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diff --git a/peripherals/twi/twi.h b/peripherals/twi/twi.h
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+/* ----------------------------------------------------------------------------
+ *         ATMEL Microcontroller Software Support
+ * ----------------------------------------------------------------------------
+ * Copyright (c) 2008, Atmel Corporation
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the disclaimer below.
+ *
+ * Atmel's name may not be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
+ * DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+ * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ----------------------------------------------------------------------------
+ */
+
+//------------------------------------------------------------------------------
+/// \unit
+///
+/// !Purpose
+///
+/// Interface for configuration the Two Wire Interface (TWI) peripheral.
+///
+/// !Usage
+///
+/// -# Configures a TWI peripheral to operate in master mode, at the given
+/// frequency (in Hz) using TWI_ConfigureMaster().
+/// -# or if hardware possible, configures a TWI peripheral to operate in 
+/// slave mode, at the given frequency (in Hz) using TWI_ConfigureSlave().
+/// -# Sends a STOP condition on the TWI using TWI_Stop().
+/// -# Starts a read operation on the TWI bus with the specified slave using
+/// TWI_StartRead(). Data must then be read using TWI_ReadByte() whenever 
+/// a byte is available (poll using TWI_ByteReceived()).
+/// -# Starts a write operation on the TWI to access the selected slave using
+/// TWI_StartWrite(). A byte of data must be provided to start the write;
+/// other bytes are written next. 
+/// -# Sends a byte of data to one of the TWI slaves on the bus using TWI_WriteByte().
+/// This function must be called once before TWI_StartWrite() with the first byte of data
+/// to send, then it shall be called repeatedly after that to send the remaining bytes.
+/// -# Check if a byte has been received and can be read on the given TWI
+/// peripheral using TWI_ByteReceived(). 
+/// Check if a byte has been sent using TWI_ByteSent().
+/// -# Check if the current transmission is complete (the STOP has been sent)
+/// using TWI_TransferComplete().
+/// -# Enables & disable the selected interrupts sources on a TWI peripheral
+/// using TWI_EnableIt() and TWI_DisableIt().
+/// -# Get current status register of the given TWI peripheral using
+/// TWI_GetStatus(). Get current status register of the given TWI peripheral, but
+/// masking interrupt sources which are not currently enabled using 
+/// TWI_GetMaskedStatus().
+//------------------------------------------------------------------------------
+
+#ifndef TWI_H
+#define TWI_H
+
+//------------------------------------------------------------------------------
+//         Headers
+//------------------------------------------------------------------------------
+
+#include <board.h>
+
+//------------------------------------------------------------------------------
+//         Global definitions
+//------------------------------------------------------------------------------
+
+// Missing AT91C_TWI_TXRDY definition.
+#ifndef AT91C_TWI_TXRDY
+    #define AT91C_TWI_TXRDY   AT91C_TWI_TXRDY_MASTER
+#endif
+
+// Missing AT91C_TWI_TXCOMP definition.
+#ifndef AT91C_TWI_TXCOMP
+    #define AT91C_TWI_TXCOMP  AT91C_TWI_TXCOMP_MASTER
+#endif
+
+//------------------------------------------------------------------------------
+//         Global macros
+//------------------------------------------------------------------------------
+
+/// Returns 1 if the TXRDY bit (ready to transmit data) is set in the given
+/// status register value.
+#define TWI_STATUS_TXRDY(status) ((status & AT91C_TWI_TXRDY) == AT91C_TWI_TXRDY)
+
+/// Returns 1 if the RXRDY bit (ready to receive data) is set in the given
+/// status register value.
+#define TWI_STATUS_RXRDY(status) ((status & AT91C_TWI_RXRDY) == AT91C_TWI_RXRDY)
+
+/// Returns 1 if the TXCOMP bit (transfer complete) is set in the given
+/// status register value.
+#define TWI_STATUS_TXCOMP(status) ((status & AT91C_TWI_TXCOMP) == AT91C_TWI_TXCOMP)
+
+//------------------------------------------------------------------------------
+//         Global functions
+//------------------------------------------------------------------------------
+
+extern void TWI_ConfigureMaster(AT91S_TWI *pTwi, unsigned int twck, unsigned int mck);
+
+#ifdef AT91C_TWI_SVEN  // TWI slave
+extern void TWI_ConfigureSlave(AT91S_TWI *pTwi, unsigned char slaveAddress);
+#endif
+
+extern void TWI_Stop(AT91S_TWI *pTwi);
+
+extern void TWI_StartRead(
+    AT91S_TWI *pTwi,
+    unsigned char address,
+    unsigned int iaddress,
+    unsigned char isize);
+
+extern unsigned char TWI_ReadByte(AT91S_TWI *pTwi);
+
+extern void TWI_WriteByte(AT91S_TWI *pTwi, unsigned char byte);
+
+extern void TWI_StartWrite(
+    AT91S_TWI *pTwi,
+    unsigned char address,
+    unsigned int iaddress,
+    unsigned char isize,
+    unsigned char byte);
+
+extern unsigned char TWI_ByteReceived(AT91S_TWI *pTwi);
+
+extern unsigned char TWI_ByteSent(AT91S_TWI *pTwi);
+
+extern unsigned char TWI_TransferComplete(AT91S_TWI *pTwi);
+
+extern void TWI_EnableIt(AT91S_TWI *pTwi, unsigned int sources);
+
+extern void TWI_DisableIt(AT91S_TWI *pTwi, unsigned int sources);
+
+extern unsigned int TWI_GetStatus(AT91S_TWI *pTwi);
+
+extern unsigned int TWI_GetMaskedStatus(AT91S_TWI *pTwi);
+
+extern void TWI_SendSTOPCondition(AT91S_TWI *pTwi);
+
+#endif //#ifndef TWI_H