diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/i2c_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/i2c_api.c
index 1fa7d11ab7..916242f3bd 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/i2c_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/i2c_api.c
@@ -17,6 +17,8 @@
 #include "cmsis.h"
 #include "pinmap.h"
 
+#if DEVICE_I2C
+
 static const SWM_Map SWM_I2C_SDA[] = {
     {7, 24},
 };
@@ -75,6 +77,10 @@ void i2c_init(i2c_t *obj, PinName sda, PinName scl) {
     i2c_interface_enable(obj);
 }
 
+//Actually Wrong. Spec says: First store Address in DAT before setting STA ! 
+//Undefined state when using single byte I2C operations and too much delay
+//between i2c_start and do_i2c_write(Address).
+//Also note that lpc812 will immediately continue reading a byte when Address b0 == 1
 inline int i2c_start(i2c_t *obj) {
     int status = 0;
     if (repeated_start) {
@@ -86,8 +92,6 @@ inline int i2c_start(i2c_t *obj) {
     return status;
 }
 
-
-
 //Generate Stop condition and wait until bus is Idle
 //Will also send NAK for previous RD
 inline int i2c_stop(i2c_t *obj) {
@@ -95,7 +99,8 @@ inline int i2c_stop(i2c_t *obj) {
 
     obj->i2c->MSTCTL = (1 << 2) | (1 << 0); // STP bit and Continue bit. Sends NAK to complete previous RD
     
-    while ((obj->i2c->STAT & ((7 << 1) | (1 << 0))) != ((0 << 1) | (1 << 0))) { //Spin until Ready (b0 == 1)and Status is Idle (b3..b1 == 000)
+    //Spin until Ready (b0 == 1)and Status is Idle (b3..b1 == 000)
+    while ((obj->i2c->STAT & ((7 << 1) | (1 << 0))) != ((0 << 1) | (1 << 0))) { 
         timeout ++;
         if (timeout > 100000) return 1;
     }
@@ -265,3 +270,244 @@ int i2c_byte_write(i2c_t *obj, int data) {
 
