Update I2C Slave for lpc812

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.

Author: Willem23

libraries/mbed/common/I2CSlave.cpp

@@ -43,15 +43,33 @@ int I2CSlave::read(char *data, int length) {
 }
 
 int I2CSlave::read(void) {
+// 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.
+//
+//#if defined (TARGET_LPC812) || defined (TARGET_LPC824) || defined (TARGET_LPC1549)
+#if defined (TARGET_LPC812)
+    return i2c_slave_byte_read(&_i2c, 0);
+#else        
     return i2c_byte_read(&_i2c, 0);
+#endif    
 }
 
 int I2CSlave::write(const char *data, int length) {
     return i2c_slave_write(&_i2c, data, length) != length;
 }
 
 int I2CSlave::write(int data) {
+// 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.
+//
+//#if defined (TARGET_LPC812) || defined (TARGET_LPC824) || defined (TARGET_LPC1549)
+#if defined (TARGET_LPC812)
+    return i2c_slave_byte_write(&_i2c, data);    
+#else    
     return i2c_byte_write(&_i2c, data);
+#endif    
 }
 
 void I2CSlave::stop(void) {