diff --git a/Internet/DHCP/dhcp.c b/Internet/DHCP/dhcp.c
index 8969a31..8e21124 100644
--- a/Internet/DHCP/dhcp.c
+++ b/Internet/DHCP/dhcp.c
@@ -56,7 +56,8 @@
 /* If you want to display debug & processing message, Define _DHCP_DEBUG_ in dhcp.h */
 
 #ifdef _DHCP_DEBUG_
-   #include <stdio.h>
+   //#include <stdio.h>
+   int logMsg(const char *format, ...);
 #endif   
 
 /* DHCP state machine. */
@@ -417,7 +418,7 @@ void send_DHCP_DISCOVER(void)
 	ip[3] = 255;
 
 #ifdef _DHCP_DEBUG_
-	printf("> Send DHCP_DISCOVER\r\n");
+	logMsg("> Send DHCP_DISCOVER\r\n");
 #endif
 
 	sendto(DHCP_SOCKET, (uint8_t *)pDHCPMSG, RIP_MSG_SIZE, ip, DHCP_SERVER_PORT);
@@ -515,7 +516,7 @@ void send_DHCP_REQUEST(void)
 	for (i = k; i < OPT_SIZE; i++) pDHCPMSG->OPT[i] = 0;
 
 #ifdef _DHCP_DEBUG_
-	printf("> Send DHCP_REQUEST\r\n");
+	logMsg("> Send DHCP_REQUEST\r\n");
 #endif
 	
 	sendto(DHCP_SOCKET, (uint8_t *)pDHCPMSG, RIP_MSG_SIZE, ip, DHCP_SERVER_PORT);
@@ -576,7 +577,7 @@ void send_DHCP_DECLINE(void)
 	ip[3] = 0xFF;
 
 #ifdef _DHCP_DEBUG_
-	printf("\r\n> Send DHCP_DECLINE\r\n");
+	logMsg("\r\n> Send DHCP_DECLINE\r\n");
 #endif
 
 	sendto(DHCP_SOCKET, (uint8_t *)pDHCPMSG, RIP_MSG_SIZE, ip, DHCP_SERVER_PORT);
@@ -598,7 +599,7 @@ int8_t parseDHCPMSG(void)
    {
    	len = recvfrom(DHCP_SOCKET, (uint8_t *)pDHCPMSG, len, svr_addr, &svr_port);
    #ifdef _DHCP_DEBUG_   
-      printf("DHCP message : %d.%d.%d.%d(%d) %d received. \r\n",svr_addr[0],svr_addr[1],svr_addr[2], svr_addr[3],svr_port, len);
+      logMsg("DHCP message : %d.%d.%d.%d(%d) %d received. \r\n",svr_addr[0],svr_addr[1],svr_addr[2], svr_addr[3],svr_port, len);
    #endif   
    }
    else {
@@ -611,7 +612,7 @@ int8_t parseDHCPMSG(void)
 		     (pDHCPMSG->chaddr[4] != DHCP_CHADDR[4]) || (pDHCPMSG->chaddr[5] != DHCP_CHADDR[5])   )
 		{
 #ifdef _DHCP_DEBUG_
-            printf("No My DHCP Message. This message is ignored.\r\n");
+            logMsg("No My DHCP Message. This message is ignored.\r\n");
 #endif
          return 0;
 		}
@@ -621,7 +622,7 @@ int8_t parseDHCPMSG(void)
                 ((svr_addr[0]!=DHCP_REAL_SIP[0])|| (svr_addr[1]!=DHCP_REAL_SIP[1])|| (svr_addr[2]!=DHCP_REAL_SIP[2])|| (svr_addr[3]!=DHCP_REAL_SIP[3]))  )
             {
 #ifdef _DHCP_DEBUG_
-                printf("Another DHCP sever send a response message. This is ignored.\r\n");
+                logMsg("Another DHCP sever send a response message. This is ignored.\r\n");
 #endif
                 return 0;
             }
@@ -730,7 +731,7 @@ uint8_t DHCP_run(void)
 		case STATE_DHCP_DISCOVER :
 			if (type == DHCP_OFFER){
 #ifdef _DHCP_DEBUG_
-				printf("> Receive DHCP_OFFER\r\n");
+				logMsg("> Receive DHCP_OFFER\r\n");
 #endif
             DHCP_allocated_ip[0] = pDHCPMSG->yiaddr[0];
             DHCP_allocated_ip[1] = pDHCPMSG->yiaddr[1];
@@ -746,7 +747,7 @@ uint8_t DHCP_run(void)
 			if (type == DHCP_ACK) {
 