     return ack;
 }
+
+#if DEVICE_I2CSLAVE
+
+#define I2C_SLVDAT(x)        (x->i2c->SLVDAT)
+#define I2C_SLVSTAT(x)      ((x->i2c->STAT >> 9) & (0x03))
+#define I2C_SLVSI(x)        ((x->i2c->STAT >> 8) & (0x01))
+//#define I2C_SLVCNT(x)        (x->i2c->SLVCTL = (1 << 0))
+//#define I2C_SLVNAK(x)        (x->i2c->SLVCTL = (1 << 1))
+
+#if(0)
+// Wait until the Slave Serial Interrupt (SI) is set
+// Timeout when it takes too long.
+static int i2c_wait_slave_SI(i2c_t *obj) {
+    int timeout = 0;
+    while (!(obj->i2c->STAT & (1 << 8))) {
+        timeout++;
+        if (timeout > 100000) return -1;
+    }
+    return 0;
+}
+#endif
+
+void i2c_slave_mode(i2c_t *obj, int enable_slave) {
+
+  if (enable_slave) {
+//    obj->i2c->CFG &= ~(1 << 0); //Disable Master mode    
+    obj->i2c->CFG |=  (1 << 1); //Enable Slave mode
+  }
+  else {
+//    obj->i2c->CFG |=  (1 << 0); //Enable Master mode    
+    obj->i2c->CFG &= ~(1 << 1); //Disable Slave mode
+  } 
+}
+
+// Wait for next I2C event and find out what is going on
+//
+int i2c_slave_receive(i2c_t *obj) {
+  int addr;
+  
+  // Check if there is any data pending
+  if (! I2C_SLVSI(obj)) {
+    return 0; //NoData    
+  };
+  
+  // Check State
+  switch(I2C_SLVSTAT(obj)) {
+    case 0x0: // Slave address plus R/W received 
+              // At least one of the four slave addresses has been matched by hardware.
+              // You can figure out which address by checking Slave address match Index in STAT register.
+               
+              // Get the received address
+              addr = I2C_SLVDAT(obj) & 0xFF;
+              // Send ACK on address and Continue
+              obj->i2c->SLVCTL = (1 << 0); 
+              
+              if (addr == 0x00) {
+                return 2; //WriteGeneral
+              }  
+              //check the RW bit
+              if ((addr & 0x01) == 0x01) {
+                return 1; //ReadAddressed
+              }
+              else {
+                return 3; //WriteAddressed
+              }
+              //break;
+    
+    case 0x1: // Slave receive. Received data is available (Slave Receiver mode).
+              // Oops, should never get here...     
+              obj->i2c->SLVCTL = (1 << 1);  // Send NACK on received data, try to recover...
+              return 0; //NoData        
+              
+    case 0x2: // Slave transmit. Data can be transmitted (Slave Transmitter mode).
+              // Oops, should never get here...         
+              I2C_SLVDAT(obj) = 0xFF;       // Send dummy data for transmission
+              obj->i2c->SLVCTL = (1 << 0);  // Continue and try to recover...
+              return 0; //NoData        
+    
+    case 0x3: // Reserved.
+    default:  // Oops, should never get here... 
+              obj->i2c->SLVCTL = (1 << 0);  // Continue and try to recover...              
+              return 0; //NoData        
+              //break; 
+  } //switch status  
+}
+
+// The dedicated I2C Slave byte read and byte write functions need to be called
+// from 'common' mbed I2CSlave API for devices that have separate Master and 
+// Slave engines such as the lpc812 and lpc1549.
+
+//Called when Slave is addressed for Write, Slave will receive Data in polling mode
+//Parameter last=1 means received byte will be NACKed.
+int i2c_slave_byte_read(i2c_t *obj, int last) {
+  int data;
+  
+  // Wait for data
+  while (!I2C_SLVSI(obj)); // Wait forever
+//if (i2c_wait_slave_SI(obj) != 0) {return -2;} // Wait with timeout
+
+  // Dont bother to check State, were not returning it anyhow..
+//if (I2C_SLVSTAT(obj)) == 0x01) {
+  // Slave receive. Received data is available (Slave Receiver mode).    
+//};
+
+  data = I2C_SLVDAT(obj) & 0xFF; // Get and store the received data
+  if (last) {
+    obj->i2c->SLVCTL = (1 << 1);  // Send NACK on received data and Continue 
+  }    
+  else {  
+    obj->i2c->SLVCTL = (1 << 0);  // Send ACK on data and Continue to read                
+  }
+ 
+  return data; 
+}
+
+
+//Called when Slave is addressed for Read, Slave will send Data in polling mode
+//
+int i2c_slave_byte_write(i2c_t *obj, int data) {
+
+  // Wait until Ready 
+  while (!I2C_SLVSI(obj)); // Wait forever
+//  if (i2c_wait_slave_SI(obj) != 0) {return -2;} // Wait with timeout
+
+  // Check State
+  switch(I2C_SLVSTAT(obj)) {
+    case 0x0: // Slave address plus R/W received 
+              // At least one of the four slave addresses has been matched by hardware.
+              // You can figure out which address by checking Slave address match Index in STAT register.                
