGTH                        (2)
 #define PH_LLCNFC_MAX_LLC_PAYLOAD                   ((PH_LLCNFC_MAX_IFRAME_BUFLEN) + (4))
 /** Maximum timer used in the Llc */
-#define PH_LLCNFC_MAX_TIMER_USED                    (2)
+#define PH_LLCNFC_MAX_TIMER_USED                    (3)
 /** Maximum timer used in the Llc */
 #define PH_LLCNFC_MAX_ACK_GUARD_TIMER               (4)
 /** Maximum I frame that can be stored */
@@ -496,7 +498,7 @@ typedef struct phLlcNfc_Timerinfo
 
 #ifdef PIGGY_BACK
     /** This will store the ack time out values */
-    uint16_t                ack_to_value[PH_LLCNFC_MAX_ACK_GUARD_TIMER];
+    uint16_t                ack_to_value;
 #endif /* #ifdef PIGGY_BACK */
 
     /** This is a timer flag 
@@ -547,6 +549,9 @@ typedef struct phLlcNfc_Frame
     /** Store the I frames, that has been received, Storage will be 
         till the window size */
     phLlcNfc_StoreIFrame_t          s_recv_store;
+
+    /** Response received count to send the ACK once it reaches the window size */
+    uint8_t                         resp_recvd_count;
 #endif /* #ifdef PIGGY_BACK */
 
     /** To receive the packet sent by below layer */
diff --git a/src/phLlcNfc_Frame.c b/src/phLlcNfc_Frame.c
index 946f67f..af61761 100644
--- a/src/phLlcNfc_Frame.c
+++ b/src/phLlcNfc_Frame.c
@@ -52,7 +52,6 @@
 #ifdef LLC_RELEASE_FLAG
     extern uint8_t             g_release_flag;
 #endif /* #ifdef LLC_RELEASE_FLAG */
-
 /************************ End of global variables *****************************/
 
 /*********************** Local functions ****************************/
@@ -107,28 +106,6 @@ phLlcNfc_H_ProcessSFrame (
 /**
 * \ingroup grp_hal_nfc_llc_helper
 *
-* \brief LLC component <b>Create S frame</b> function
-*
-* \copydoc page_reg This is a helper function which, creates the S frame
-*
-* \param[in/out] psFrameInfo    Generic frame information
-* \param[in/out] cmdType        Command type of S frame
-*
-* \retval NFCSTATUS_SUCCESS                Operation successful.
-* \retval NFCSTATUS_INVALID_PARAMETER      At least one parameter of the function is invalid.
-*
-*/
-static 
-NFCSTATUS
-phLlcNfc_H_CreateSFramePayload (
-    phLlcNfc_Frame_t    *psFrameInfo, 
-    phLlcNfc_LlcCmd_t   cmdType
-);
-
-
-/**
-* \ingroup grp_hal_nfc_llc_helper
-*
 * \brief LLC helper functions <b>Update I frame list</b> function
 *
 * \copydoc page_reg This function checks the nr value with the stored I frames 
@@ -433,10 +410,10 @@ phLlcNfc_H_CreateUFramePayload (
     return result;
 }
 
-static 
 NFCSTATUS
 phLlcNfc_H_CreateSFramePayload (
     phLlcNfc_Frame_t    *psFrameInfo, 
+    phLlcNfc_LlcPacket_t    *psLlcPacket,
     phLlcNfc_LlcCmd_t   cmdType
 )
 {
@@ -451,7 +428,7 @@ phLlcNfc_H_CreateSFramePayload (
     phLlcNfc_Buffer_t       *ps_llc_buf = NULL;
     uint8_t                 length = 0;
     
-    ps_llc_buf = &(psFrameInfo->s_llcpacket.s_llcbuf);
+    ps_llc_buf = &(psLlcPacket->s_llcbuf);
 
     /* Initial S frame header */
     ps_llc_buf->sllcpayload.llcheader = PH_LLCNFC_S_HEADER_INIT;
@@ -467,11 +444,10 @@ phLlcNfc_H_CreateSFramePayload (
                 (ps_llc_buf->sllcpayload.llcheader | (uint8_t)cmdType);
 
     /* Maximum S frame length */
-    psFrameInfo->s_llcpacket.llcbuf_len = (uint8_t)
-                                            PH_LLCNFC_MAX_S_FRAME_LEN;
+    psLlcPacket->llcbuf_len = (uint8_t)PH_LLCNFC_MAX_S_FRAME_LEN;
     /* S frame length byte value */
     ps_llc_buf->llc_length_byte = (uint8_t)
-                            (psFrameInfo->s_llcpacket.llcbuf_len - 1);
+                            (psLlcPacket->llcbuf_len - 1);
 
     /* 
         psFrameInfo->s_llcpacket.s_llcbuf : 
@@ -493,7 +469,7 @@ phLlcNfc_H_CreateSFramePayload (
         (psFrameInfo->s_llcpacket.llcbuf_len - 3) : 
                 is the array index of the second CRC byte to be calculated
     */
-    length = psFrameInfo->s_llcpacket.llcbuf_len;
+    length = psLlcPacket->llcbuf_len;
     phLlcNfc_H_ComputeCrc(
         (uint8_t *)ps_llc_buf, (length - 2),
         &(ps_llc_buf->sllcpayload.llcpayload[(length - 4)]),
@@ -760,7 +736,7 @@ phLlcNfc_H_SendUserIFrame (
 {
     NFCSTATUS               result = NFCSTATUS_SUCCESS;    
     phLlcNfc_Frame_t        *ps_frame_info = NULL;
-    phLlcNfc_LlcPacket_t    *ps_create_packet = NULL;
+    phLlcNfc_LlcPacket_t    s_create_packet;
     phLlcNfc_LlcPacket_t    *ps_get_packet = NULL;
     phLlcNfc_Payload_t      *ps_llc_payload = NULL;
     phLlcNfc_StoreIFrame_t  *ps_store_frame = NULL;
@@ -778,7 +754,6 @@ phLlcNfc_H_SendUserIFrame (
     else
     {
         ps_frame_info = &(psLlcCtxt->s_frameinfo);
-        ps_create_packet = &(ps_frame_info->s_llcpacket);
         ps_store_frame = &(ps_frame_info->s_send_store);
 
         if (
@@ -788,7 +763,7 @@ phLlcNfc_H_SendUserIFrame (
         {
             /* Get the stored I frame, only if the new frame is sent 
                 from the upper layer */
-            result = phLlcNfc_H_IFrameList_Peek (psListInfo, &ps_get_packet, 
+            result = phLlcNfc_H_IFrameList_Peek (psListInfo, &ps_get_packet,
                                                 ps_frame_info->n_s);
         }
 
