diff --git a/sam3s_example/simtrace/simtrace.h b/sam3s_example/simtrace/simtrace.h
index 5e836052..c564563d 100644
--- a/sam3s_example/simtrace/simtrace.h
+++ b/sam3s_example/simtrace/simtrace.h
@@ -1,6 +1,19 @@
 #ifndef SIMTRACE_H
 #define SIMTRACE_H
 
+/* Endpoint numbers */
+#define DATAOUT     1
+#define DATAIN      2
+#define INT         3
+
+#define BUFLEN  64
+typedef struct ring_buffer
+{
+    uint8_t     buf[BUFLEN*2];   // data buffer
+    uint8_t     idx;                // number of items in the buffer
+} ring_buffer;
+
+
 enum confNum {
     CFG_NUM_SNIFF = 1, CFG_NUM_PHONE, CFG_NUM_MITM, NUM_CONF
 };
diff --git a/sam3s_example/simtrace/simtrace_iso7816.c b/sam3s_example/simtrace/simtrace_iso7816.c
index b03c6cdc..2d0b8c7a 100644
--- a/sam3s_example/simtrace/simtrace_iso7816.c
+++ b/sam3s_example/simtrace/simtrace_iso7816.c
@@ -38,11 +38,38 @@
 extern uint8_t rcvdChar;
 extern uint32_t char_stat;
 
+//#define BUFLEN  14
+// FIXME: Remove:
+#define PR TRACE_DEBUG
+//#define PR printf 
+
+/*typedef struct ring_buffer
+{
+    uint8_t     buf[BUFLEN*2];   // data buffer
+    uint8_t     idx;                // number of items in the buffer
+} ring_buffer;
+*/
+ring_buffer buf = { {0}, 0 };
+
+void buf_push(uint8_t item)
+{
+    buf.buf[buf.idx % (BUFLEN*2)] = item;
+    PR("----- Push: %x %x\n\r", buf.idx, buf.buf[buf.idx]);
+    buf.idx = (buf.idx+1) % (BUFLEN*2);
+}
+
+uint8_t get_buf_start(uint8_t *buf_start)
+{
+    *buf_start = &(buf.buf[buf.idx]);
+    return 2*BUFLEN-buf.idx;
+}
+
 /** Initializes a ISO driver
  */ 
 // FIXME: This function is implemented in iso7816_4.c !! Only MCK instead of SCK is always taken. Change that!                                                                               
 void _ISO7816_Init( void )
 {   
+    printf("ISO_Init\n\r");
     TRACE_DEBUG("ISO_Init\n\r");
                         
     USART_Configure( USART_PHONE,                                                          
@@ -98,20 +125,29 @@ void USART1_IrqHandler( void )
 */  
     uint32_t csr = USART_PHONE->US_CSR;                                                       
     
+    PR("---- stat: %x\n\r", csr);
+
     if (csr & US_CSR_TXRDY) {
         /* transmit buffer empty, nothing to transmit */                                      
     }  
     if (csr & US_CSR_RXRDY) {
         stat = (csr&(US_CSR_OVRE|US_CSR_FRAME|
-                        US_CSR_PARE|US_CSR_TIMEOUT|US_CSR_NACK|                               
-                        (1<<10)));                                                            
-        
+                        US_CSR_PARE|US_CSR_TIMEOUT|US_CSR_NACK|
+                        (1<<10)));
+
         if (stat == 0 ) {
-            /* Get a char */
-            rcvdChar = ((USART_PHONE->US_RHR) & 0xFF);                                        
-        } /* else: error occured */                                                           
-        char_stat = stat;                                                                     
-    }                                                                                         
-}                                                                                             
+            /* Fill char into buffer */
+            PR("---- BUFLEN %x\n\r", buf.idx);
+            buf_push((USART_PHONE->US_RHR) & 0xFF);
+        } else {
+       //     buf_push((USART_PHONE->US_RHR) & 0xFF);
+            PR("%x\n\r", (USART_PHONE->US_RHR) & 0xFF);
+        } /* else: error occured */
 
+        if ((buf.idx % BUFLEN) == 0) {
+            rcvdChar = 1;
+        }
 
+        char_stat = stat;
+    }
+}
diff --git a/sam3s_example/simtrace/sniffer.c b/sam3s_example/simtrace/sniffer.c
index 46545263..c7182028 100644
--- a/sam3s_example/simtrace/sniffer.c
+++ b/sam3s_example/simtrace/sniffer.c
@@ -38,6 +38,8 @@
 /*------------------------------------------------------------------------------
  *         Internal definitions
  *------------------------------------------------------------------------------*/
+// FIXME: Remove:
+#define PR TRACE_DEBUG
 
 /** Maximum ucSize in bytes of the smartcard answer to a command.*/
 #define MAX_ANSWER_SIZE         10
@@ -60,6 +62,7 @@ static const Pin pPwr[] = {
 
 extern uint32_t char_stat;
 extern uint8_t rcvdChar;
+extern ring_buffer buf;
 
 /*-----------------------------------------------------------------------------
  *          Initialization routine
@@ -80,8 +83,16 @@ void Sniffer_Init( void )
 
 void Sniffer_run( void )
 {
+    uint8_t c = 0;
+    c++;
+
     if (rcvdChar != 0) {
-        TRACE_DEBUG("Rcvd char _%x_ \n\r", rcvdChar);
+        /*  DATA_IN for host side is data_out for simtrace side   */
+        /* FIXME: Performancewise sending a USB packet for every byte is a disaster */
+        PR("----- %x %x %x ..\n\r", buf.buf[0], buf.buf[1],buf.buf[2] );
+        USBD_Write( DATAIN, buf.buf, BUFLEN, 0, 0 );
+//        USBD_Write( DATAIN, &c, 1, 0, 0 );
+        PR("----- Rcvd char\n\r");
         rcvdChar = 0;
     }
 }
diff --git a/sam3s_example/simtrace/usb.c b/sam3s_example/simtrace/usb.c
index 39893d8b..606b0b48 100644
--- a/sam3s_example/simtrace/usb.c
+++ b/sam3s_example/simtrace/usb.c
@@ -154,11 +154,6 @@ const unsigned char *stringDescriptors[] = {
     MITMConfigStringDescriptor
 };
 
-/* Endpoint numbers */
-#define DATAOUT     1
-#define DATAIN      2
-#define INT         3
-
 /*------------------------------------------------------------------------------
  *       USB Device descriptors 
  *------------------------------------------------------------------------------*/