diff --git a/ADF7021.cpp b/ADF7021.cpp
index 161e643..6e440c5 100644
--- a/ADF7021.cpp
+++ b/ADF7021.cpp
@@ -34,6 +34,31 @@ volatile uint32_t  AD7021_control_word;
 uint32_t           ADF7021_RX_REG0;
 uint32_t           ADF7021_TX_REG0;
 
+volatile bool sle_request = false;
+
+static  void Send_AD7021_control_shift()
+{
+  int AD7021_counter;
+
+  for(AD7021_counter = 31; AD7021_counter >= 0; AD7021_counter--) {
+    if(bitRead(AD7021_control_word, AD7021_counter) == HIGH)
+      io.SDATA_pin(HIGH);
+    else
+      io.SDATA_pin(LOW);
+
+    io.dlybit();
+    io.SCLK_pin(HIGH);
+    io.dlybit();
+    io.SCLK_pin(LOW);
+  }
+}
+
+static  void Send_AD7021_control_nosle()
+{
+  Send_AD7021_control_shift();
+  sle_request = true;
+}
+
 void Send_AD7021_control()
 {
   int AD7021_counter;
@@ -391,7 +416,7 @@ void CIO::setTX()
 { 
   // Send register 0 for TX operation
   AD7021_control_word = ADF7021_TX_REG0;         
-  Send_AD7021_control();
+  Send_AD7021_control_nosle();
   
 #if defined(BIDIR_DATA_PIN)
   Data_dir_out(true);  // Data pin output mode
diff --git a/IO.cpp b/IO.cpp
index 7037241..9524aec 100644
--- a/IO.cpp
+++ b/IO.cpp
@@ -29,6 +29,9 @@ uint32_t    m_frequency_rx;
 uint32_t    m_frequency_tx;
 uint8_t     m_power;
 
+extern volatile bool sle_request;
+static volatile bool sle_pin = 0;
+
 CIO::CIO():
 m_started(false),
 m_rxBuffer(RX_RINGBUFFER_SIZE),
@@ -152,7 +155,25 @@ void CIO::interrupt()
   if (!m_started)
     return;
 
-  if(m_tx) {
+  if (sle_request == true && m_tx)
+  { 
+    if(CLK_pin() == 0)
+    {
+	sle_pin = 1;
+  	SLE_pin(HIGH);
+   }
+   else if (sle_pin == 1)
+   {
+  	SLE_pin(LOW);
+  	SDATA_pin(LOW);
+  	sle_request = false;
+        sle_pin = 0;
+    }
+  }
+
+
+  // we set the TX bit at TXD low, sampling of ADF7021 happens at rising clock
+  if (CLK_pin() == 0 && m_tx ) {
     m_txBuffer.get(bit);
 
 #if defined(BIDIR_DATA_PIN)
@@ -166,8 +187,9 @@ void CIO::interrupt()
     else
       TXD_pin(LOW);
 #endif
-
-  } else {
+  } 
+  // we sample the RX bit at rising TXD clock edge, so TXD must be 1 and we are not in tx mode
+  else if (CLK_pin() == 1 && !m_tx) {
     if(RXD_pin())
       bit = 1;
     else
@@ -176,6 +198,7 @@ void CIO::interrupt()
     m_rxBuffer.put(bit);
   }
 
+
   m_watchdog++;
   m_modeTimerCnt++;
 
@@ -241,6 +264,8 @@ void CIO::write(uint8_t* data, uint16_t length)
   if (!m_tx) {
     setTX();
     m_tx = true;
+    sle_pin = 0;
+    while (sle_request) { asm("nop"); }
   }
 
 }
diff --git a/IO.h b/IO.h
index 1f5ceb5..c635f0d 100644
--- a/IO.h
+++ b/IO.h
@@ -55,6 +55,7 @@ public:
   void     SLE_pin(bool on);
   void     CE_pin(bool on);
   bool     RXD_pin(void);
+  bool     CLK_pin(void);
   
 #if defined(BIDIR_DATA_PIN)
   void     RXD_pin_write(bool on);
diff --git a/IOArduino.cpp b/IOArduino.cpp
index 8497def..c891bc5 100644
--- a/IOArduino.cpp
+++ b/IOArduino.cpp
@@ -171,17 +171,17 @@ void CIO::startInt()
 
 // TXD pin is TxRxCLK of ADF7021, standard TX/RX data interface
 #if defined (__STM32F1__)
-  attachInterrupt(PIN_TXD, EXT_IRQHandler, RISING);
+  attachInterrupt(PIN_TXD, EXT_IRQHandler, CHANGE);
 #else
-  attachInterrupt(digitalPinToInterrupt(PIN_TXD), EXT_IRQHandler, RISING);
+  attachInterrupt(digitalPinToInterrupt(PIN_TXD), EXT_IRQHandler, CHANGE);
 #endif
 
 #else
 
 #if defined (__STM32F1__)
-  attachInterrupt(PIN_CLKOUT, EXT_IRQHandler, RISING);
+  attachInterrupt(PIN_CLKOUT, EXT_IRQHandler, CHANGE);
 #else
-  attachInterrupt(digitalPinToInterrupt(PIN_CLKOUT), EXT_IRQHandler, RISING);
+  attachInterrupt(digitalPinToInterrupt(PIN_CLKOUT), EXT_IRQHandler, CHANGE);
 #endif
 
 #endif
@@ -228,6 +228,11 @@ bool CIO::RXD_pin()
   return digitalRead(PIN_RXD) == HIGH;
 }
 
+bool CIO::CLK_pin()
+{
+  return digitalRead(PIN_TXD) == HIGH;
+}
+
 #if defined(BIDIR_DATA_PIN)
 void CIO::RXD_pin_write(bool on)
 {
@@ -237,7 +242,11 @@ void CIO::RXD_pin_write(bool on)
 
 void CIO::TXD_pin(bool on) 
 {
+#if defined(BIDIR_DATA_PIN)
   digitalWrite(PIN_TXD, on ? HIGH : LOW);
+#else
+  digitalWrite(PIN_CLKOUT, on ? HIGH : LOW);
+#endif
 }
 
 void CIO::LED_pin(bool on) 
diff --git a/IOSTM.cpp b/IOSTM.cpp
index 2cbc3fc..b66fa76 100644
--- a/IOSTM.cpp
+++ b/IOSTM.cpp
@@ -440,7 +440,7 @@ void CIO::Init()
 #endif
 
   EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
-  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
+  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising_Falling;
   EXTI_InitStructure.EXTI_LineCmd = ENABLE;
   EXTI_Init(&EXTI_InitStructure);
 }
@@ -465,7 +465,7 @@ void CIO::startInt()
 
 #endif
 
-  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 15;
+  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 15;
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
   NVIC_Init(&NVIC_InitStructure);
@@ -519,6 +519,15 @@ bool CIO::RXD_pin()
   return GPIO_ReadInputDataBit(PORT_RXD, PIN_RXD) == Bit_SET;
 }
 
+bool CIO::CLK_pin()
+{
+#if defined(BIDIR_DATA_PIN)
+  return GPIO_ReadInputDataBit(PORT_TXD, PIN_TXD) == Bit_SET;
+#else
+  return GPIO_ReadInputDataBit(PORT_CLKOUT, PIN_CLKOUT) == Bit_SET;
+#endif
+}
+
 #if defined(BIDIR_DATA_PIN)
 void CIO::RXD_pin_write(bool on)
 {