@@ -800,25 +775,25 @@ phLlcNfc_H_SendUserIFrame (
             llc_header = (uint8_t)(llc_header | ps_frame_info->n_r);
 
             /* Create the packet */
-            (void)memcpy ((void *)ps_create_packet, (void *)ps_get_packet, 
+            (void)memcpy ((void *)&(s_create_packet), (void *)ps_get_packet,
                         sizeof (phLlcNfc_LlcPacket_t));
 
-            ps_create_packet->s_llcbuf.sllcpayload.llcheader = llc_header;
-            ps_llc_payload = &(ps_create_packet->s_llcbuf.sllcpayload);
+            s_create_packet.s_llcbuf.sllcpayload.llcheader = llc_header;
+            ps_llc_payload = &(s_create_packet.s_llcbuf.sllcpayload);
 
             /* Length of the complete llc buffer, sent to PN544 */
-            length = ps_create_packet->llcbuf_len;
+            length = s_create_packet.llcbuf_len;
 
             /* Compute CRC for the created packet */
-            phLlcNfc_H_ComputeCrc ((uint8_t *)&(ps_create_packet->s_llcbuf), 
+            phLlcNfc_H_ComputeCrc ((uint8_t *)&(s_create_packet.s_llcbuf),
                         (length - 2),
                         (uint8_t *)&(ps_llc_payload->llcpayload[(length - 4)]), 
                         (uint8_t *)&(ps_llc_payload->llcpayload[(length - 3)]));
 
             /* Send the i frame */
-            result = phLlcNfc_Interface_Write (psLlcCtxt, 
-                            (uint8_t *)&(ps_create_packet->s_llcbuf), 
-                            (uint32_t)ps_create_packet->llcbuf_len);
+            result = phLlcNfc_Interface_Write (psLlcCtxt,
+                            (uint8_t *)&(s_create_packet.s_llcbuf),
+                            (uint32_t)s_create_packet.llcbuf_len);
 
             ps_frame_info->write_status = result;
 
@@ -865,7 +840,7 @@ phLlcNfc_H_SendRejectedIFrame (
 {
     NFCSTATUS               result = NFCSTATUS_SUCCESS;    
     phLlcNfc_Frame_t        *ps_frame_info = NULL;
-    phLlcNfc_LlcPacket_t    *ps_create_packet = NULL;
+    phLlcNfc_LlcPacket_t    s_create_packet;
     phLlcNfc_LlcPacket_t    *ps_get_packet = NULL;
     phLlcNfc_Payload_t      *ps_llc_payload = NULL;
     phLlcNfc_StoreIFrame_t  *ps_store_frame = NULL;
@@ -883,7 +858,6 @@ phLlcNfc_H_SendRejectedIFrame (
     else
     {
         ps_frame_info = &(psLlcCtxt->s_frameinfo);
-        ps_create_packet = &(ps_frame_info->s_llcpacket);
         ps_store_frame = &(ps_frame_info->s_send_store);
 
 
@@ -898,7 +872,7 @@ phLlcNfc_H_SendRejectedIFrame (
                 ps_store_frame->s_llcpacket[ns_rejected].frame_to_send)
             {
                 /* Above check is added to know only if   */
-                result = phLlcNfc_H_IFrameList_Peek (psListInfo, &ps_get_packet, 
+                result = phLlcNfc_H_IFrameList_Peek (psListInfo, &ps_get_packet,
                                                     ns_rejected);
             }
             else
@@ -918,25 +892,25 @@ phLlcNfc_H_SendRejectedIFrame (
             llc_header = (uint8_t)(llc_header | ps_frame_info->n_r);
 
             /* Create the packet */
-            (void)memcpy ((void *)ps_create_packet, (void *)ps_get_packet, 
+            (void)memcpy ((void *)&(s_create_packet), (void *)ps_get_packet,
                         sizeof (phLlcNfc_LlcPacket_t));
 
-            ps_create_packet->s_llcbuf.sllcpayload.llcheader = llc_header;
-            ps_llc_payload = &(ps_create_packet->s_llcbuf.sllcpayload);
+            s_create_packet.s_llcbuf.sllcpayload.llcheader = llc_header;
+            ps_llc_payload = &(s_create_packet.s_llcbuf.sllcpayload);
 
             /* Length of the complete llc buffer, sent to PN544 */
-            length = ps_create_packet->llcbuf_len;
+            length = s_create_packet.llcbuf_len;
 
             /* Compute CRC for the created packet */
-            phLlcNfc_H_ComputeCrc ((uint8_t *)&(ps_create_packet->s_llcbuf), 
+            phLlcNfc_H_ComputeCrc ((uint8_t *)&(s_create_packet.s_llcbuf),
                         (length - 2),
                         (uint8_t *)&(ps_llc_payload->llcpayload[(length - 4)]), 
                         (uint8_t *)&(ps_llc_payload->llcpayload[(length - 3)]));
 
             /* Send the i frame */
             result = phLlcNfc_Interface_Write (psLlcCtxt, 
-                            (uint8_t *)&(ps_create_packet->s_llcbuf), 
-                            (uint32_t)ps_create_packet->llcbuf_len);
+                            (uint8_t *)&(s_create_packet.s_llcbuf),
+                            (uint32_t)s_create_packet.llcbuf_len);
 
             ps_frame_info->write_status = result;
 