+              // I2C Restart occurred
+              return -1; 
+              //break;    
+    case 0x1: // Slave receive. Received data is available (Slave Receiver mode).
+              // Should not get here... 
+              return -2;
+              //break;                
+    case 0x2: // Slave transmit. Data can be transmitted (Slave Transmitter mode).
+              I2C_SLVDAT(obj) = data & 0xFF; // Store the data for transmission
+              obj->i2c->SLVCTL = (1 << 0);   // Continue to send
+              
+              return 1;    
+              //break;      
+    case 0x3: // Reserved.
+    default:
+              // Should not get here... 
+              return -3;
+              //break; 
+  } // switch status
+}
+
+
+//Called when Slave is addressed for Write, Slave will receive Data in polling mode
+//Parameter length (>=1) is the maximum allowable number of bytes. All bytes will be ACKed.
+int i2c_slave_read(i2c_t *obj, char *data, int length) {
+  int count=0;
+  
+  // Read and ACK all expected bytes
+  while (count < length) {
+    // Wait for data
+    while (!I2C_SLVSI(obj)); // Wait forever
+//    if (i2c_wait_slave_SI(obj) != 0) {return -2;} // Wait with timeout
+
+    // Check State
+    switch(I2C_SLVSTAT(obj)) {
+      case 0x0: // Slave address plus R/W received 
+                // At least one of the four slave addresses has been matched by hardware.
+                // You can figure out which address by checking Slave address match Index in STAT register.                
+                // I2C Restart occurred
+                return -1; 
+                //break;
+    
+      case 0x1: // Slave receive. Received data is available (Slave Receiver mode).
+                data[count] = I2C_SLVDAT(obj) & 0xFF; // Get and store the received data
+                obj->i2c->SLVCTL = (1 << 0);          // Send ACK on data and Continue to read                
+                break;
+
+      case 0x2: // Slave transmit. Data can be transmitted (Slave Transmitter mode).
+      case 0x3: // Reserved.
+      default:  // Should never get here... 
+                return -2;
+                //break; 
+    } // switch status
+    
+    count++;
+  } // for all bytes
+    
+  return count; // Received the expected number of bytes
+}
+
+
+//Called when Slave is addressed for Read, Slave will send Data in polling mode
+//Parameter length (>=1) is the maximum number of bytes. Exit when Slave byte is NACKed.
+int i2c_slave_write(i2c_t *obj, const char *data, int length) {
+  int count;
+  
+  // Send and all bytes or Exit on NAK
+  for (count=0; count < length; count++) {
+    // Wait until Ready for data 
+    while (!I2C_SLVSI(obj)); // Wait forever
+//    if (i2c_wait_slave_SI(obj) != 0) {return -2;} // Wait with timeout
+
+    // Check State
+    switch(I2C_SLVSTAT(obj)) {
+      case 0x0: // Slave address plus R/W received 
+                // At least one of the four slave addresses has been matched by hardware.
+                // You can figure out which address by checking Slave address match Index in STAT register.                
+                // I2C Restart occurred
+                return -1; 
+                //break;    
+      case 0x1: // Slave receive. Received data is available (Slave Receiver mode).
+                // Should not get here... 
+                return -2;
+                //break;                
+      case 0x2: // Slave transmit. Data can be transmitted (Slave Transmitter mode).
+                I2C_SLVDAT(obj) = data[count] & 0xFF; // Store the data for transmission
+                obj->i2c->SLVCTL = (1 << 0);          // Continue to send
+                break;      
+      case 0x3: // Reserved.
+      default:
+              // Should not get here... 
+              return -3;
+              //break; 
+    } // switch status
+  } // for all bytes
+     
+  return length; // Transmitted the max number of bytes
+}
+
+
+// Set the four slave addresses. 
+void i2c_slave_address(i2c_t *obj, int idx, uint32_t address, uint32_t mask) {
+  obj->i2c->SLVADR0   = (address & 0xFE); // Store address in address 0 register
+  obj->i2c->SLVADR1   = (0x00    & 0xFE); // Store general call write address in address 1 register
+  obj->i2c->SLVADR2   = (0x01);           // Disable address 2 register
+  obj->i2c->SLVADR3   = (0x01);           // Disable address 3 register
+  obj->i2c->SLVQUAL0  = (mask & 0xFE);    // Qualifier mask for address 0 register. Any maskbit that is 1 will always be a match 
+}
+
+#endif
+
+#endif