 #ifdef _DHCP_DEBUG_
-				printf("> Receive DHCP_ACK\r\n");
+				logMsg("> Receive DHCP_ACK\r\n");
 #endif
 				if (check_DHCP_leasedIP()) {
 					// Network info assignment from DHCP
@@ -763,7 +764,7 @@ uint8_t DHCP_run(void)
 			} else if (type == DHCP_NAK) {
 
 #ifdef _DHCP_DEBUG_
-				printf("> Receive DHCP_NACK\r\n");
+				logMsg("> Receive DHCP_NACK\r\n");
 #endif
 
 				reset_DHCP_timeout();
@@ -777,7 +778,7 @@ uint8_t DHCP_run(void)
 			if ((dhcp_lease_time != INFINITE_LEASETIME) && ((dhcp_lease_time/2) < dhcp_tick_1s)) {
 				
 #ifdef _DHCP_DEBUG_
- 				printf("> Maintains the IP address \r\n");
+ 				logMsg("> Maintains the IP address \r\n");
 #endif
 
 				type = 0;
@@ -808,19 +809,19 @@ uint8_t DHCP_run(void)
 					ret = DHCP_IP_CHANGED;
 					dhcp_ip_update();
                #ifdef _DHCP_DEBUG_
-                  printf(">IP changed.\r\n");
+                  logMsg(">IP changed.\r\n");
                #endif
 					
 				}
          #ifdef _DHCP_DEBUG_
-            else printf(">IP is continued.\r\n");
+            else logMsg(">IP is continued.\r\n");
          #endif            				
 				reset_DHCP_timeout();
 				dhcp_state = STATE_DHCP_LEASED;
 			} else if (type == DHCP_NAK) {
 
 #ifdef _DHCP_DEBUG_
-				printf("> Receive DHCP_NACK, Failed to maintain ip\r\n");
+				logMsg("> Receive DHCP_NACK, Failed to maintain ip\r\n");
 #endif
 
 				reset_DHCP_timeout();
@@ -850,18 +851,18 @@ uint8_t check_DHCP_timeout(void)
 
 			switch ( dhcp_state ) {
 				case STATE_DHCP_DISCOVER :
-//					printf("<<timeout>> state : STATE_DHCP_DISCOVER\r\n");
+//					logMsg("<<timeout>> state : STATE_DHCP_DISCOVER\r\n");
 					send_DHCP_DISCOVER();
 				break;
 		
 				case STATE_DHCP_REQUEST :
-//					printf("<<timeout>> state : STATE_DHCP_REQUEST\r\n");
+//					logMsg("<<timeout>> state : STATE_DHCP_REQUEST\r\n");
 
 					send_DHCP_REQUEST();
 				break;
 
 				case STATE_DHCP_REREQUEST :
-//					printf("<<timeout>> state : STATE_DHCP_REREQUEST\r\n");
+//					logMsg("<<timeout>> state : STATE_DHCP_REREQUEST\r\n");
 					
 					send_DHCP_REQUEST();
 				break;
@@ -914,7 +915,7 @@ int8_t check_DHCP_leasedIP(void)
 		// UDP send Timeout occurred : allocated IP address is unique, DHCP Success
 
 #ifdef _DHCP_DEBUG_
-		printf("\r\n> Check leased IP - OK\r\n");
+		logMsg("\r\n> Check leased IP - OK\r\n");
 #endif
 
 		return 1;
diff --git a/Internet/DHCP/dhcp.h b/Internet/DHCP/dhcp.h
index 9a8d5e9..767b0c5 100644
--- a/Internet/DHCP/dhcp.h
+++ b/Internet/DHCP/dhcp.h
@@ -55,7 +55,7 @@ extern "C" {
  * @details If you want to display debug & processing message, Define _DHCP_DEBUG_ 
  * @note    If defined, it depends on <stdio.h>
  */
-//#define _DHCP_DEBUG_
+#define _DHCP_DEBUG_
 
 
 /* Retry to processing DHCP */