@@ -946,7 +920,7 @@ phLlcNfc_H_SendRejectedIFrame (
                     so update the below variable */
                 ps_frame_info->write_wait_call = (phLlcNfc_eSentFrameType_t)
                                 (((ns_rejected != ps_store_frame->start_pos) && 
-                                (resend_i_frame != ps_frame_info->write_wait_call))? 
+                                (resend_i_frame != ps_frame_info->write_wait_call))?
                                 rejected_i_frame : ps_frame_info->write_wait_call);
             }
             else
@@ -1009,7 +983,7 @@ phLlcNfc_H_SendTimedOutIFrame (
     NFCSTATUS               result = NFCSTATUS_SUCCESS;    
     phLlcNfc_Frame_t        *ps_frame_info = NULL;
     phLlcNfc_Timerinfo_t    *ps_timer_info = NULL;
-    phLlcNfc_LlcPacket_t    *ps_create_packet = NULL;
+    phLlcNfc_LlcPacket_t    s_create_packet;
     phLlcNfc_LlcPacket_t    *ps_get_packet = NULL;
     phLlcNfc_Payload_t      *ps_llc_payload = NULL;
     phLlcNfc_StoreIFrame_t  *ps_store_frame = NULL;
@@ -1033,7 +1007,6 @@ phLlcNfc_H_SendTimedOutIFrame (
 
         ps_frame_info = &(psLlcCtxt->s_frameinfo);
         ps_timer_info = &(psLlcCtxt->s_timerinfo);
-        ps_create_packet = &(ps_frame_info->s_llcpacket);
         ps_store_frame = &(ps_frame_info->s_send_store);        
         
         timer_index = ps_timer_info->index_to_send;
@@ -1043,12 +1016,13 @@ phLlcNfc_H_SendTimedOutIFrame (
         PH_LLCNFC_DEBUG("SEND TIMEOUT CALL WIN SIZE CNT : 0x%02X\n", ps_store_frame->winsize_cnt);
         PH_LLCNFC_DEBUG("SEND TIMEOUT CALL START POS : 0x%02X\n", ps_store_frame->start_pos);
         PH_LLCNFC_DEBUG("SEND TIMEOUT CALL N S value : 0x%02X\n", ps_frame_info->n_s);
+        PH_LLCNFC_DEBUG("SEND TIMEOUT TIMER INDEX : 0x%02X\n", timer_index);
         PH_LLCNFC_DEBUG("SEND TIMEOUT CALL frame type : 0x%02X\n", ps_timer_info->frame_type[timer_index]);
 
         if (resend_i_frame == ps_timer_info->frame_type[timer_index])
         {
             /* Get the stored I frame */
-            result = phLlcNfc_H_IFrameList_Peek (psListInfo, &ps_get_packet, 
+            result = phLlcNfc_H_IFrameList_Peek (psListInfo, &ps_get_packet,
                                                 ns_index);
         }        
 
@@ -1061,25 +1035,25 @@ phLlcNfc_H_SendTimedOutIFrame (
             llc_header = (uint8_t)(llc_header | ps_frame_info->n_r);
 
             /* create the packet */
-            (void)memcpy ((void *)ps_create_packet, (void *)ps_get_packet, 
+            (void)memcpy ((void *)&(s_create_packet), (void *)ps_get_packet,
                         sizeof (phLlcNfc_LlcPacket_t));
 
-            ps_create_packet->s_llcbuf.sllcpayload.llcheader = llc_header;
-            ps_llc_payload = &(ps_create_packet->s_llcbuf.sllcpayload);
+            s_create_packet.s_llcbuf.sllcpayload.llcheader = llc_header;
+            ps_llc_payload = &(s_create_packet.s_llcbuf.sllcpayload);
 
             /* Length of the complete llc buffer, sent to PN544 */
-            length = ps_create_packet->llcbuf_len;
+            length = s_create_packet.llcbuf_len;
 
             /* Compute CRC */
-            phLlcNfc_H_ComputeCrc((uint8_t *)&(ps_create_packet->s_llcbuf), 
+            phLlcNfc_H_ComputeCrc((uint8_t *)&(s_create_packet.s_llcbuf),
                         (length - 2),
-                        (uint8_t *)&(ps_llc_payload->llcpayload[(length - 4)]), 
+                        (uint8_t *)&(ps_llc_payload->llcpayload[(length - 4)]),
                         (uint8_t *)&(ps_llc_payload->llcpayload[(length - 3)]));
 
             /* Send the i frame */
             result = phLlcNfc_Interface_Write (psLlcCtxt, 
-                            (uint8_t *)&(ps_create_packet->s_llcbuf), 
-                            (uint32_t)ps_create_packet->llcbuf_len);
+                            (uint8_t *)&(s_create_packet.s_llcbuf),
+                            (uint32_t)s_create_packet.llcbuf_len);
 
             ps_frame_info->write_status = result;
             PH_LLCNFC_DEBUG("SEND TIMEOUT CALL Write status : 0x%02X\n", result);
@@ -1102,9 +1076,9 @@ phLlcNfc_H_SendTimedOutIFrame (
 
                 PH_LLCNFC_DEBUG("SEND TIMEOUT CALL timer index : 0x%02X\n", timer_index);
 
-                PH_LLCNFC_DEBUG("SEND TIMEOUT CALL GUARD TO VALUE : 0x%02X\n", ps_timer_info->guard_to_value[(timer_index - 1)]);
                 if (timer_index > 0)
                 {                    
+                    PH_LLCNFC_DEBUG("SEND TIMEOUT CALL GUARD TO VALUE : 0x%02X\n", ps_timer_info->guard_to_value[(timer_index - 1)]);
                     /* Copy the maximum time-out value. */
                     time_out_value = (uint16_t)
                         ((ps_timer_info->guard_to_value[(timer_index - 1)] >= 
@@ -1212,12 +1186,6 @@ phLlcNfc_H_ProcessIFrame (
     uint8_t                     recvd_nr = 0;    
 #endif /* #ifdef RECV_NR_CHECK_ENABLE */
 
-#ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB
-    /* Nothing required in this define */
-#else
-    uint8_t                     prev_local_nr = 0;
-#endif /* #ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */
-
     ps_frame_info = &(psLlcCtxt->s_frameinfo);
     ps_store_frame = &(ps_frame_info->s_send_store);
     ps_recv_pkt = &(ps_frame_info->s_recvpacket);
@@ -1259,12 +1227,6 @@ phLlcNfc_H_ProcessIFrame (
         phLlcNfc_StopTimers (PH_LLCNFC_GUARDTIMER, no_of_del_frames);
     }
 
