diff --git a/firmware/libboard/simtrace/include/board.h b/firmware/libboard/simtrace/include/board.h
index 742ce7c..3b8296b 100644
--- a/firmware/libboard/simtrace/include/board.h
+++ b/firmware/libboard/simtrace/include/board.h
@@ -11,7 +11,7 @@
 /** Phone (SIM card emulator)/CCID Reader/MITM configuration    **/
 /*  Normally the communication lines between phone and SIM card are disconnected    */
 // Disconnect SIM card I/O, VPP line from the phone lines
-// FIXME: Per default pins are input, therefore high-impedance, therefore they don not activate the bus switch, right?
+// FIXME: Per default pins are input, therefore high-impedance, therefore the bus switch is in an unknown state by default for hardware version <= 1.4. It should be pulled high by an external resistor to set the bus switch to high-impedance (e.g. off).
 #define PIN_SC_SW_DEFAULT               {PIO_PA20, PIOA, ID_PIOA, PIO_OUTPUT_1, PIO_DEFAULT}
 // Disconnect SIM card RST, CLK line from the phone lines
 #define PIN_IO_SW_DEFAULT               {PIO_PA19, PIOA, ID_PIOA, PIO_OUTPUT_1, PIO_DEFAULT}
@@ -82,7 +82,7 @@
 #define BOARD_DFU_USB_PRODUCT_ID USB_PRODUCT_SIMTRACE2_DFU
 #define BOARD_USB_RELEASE	0x000
 
-//#define HAVE_SNIFFER
+#define HAVE_SNIFFER
 #define HAVE_CCID
 #define HAVE_CARDEM
 //#define HAVE_MITM
diff --git a/firmware/libcommon/source/sniffer.c b/firmware/libcommon/source/sniffer.c
index 67c11a2..06edb22 100644
--- a/firmware/libcommon/source/sniffer.c
+++ b/firmware/libcommon/source/sniffer.c
@@ -27,14 +27,15 @@
  * ----------------------------------------------------------------------------
  */
 
+#include "board.h"
+#include "simtrace.h"
+
 #ifdef HAVE_SNIFFER
 
 /*------------------------------------------------------------------------------
  *          Headers
  *------------------------------------------------------------------------------*/
 
-#include "board.h"
-
 #include <string.h>
 
 /*------------------------------------------------------------------------------
@@ -67,6 +68,12 @@
 	.state = USART_RCV,
 };
 
+
+int check_data_from_phone(void)
+{
+	TRACE_INFO("check data from phone\n\r");
+}
+
 /*-----------------------------------------------------------------------------
  *          Initialization routine
  *-----------------------------------------------------------------------------*/
@@ -74,22 +81,22 @@
 /* Called during USB enumeration after device is enumerated by host */
 void Sniffer_configure(void)
 {
-	TRACE_INFO("Sniffer config\n");
+	TRACE_INFO("Sniffer config\n\r");
 }
 
 /* called when *different* configuration is set by host */
 void Sniffer_exit(void)
 {
-	TRACE_INFO("Sniffer exit\n");
+	TRACE_INFO("Sniffer exit\n\r");
 	USART_DisableIt(USART_PHONE, US_IER_RXRDY);
 	NVIC_DisableIRQ(USART1_IRQn);
 	USART_SetReceiverEnabled(USART_PHONE, 0);
 }
 
-/* called when *CCID* configuration is set by host */
+/* called when *Sniffer* configuration is set by host */
 void Sniffer_init(void)
 {
-	TRACE_INFO("Sniffer Init\n");
+	TRACE_INFO("Sniffer Init\n\r");
 	/*  Configure ISO7816 driver */
 	PIO_Configure(pinsISO7816_sniff, PIO_LISTSIZE(pinsISO7816_sniff));
 	PIO_Configure(pins_bus, PIO_LISTSIZE(pins_bus));