-#ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB
-    /* Nothing required in this define */
-#else
-    prev_local_nr = ps_frame_info->n_r;
-#endif /* #ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */
-
     /* Received buffer, N(S) value = N(R) of host (our 
         structure) then send RR type of s frame else send 
         REJ type of s frame */
@@ -1290,7 +1252,6 @@ phLlcNfc_H_ProcessIFrame (
                         ps_recv_pkt->s_llcbuf.sllcpayload.llcpayload), 
                         psLlcCtxt->recvbuf_length);
         
-        
 #if defined (LLC_SEND_RR_ACK)
 
         if (((ns_index < ps_frame_info->n_r) && 
@@ -1309,6 +1270,11 @@ phLlcNfc_H_ProcessIFrame (
             ps_frame_info->n_r = ((ps_frame_info->n_r + 1)
                                     % PH_LLCNFC_MOD_NS_NR);
 
+#ifdef PIGGY_BACK
+            ps_frame_info->resp_recvd_count = (uint8_t)
+                                    (ps_frame_info->resp_recvd_count + 1);
+#endif /* #ifdef PIGGY_BACK */
+
         }
 
         if (NFCSTATUS_BUSY == PHNFCSTATUS (ps_frame_info->write_status))
@@ -1334,9 +1300,7 @@ phLlcNfc_H_ProcessIFrame (
         {
             dont_send_s_frame = TRUE;
 #ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB
-
             phLlcNfc_H_SendInfo (psLlcCtxt);
-
 #endif /* #ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */        
         }
         else
@@ -1349,15 +1313,10 @@ phLlcNfc_H_ProcessIFrame (
                             resend_s_frame : s_frame);
         }
 
-#ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB
-
-        /* Nothing required in this define */
-
-#else /* #ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */
-
+#ifdef PIGGY_BACK
         phLlcNfc_H_SendInfo (psLlcCtxt);
+#endif /* #ifdef PIGGY_BACK */
 
-#endif /* #ifdef LLC_UPP_LAYER_NTFY_WRITE_RSP_CB */
     }
     else
     {
@@ -1425,23 +1384,61 @@ phLlcNfc_H_ProcessIFrame (
 
 #endif /* #ifdef LLC_RELEASE_FLAG */
     {
-        result = phLlcNfc_Interface_Read(psLlcCtxt, 
+        (void)phLlcNfc_Interface_Read(psLlcCtxt,
                         PH_LLCNFC_READWAIT_OFF, 
                         &(ps_recv_pkt->s_llcbuf.llc_length_byte),
                         (uint8_t)PH_LLCNFC_BYTES_INIT_READ);
     
+#ifdef PIGGY_BACK
+        /* Check if any write call is performed or not */
+        if (NFCSTATUS_PENDING != result)
+        {
+            /* No write is performed, So, now check */
+            if (NFCSTATUS_BUSY == PHNFCSTATUS (ps_frame_info->write_status))
+            {
+                /* Any how write cannot be done and some frame is ready to be sent
+                so this frame will act as the ACK */
+                result = phLlcNfc_H_WriteWaitCall (psLlcCtxt);
+            }
+        }
+
+        if (NFCSTATUS_PENDING != result)
+        {
+            if (ps_frame_info->window_size == ps_frame_info->resp_recvd_count)
+            {
+                phLlcNfc_LlcPacket_t    s_packet_info;
+                /* Create S frame */
+                (void)phLlcNfc_H_CreateSFramePayload (ps_frame_info, &(s_packet_info), cmdtype);
 
+                result = phLlcNfc_Interface_Write(psLlcCtxt,
+                            (uint8_t *)&(s_packet_info.s_llcbuf),
+                            (uint32_t)(s_packet_info.llcbuf_len));
+
+
+                if (0 == ps_frame_info->send_error_count)
+                {
+                    ps_frame_info->write_wait_call = invalid_frame;
+                }
+                ps_frame_info->sent_frame_type = eframe_type;
+            }
+            else
+            {
+                result = phLlcNfc_StartTimers (PH_LLCNFC_ACKTIMER, 0);
+            }
+        }
+#else /* #ifdef PIGGY_BACK */
 
         if ((TRUE != ps_frame_info->write_pending) &&  
             (PH_LLCNFC_READPEND_REMAIN_BYTE != ps_frame_info->read_pending) && 
             (FALSE == dont_send_s_frame))
         {
+            phLlcNfc_LlcPacket_t    s_packet_info = {0};
             /* Create S frame */
-            (void)phLlcNfc_H_CreateSFramePayload (ps_frame_info, cmdtype);
+            (void)phLlcNfc_H_CreateSFramePayload (ps_frame_info, &(s_packet_info), cmdtype);
 
             result = phLlcNfc_Interface_Write(psLlcCtxt,
-                        (uint8_t *)&(ps_frame_info->s_llcpacket.s_llcbuf), 
-                        (uint32_t)(ps_frame_info->s_llcpacket.llcbuf_len));
+                        (uint8_t *)&(s_packet_info.s_llcbuf),
+                        (uint32_t)(s_packet_info.llcbuf_len));
 
 
             if (0 == ps_frame_info->send_error_count)
@@ -1450,6 +1447,7 @@ phLlcNfc_H_ProcessIFrame (
             }
             ps_frame_info->sent_frame_type = eframe_type;
         }
+#endif /* #ifdef PIGGY_BACK */
     }
 
     return ;
@@ -1962,13 +1960,16 @@ phLlcNfc_H_SendRejectFrame(
                       )
 {
     NFCSTATUS       result = NFCSTATUS_SUCCESS;
+    phLlcNfc_LlcPacket_t    s_packet_info = {0};
+
     result = phLlcNfc_H_CreateSFramePayload(
-                                    &(psLlcCtxt->s_frameinfo), 
+                                    &(psLlcCtxt->s_frameinfo),
+                                    &(s_packet_info),
                                     phLlcNfc_e_rej);
     /* Send the "S" frame to the lower layer */
     result = phLlcNfc_Interface_Write(psLlcCtxt,
-        (uint8_t *)&(psLlcCtxt->s_frameinfo.s_llcpacket.s_llcbuf), 
-        (uint32_t)(psLlcCtxt->s_frameinfo.s_llcpacket.llcbuf_len));
+        (uint8_t *)&(s_packet_info.s_llcbuf),
+        (uint32_t)(s_packet_info.llcbuf_len));
 
     if (NFCSTATUS_PENDING == result)
     {
@@ -2160,23 +2161,22 @@ phLlcNfc_H_SendRSETFrame (
                       )
 {
     NFCSTATUS                   result = NFCSTATUS_SUCCESS;
-    phLlcNfc_LlcPacket_t        *ps_packet_info = NULL;
+    phLlcNfc_LlcPacket_t        s_packet_info;
     phLlcNfc_Frame_t            *ps_frame_info = NULL;
     
     ps_frame_info = &(psLlcCtxt->s_frameinfo);
-    ps_packet_info = &(psLlcCtxt->s_frameinfo.s_llcpacket);
 
-    result = phLlcNfc_H_CreateUFramePayload(psLlcCtxt, 
-                                    ps_packet_info, 
-                                    &(ps_packet_info->llcbuf_len), 
+    result = phLlcNfc_H_CreateUFramePayload(psLlcCtxt,
+                                    &(s_packet_info),
+                                    &(s_packet_info.llcbuf_len),
                                     phLlcNfc_e_rset);
 
     if (NFCSTATUS_SUCCESS == result)
     {
         /* Call DAL write */
-        result = phLlcNfc_Interface_Write(psLlcCtxt, 
-                            (uint8_t*)&(ps_packet_info->s_llcbuf), 
-                            (uint32_t)ps_packet_info->llcbuf_len);
+        result = phLlcNfc_Interface_Write(psLlcCtxt,
+                            (uint8_t*)&(s_packet_info.s_llcbuf),
+                            (uint32_t)s_packet_info.llcbuf_len);
     }
 
     ps_frame_info->write_status = result;
diff --git a/src/phLlcNfc_Frame.h b/src/phLlcNfc_Frame.h
index e1662df..e76e017 100644
--- a/src/phLlcNfc_Frame.h
+++ b/src/phLlcNfc_Frame.h
@@ -264,6 +264,7 @@ phLlcNfc_H_CreateUFramePayload (
 *
 * \param[in/out]    psFrameInfo Information related to LLC frames are stored 
 *                           in this structure
+* \param[in/out]    psLlcPacket         Llc packet sent by the upper layer
 * \param[in]        pLlcBuf     User given buffer or the buffer which needs LLC framing
 * \param[in]        llcBufLength    Length of the parameter "pLlcBuf" 
 *
@@ -427,6 +428,28 @@ phLlcNfc_H_SendRejectedIFrame (
 /**
 * \ingroup grp_hal_nfc_llc_helper
 *
+* \brief LLC component <b>Create S frame</b> function
+*
+* \copydoc page_reg This is a helper function which, creates the S frame
+*
+* \param[in/out] psFrameInfo    Generic frame information
+* \param[in/out] psLlcPacket         Llc packet sent by the upper layer
+* \param[in/out] cmdType        Command type of S frame
+*
+* \retval NFCSTATUS_SUCCESS                Operation successful.
+* \retval NFCSTATUS_INVALID_PARAMETER      At least one parameter of the function is invalid.
+*
+*/
+NFCSTATUS
+phLlcNfc_H_CreateSFramePayload (
+    phLlcNfc_Frame_t        *psFrameInfo,
+    phLlcNfc_LlcPacket_t    *psLlcPacket,
+    phLlcNfc_LlcCmd_t       cmdType
+);
+
+/**
+* \ingroup grp_hal_nfc_llc_helper
+*
 * \brief LLC Send upper layer information function
 *
 * \copydoc page_reg Sends received information to the upper layer frame.
diff --git a/src/phLlcNfc_Interface.c b/src/phLlcNfc_Interface.c
index 871481b..a1e9938 100644
--- a/src/phLlcNfc_Interface.c
+++ b/src/phLlcNfc_Interface.c
@@ -48,7 +48,6 @@
 /***************************** Macros *******************************/
 #define PH_LLCNFC_APPEND_LEN                        (4)
 #define LLC_NS_FRAME_HEADER_MASK                    (0x38U)
-
 /************************ End of macros *****************************/
 
 /*********************** Local functions ****************************/
@@ -81,8 +80,8 @@ phLlcNfc_Interface_Register(
 )
 {
     NFCSTATUS                   result = NFCSTATUS_SUCCESS;
-    phNfcIF_sCallBack_t         if_cb;
-    phNfcIF_sReference_t        sreference;
+    phNfcIF_sCallBack_t         if_cb = {0,0,0,0};
+    phNfcIF_sReference_t        sreference = {0,0,0};
     
     if ((NULL == psLlcCtxt) || (NULL == psIFConfig))
     {
@@ -247,13 +246,24 @@ phLlcNfc_Interface_Write(
             PH_LLCNFC_STRING (";\n");
     
 #endif /* LLC_DATA_BYTES */
+
+            psLlcCtxt->s_frameinfo.s_llcpacket.llcbuf_len = (uint8_t)llcBufferLength;
+            (void)memcpy ((void *)&(psLlcCtxt->s_frameinfo.s_llcpacket.s_llcbuf),
+                        (void *)pLlcBuffer, llcBufferLength);
+
             result = psLlcCtxt->lower_if.send(psLlcCtxt->lower_if.pcontext, 
                                                 psLlcCtxt->phwinfo, 
-                                                pLlcBuffer, 
+                                                (uint8_t *)&(psLlcCtxt->s_frameinfo.s_llcpacket.s_llcbuf),
                                                 (uint16_t)llcBufferLength);
             if(NFCSTATUS_PENDING == result)
             {
                 psLlcCtxt->s_frameinfo.write_pending = TRUE;
+#ifdef PIGGY_BACK
+                /* Stop the ACK timer, as the ACK or I frame is sent */
+                phLlcNfc_StopTimers (PH_LLCNFC_ACKTIMER, 0);
+                /* ACK is sent, so reset the response received count */
+                psLlcCtxt->s_frameinfo.resp_recvd_count = 0;
+#endif /* #ifdef PIGGY_BACK */
             }
         }
     }
@@ -279,7 +289,7 @@ phLlcNfc_WrResp_Cb(
     phLlcNfc_Frame_t            *ps_frame_info = NULL;
     phLlcNfc_LlcPacket_t        *ps_recv_pkt = NULL;
     phLlcNfc_StoreIFrame_t      *ps_store_frame = NULL;
-    phNfc_sCompletionInfo_t     notifyinfo;
+    phNfc_sCompletionInfo_t     notifyinfo = {0,0,0};
     uint8_t                     count = 0;
 
     PH_LLCNFC_PRINT("\n\nLLC : WRITE RESP CB CALLED\n\n");
@@ -497,6 +507,7 @@ phLlcNfc_WrResp_Cb(
                     }
                     else 
                     {
+                        /* ***** This notification needs to be disabled ***** */
                         if(NULL != ps_llc_ctxt->cb_for_if.send_complete) 
                         {
                             pCompInfo->length = (pCompInfo->length - 
@@ -650,7 +661,7 @@ phLlcNfc_RdResp_Cb(
     phLlcNfc_LlcPacket_t        *ps_recv_pkt = NULL;
     phLlcNfc_Payload_t          *ps_llc_payload = NULL;
     pphNfcIF_Notification_CB_t  notifyul = NULL;
-    phNfc_sCompletionInfo_t     notifyinfo;
+    phNfc_sCompletionInfo_t     notifyinfo = {0,0,0};
 
     PH_LLCNFC_PRINT("\n\nLLC : READ RESP CB CALLED\n\n");
     
@@ -932,7 +943,7 @@ phLlcNfc_H_SendInfo (
 {
     phLlcNfc_LlcPacket_t        *ps_recv_pkt = NULL;
     phLlcNfc_Frame_t            *ps_frame_info = NULL;
-    phNfc_sTransactionInfo_t    comp_info;
+    phNfc_sTransactionInfo_t    comp_info = {0,0,0,0,0};
 
     ps_frame_info = &(psLlcCtxt->s_frameinfo);
     ps_recv_pkt = &(ps_frame_info->s_recvpacket);
diff --git a/src/phLlcNfc_Timer.c b/src/phLlcNfc_Timer.c
index c079760..06ca7e4 100644
--- a/src/phLlcNfc_Timer.c
+++ b/src/phLlcNfc_Timer.c
@@ -44,8 +44,6 @@
 /***************************** Macros *******************************/
 /**< Timer for connection timer index */
 #define PH_LLCNFC_CONNECTION_TO_INDEX       (0x00)
-/**< 0x0A Timer for ack time out value */
-#define PH_LLCNFC_ACK_TO_VALUE              (1000)
 /**< Maximum guard timer can be present */
 #define PH_LLCNFC_MAX_GUARD_TIMER           (0x04)
 /** Connection time out bit to set */
@@ -60,6 +58,8 @@
 #define PH_LLCNFC_CON_TO_BIT_VAL            (0x01)
 /** Guard time out bit to set */
 #define PH_LLCNFC_GUARD_TO_BIT_VAL          (0x02)
+/** ACK time out bit to set */
+#define PH_LLCNFC_ACK_TO_BIT_VAL            (0x04)
 
 #define GUARD_TO_URSET
 
@@ -84,7 +84,7 @@ void
 phLlcNfc_AckTimeoutCb (
     uint32_t TimerId                    
 );
-#endif
+#endif /* #ifdef PIGGY_BACK */
 
 /* This callback is for connection time out */
 static 
@@ -290,17 +290,22 @@ phLlcNfc_StartTimers (
             /* Get the ack timer flag */
             timerstarted = (uint8_t)GET_BITS8 (
                                     ps_timer_info->timer_flag, 
-                                    PH_LLCNFC_GUARD_TO_BIT, 
+                                    PH_LLCNFC_ACK_TO_BIT,
                                     PH_LLCNFC_TO_NOOFBITS);
-            if (0 == timerstarted)
+
+            if (FALSE == timerstarted)
             {
                 /* Timer not started, so start the timer */
                 ps_timer_info->timer_flag = (uint8_t)
                                 SET_BITS8 (ps_timer_info->timer_flag, 
-                                        PH_LLCNFC_GUARD_TO_BIT
-                                        PH_LLCNFC_TO_NOOFBITS
-                                        (PH_LLCNFC_GUARD_TO_BIT - 1));
+                                        PH_LLCNFC_ACK_TO_BIT,
+                                        PH_LLCNFC_TO_NOOFBITS,
+                                        (PH_LLCNFC_ACK_TO_BIT - 1));
             }
+
+
+            timer_resolution = ps_timer_info->ack_to_value = (uint16_t)
+                                            PH_LLCNFC_ACK_TO_VALUE;
             timerid = ps_timer_info->timer_id[PH_LLCNFC_ACKTIMER];
             Callback = (ppCallBck_t)&phLlcNfc_AckTimeoutCb;
             break;
@@ -380,7 +385,7 @@ phLlcNfc_StopTimers (
             {
                 /* The number of guard timer count is more than the 
                     guard timer to delete  */
-                while (start_index < no_of_guard_to_del)
+                while (start_index < (timer_count - no_of_guard_to_del))
                 {
                     /* Copy the previous stored timer values to the present */
                     ps_timer_info->guard_to_value[start_index] = (uint16_t)
@@ -457,11 +462,14 @@ phLlcNfc_StopTimers (
 #ifdef PIGGY_BACK
         case PH_LLCNFC_ACKTIMER:
         {
+            timerflag = (timerflag & PH_LLCNFC_ACK_TO_BIT_VAL);
+
             ps_timer_info->timer_flag = (uint8_t)
                                 SET_BITS8 (ps_timer_info->timer_flag, 
-                                        PH_LLCNFC_GUARD_TO_BIT, 
+                                        PH_LLCNFC_ACK_TO_BIT,
                                         PH_LLCNFC_TO_NOOFBITS, 0);
             timerid = ps_timer_info->timer_id[PH_LLCNFC_ACKTIMER];
+            ps_timer_info->ack_to_value = 0;
             break;
         }
 #endif /* #ifdef PIGGY_BACK */
@@ -486,7 +494,7 @@ phLlcNfc_StopTimers (
 
     PHNFC_UNUSED_VARIABLE (result);
     PHNFC_UNUSED_VARIABLE (TimerType);
-    PHNFC_UNUSED_VARIABLE (no_of_gaurd_to_del);
+    PHNFC_UNUSED_VARIABLE (no_of_guard_to_del);
 
 #endif /* #ifdef LLC_TIMER_ENABLE */
 }
@@ -602,23 +610,25 @@ phLlcNfc_GuardTimeoutCb (
     NFCSTATUS                   result = NFCSTATUS_SUCCESS;
     phLlcNfc_Timerinfo_t        *ps_timer_info = NULL;
     phLlcNfc_Frame_t            *ps_frame_info = NULL;
-    phLlcNfc_LlcPacket_t        *ps_packet_info = NULL;
+    phLlcNfc_LlcPacket_t        s_packet_info;
     uint8_t                     index = 0;
+    /* zero_to_index = Time out index has become 0 */
     uint8_t                     zero_to_index = 0;
+
 #if defined (GUARD_TO_ERROR)
     phNfc_sCompletionInfo_t     notifyinfo = {0,0,0};
 #endif /* #if defined (GUARD_TO_ERROR) */
-    PHNFC_UNUSED_VARIABLE(pContext);
 
     PH_LLCNFC_PRINT("\n\nLLC : GUARD TIMEOUT CB CALLED \n\n");
 
-    if ((NULL != gpphLlcNfc_Ctxt) && (TimerId == 
-        gpphLlcNfc_Ctxt->s_timerinfo.timer_id[PH_LLCNFC_GUARDTIMER]) && 
-        (PH_LLCNFC_GUARD_TO_BIT_VAL == 
-        (gpphLlcNfc_Ctxt->s_timerinfo.timer_flag & 
+    if ((NULL != gpphLlcNfc_Ctxt) && (TimerId ==
+        gpphLlcNfc_Ctxt->s_timerinfo.timer_id[PH_LLCNFC_GUARDTIMER]) &&
+        (PH_LLCNFC_GUARD_TO_BIT_VAL ==
+        (gpphLlcNfc_Ctxt->s_timerinfo.timer_flag &
         PH_LLCNFC_GUARD_TO_BIT_VAL)))
     {
         uint8_t                 timer_expired = FALSE;
+
         ps_frame_info = &(gpphLlcNfc_Ctxt->s_frameinfo);
         ps_timer_info = &(gpphLlcNfc_Ctxt->s_timerinfo);
 
@@ -632,8 +642,15 @@ phLlcNfc_GuardTimeoutCb (
            send called */
         while (index < ps_timer_info->guard_to_count) 
         {
+            /* This loop runs for all the timer present in the data structure.
+                This means if there are 2 I frame has been sent and
+                response is not received for the I frames sent then the
+                each time this timer expires, the time out value is decremented
+                by the PH_LLCNFC_RESOLUTION value */
             if (0 != ps_timer_info->guard_to_value[index])
             {
+                /* If timer value is not zero then enter,
+                    this means that the value is not zero */
                 if (ps_timer_info->guard_to_value[index] > 0)
                 {
                     if (ps_timer_info->guard_to_value[index] >= 
@@ -651,10 +668,20 @@ phLlcNfc_GuardTimeoutCb (
 
                 if (0 == ps_timer_info->guard_to_value[index])
                 {
+                    /* Timer value has expired, so resend has to be done
+                        Timer value is 0 */
+                    ps_timer_info->frame_type[index] = (uint8_t)resend_i_frame;
+                    if (FALSE == timer_expired)
+                    {
+                        /* As the statement is in the loop, so there are possibilities
+                            of more than 1 timer value can be 0, so if previous timer
+                            value has already been 0, then again dont change the
+                            index */
                     zero_to_index = index;
                     timer_expired = TRUE;
                 }
             }
+            }
             index = (uint8_t)(index + 1);
         }
 
@@ -686,7 +713,6 @@ phLlcNfc_GuardTimeoutCb (
 
                     timer_count = ps_timer_info->guard_to_count;
 
-                    
                     /* Check before changing the index to resend, if index 
                         already exist then dont set the index */
                     while ((FALSE == while_exit) && (start_index < timer_count))
@@ -702,13 +728,29 @@ phLlcNfc_GuardTimeoutCb (
                         }
                     }
 
-                    if (TRUE == while_exit)
+                    if (FALSE == while_exit)
                     {
+                        /* This " ps_timer_info->index_to_send " member is
+                           useful, when 2 time out values are 0, then
+                           only first timed out value has to be resent and
+                           other has to wait until the the first timed out
+                           I frame is resent
+                           This statement is executed only if, none of the timer
+                           has expires previously, this is the first timer in the
+                           list that has time out value has 0
+                           */
                         ps_timer_info->index_to_send = zero_to_index;
                     }
+                    else
+                    {
+                        /* This statement is executed only if, any one of the time
+                           out value was 0 previously, so first resend has to be done
+                           for the previous I frame, so the index is set to the previous
+                           I frame
+                           */
+                        ps_timer_info->index_to_send = start_index;
+                    }
 
-                    ps_timer_info->frame_type[zero_to_index] = (uint8_t)
-                                                            resend_i_frame;
                     /* Now resend the frame stored */
                     result = phLlcNfc_H_SendTimedOutIFrame (gpphLlcNfc_Ctxt, 
                                             &(ps_frame_info->s_send_store), 
@@ -741,16 +783,15 @@ phLlcNfc_GuardTimeoutCb (
 #if (!defined (GUARD_TO_ERROR) && defined (GUARD_TO_URSET))
 
                     PH_LLCNFC_PRINT("U-RSET IS SENT \n");
-                    ps_packet_info = &(gpphLlcNfc_Ctxt->s_frameinfo.s_llcpacket);
 
-                    result = phLlcNfc_H_CreateUFramePayload(gpphLlcNfc_Ctxt, 
-                                        ps_packet_info, 
-                                        &(ps_packet_info->llcbuf_len), 
+                    result = phLlcNfc_H_CreateUFramePayload(gpphLlcNfc_Ctxt,
+                                        &(s_packet_info),
+                                        &(s_packet_info.llcbuf_len),
                                         phLlcNfc_e_rset);
 
-                    result = phLlcNfc_Interface_Write(gpphLlcNfc_Ctxt, 
-                                    (uint8_t*)&(ps_packet_info->s_llcbuf), 
-                                    (uint32_t)ps_packet_info->llcbuf_len);
+                    result = phLlcNfc_Interface_Write(gpphLlcNfc_Ctxt,
+                                    (uint8_t*)&(s_packet_info.s_llcbuf),
+                                    (uint32_t)s_packet_info.llcbuf_len);
 
                     ps_frame_info->write_status = result;
                     if (NFCSTATUS_PENDING == result)
@@ -782,15 +823,71 @@ phLlcNfc_GuardTimeoutCb (
 }
 
 #ifdef PIGGY_BACK
+
 static 
 void 
 phLlcNfc_AckTimeoutCb (
     uint32_t TimerId
 )
 {
+    NFCSTATUS                   result = NFCSTATUS_SUCCESS;
+    phLlcNfc_Frame_t            *ps_frame_info = NULL;
+    phLlcNfc_Timerinfo_t        *ps_timer_info = NULL;
+    phLlcNfc_LlcPacket_t        s_packet_info;
+
+    PH_LLCNFC_PRINT("\n\nLLC : ACK TIMEOUT CB CALLED\n\n");
 
+    if ((NULL != gpphLlcNfc_Ctxt) && (TimerId ==
+        gpphLlcNfc_Ctxt->s_timerinfo.timer_id[PH_LLCNFC_ACKTIMER])
+        && (PH_LLCNFC_ACK_TO_BIT_VAL ==
+        (gpphLlcNfc_Ctxt->s_timerinfo.timer_flag &
+        PH_LLCNFC_ACK_TO_BIT_VAL)))
+    {
+        ps_frame_info = &(gpphLlcNfc_Ctxt->s_frameinfo);
+        ps_timer_info = &(gpphLlcNfc_Ctxt->s_timerinfo);
+
+        phLlcNfc_StopTimers (PH_LLCNFC_ACKTIMER, 0);
+
+        if (NFCSTATUS_BUSY == PHNFCSTATUS (ps_frame_info->write_status))
+        {
+            /* Any how write cannot be done and some frame is ready to be sent
+            so this frame will act as the ACK */
+            result = phLlcNfc_H_WriteWaitCall (gpphLlcNfc_Ctxt);
+        }
+        else
+        {
+            /* Create S frame */
+            (void)phLlcNfc_H_CreateSFramePayload (ps_frame_info, &(s_packet_info), phLlcNfc_e_rr);
+
+            result = phLlcNfc_Interface_Write(gpphLlcNfc_Ctxt,
+                        (uint8_t *)&(s_packet_info.s_llcbuf),
+                        (uint32_t)(s_packet_info.llcbuf_len));
+
+            if (NFCSTATUS_PENDING == result)
+            {
+                if (0 == ps_frame_info->send_error_count)
+                {
+                    ps_frame_info->write_wait_call = invalid_frame;
+                }
+                ps_frame_info->sent_frame_type = s_frame;
+            }
+            else
+            {
+                if (invalid_frame == ps_frame_info->write_wait_call)
+                {
+                    ps_frame_info->write_wait_call = s_frame;
+                }
+            }
+        }
+    }
+
+    /* ACK is sent, so reset the response received count */
+    gpphLlcNfc_Ctxt->s_frameinfo.resp_recvd_count = 0;
+
+    PH_LLCNFC_PRINT("\n\nLLC : ACK TIMEOUT CB END\n\n");
 }
-#endif
+
+#endif /* #ifdef PIGGY_BACK */
 
 static 
 void 
@@ -805,7 +902,7 @@ phLlcNfc_ConnectionTimeoutCb (
     void                        *p_upperctxt = NULL;
     phLlcNfc_Frame_t            *ps_frame_info = NULL;
     phLlcNfc_Timerinfo_t        *ps_timer_info = NULL;
-    PHNFC_UNUSED_VARIABLE(pContext);
+    phLlcNfc_LlcPacket_t        s_packet_info;
     
     PH_LLCNFC_PRINT("\n\nLLC : CONNECTION TIMEOUT CB CALLED\n\n");
     if ((NULL != gpphLlcNfc_Ctxt) && (TimerId == 
@@ -834,16 +931,16 @@ phLlcNfc_ConnectionTimeoutCb (
                 {
                     /* Create a U frame */
                     result = phLlcNfc_H_CreateUFramePayload(gpphLlcNfc_Ctxt, 
-                                        &(ps_frame_info->s_llcpacket),
-                                        &(ps_frame_info->s_llcpacket.llcbuf_len), 
+                                        &(s_packet_info),
+                                        &(s_packet_info.llcbuf_len),
                                         phLlcNfc_e_rset);
 
                     if (NFCSTATUS_SUCCESS == result)
                     {
                         /* Call DAL write */
                         result = phLlcNfc_Interface_Write (gpphLlcNfc_Ctxt, 
-                                (uint8_t*)&(ps_frame_info->s_llcpacket.s_llcbuf), 
-                                (uint32_t)(ps_frame_info->s_llcpacket.llcbuf_len));
+                                (uint8_t*)&(s_packet_info.s_llcbuf),
+                                (uint32_t)(s_packet_info.llcbuf_len));
                     }
                     if (NFCSTATUS_PENDING == result)
                     {
diff --git a/src/phLlcNfc_Timer.h b/src/phLlcNfc_Timer.h
index d8f702a..f212a32 100644
--- a/src/phLlcNfc_Timer.h
+++ b/src/phLlcNfc_Timer.h
@@ -56,6 +56,12 @@
 /**< 0x05 Timer for guard time out value */
 #define PH_LLCNFC_GUARD_TO_VALUE            LINK_GUARD_TIMEOUT
 
+#ifdef PIGGY_BACK
+
+#define PH_LLCNFC_ACK_TO_VALUE              LINK_ACK_TIMEOUT
+
+#endif /* #ifdef PIGGY_BACK */
+
 #ifdef LLC_RESET_DELAY
     #define LLC_URSET_DELAY_TIME_OUT        LLC_RESET_DELAY
 #else
@@ -201,8 +207,10 @@ phLlcNfc_DeleteTimer (void);
 
 void 
 phLlcNfc_URSET_Delay_Notify (
-    uint32_t            delay_id,
-    void                *pContext);
+
+    uint32_t            delay_id);
+
+
 
 #endif /* #ifdef LLC_URSET_NO_DELAY */