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+#ifndef _I2CMASTER_H
+#define _I2CMASTER_H 1
+/*************************************************************************
+* Title: C include file for the I2C master interface
+* (i2cmaster.S or twimaster.c)
+* Author: Peter Fleury <pfleury@gmx.ch> http://jump.to/fleury
+* File: $Id: i2cmaster.h,v 1.10 2005/03/06 22:39:57 Peter Exp $
+* Software: AVR-GCC 3.4.3 / avr-libc 1.2.3
+* Target: any AVR device
+* Usage: see Doxygen manual
+**************************************************************************/
+
+#ifdef DOXYGEN
+/**
+ @defgroup pfleury_ic2master I2C Master library
+ @code #include <i2cmaster.h> @endcode
+
+ @brief I2C (TWI) Master Software Library
+
+ Basic routines for communicating with I2C slave devices. This single master
+ implementation is limited to one bus master on the I2C bus.
+
+ This I2c library is implemented as a compact assembler software implementation of the I2C protocol
+ which runs on any AVR (i2cmaster.S) and as a TWI hardware interface for all AVR with built-in TWI hardware (twimaster.c).
+ Since the API for these two implementations is exactly the same, an application can be linked either against the
+ software I2C implementation or the hardware I2C implementation.
+
+ Use 4.7k pull-up resistor on the SDA and SCL pin.
+
+ Adapt the SCL and SDA port and pin definitions and eventually the delay routine in the module
+ i2cmaster.S to your target when using the software I2C implementation !
+
+ Adjust the CPU clock frequence F_CPU in twimaster.c or in the Makfile when using the TWI hardware implementaion.
+
+ @note
+ The module i2cmaster.S is based on the Atmel Application Note AVR300, corrected and adapted
+ to GNU assembler and AVR-GCC C call interface.
+ Replaced the incorrect quarter period delays found in AVR300 with
+ half period delays.
+
+ @author Peter Fleury pfleury@gmx.ch http://jump.to/fleury
+
+ @par API Usage Example
+ The following code shows typical usage of this library, see example test_i2cmaster.c
+
+ @code
+
+ #include <i2cmaster.h>
+
+
+ #define Dev24C02 0xA2 // device address of EEPROM 24C02, see datasheet
+
+ int main(void)
+ {
+ unsigned char ret;
+
+ i2c_init(); // initialize I2C library
+
+ // write 0x75 to EEPROM address 5 (Byte Write)
+ i2c_start_wait(Dev24C02+I2C_WRITE); // set device address and write mode
+ i2c_write(0x05); // write address = 5
+ i2c_write(0x75); // write value 0x75 to EEPROM
+ i2c_stop(); // set stop conditon = release bus
+
+
+ // read previously written value back from EEPROM address 5
+ i2c_start_wait(Dev24C02+I2C_WRITE); // set device address and write mode
+
+ i2c_write(0x05); // write address = 5
+ i2c_rep_start(Dev24C02+I2C_READ); // set device address and read mode
+
+ ret = i2c_readNak(); // read one byte from EEPROM
+ i2c_stop();
+
+ for(;;);
+ }
+ @endcode
+
+*/
+#endif /* DOXYGEN */
+
+/**@{*/
+
+#if (__GNUC__ * 100 + __GNUC_MINOR__) < 304
+#error "This library requires AVR-GCC 3.4 or later, update to newer AVR-GCC compiler !"
+#endif
+
+#include <avr/io.h>
+
+/** defines the data direction (reading from I2C device) in i2c_start(),i2c_rep_start() */
+#define I2C_READ 1
+
+/** defines the data direction (writing to I2C device) in i2c_start(),i2c_rep_start() */
+#define I2C_WRITE 0
+
+
+/**
+ @brief initialize the I2C master interace. Need to be called only once
+ @param void
+ @return none
+ */
+void i2c_init(void);
+
+
+/**
+ @brief Terminates the data transfer and releases the I2C bus
+ @param void
+ @return none
+ */
+void i2c_stop(void);
+
+
+/**
+ @brief Issues a start condition and sends address and transfer direction
+
+ @param addr address and transfer direction of I2C device
+ @retval 0 device accessible
+ @retval 1 failed to access device
+ */
+unsigned char i2c_start(unsigned char addr);
+
+
+/**
+ @brief Issues a repeated start condition and sends address and transfer direction
+
+ @param addr address and transfer direction of I2C device
+ @retval 0 device accessible
+ @retval 1 failed to access device
+ */
+unsigned char i2c_rep_start(unsigned char addr);
+
+
+/**
+ @brief Issues a start condition and sends address and transfer direction
+
+ If device is busy, use ack polling to wait until device ready
+ @param addr address and transfer direction of I2C device
+ @return none
+ */
+void i2c_start_wait(unsigned char addr);
+
+
+/**
+ @brief Send one byte to I2C device
+ @param data byte to be transfered
+ @retval 0 write successful
+ @retval 1 write failed
+ */
+unsigned char i2c_write(unsigned char data);
+
+
+/**
+ @brief read one byte from the I2C device, request more data from device
+ @return byte read from I2C device
+ */
+unsigned char i2c_readAck(void);
+
+/**
+ @brief read one byte from the I2C device, read is followed by a stop condition
+ @return byte read from I2C device
+ */
+unsigned char i2c_readNak(void);
+
+/**
+ @brief read one byte from the I2C device
+
+ Implemented as a macro, which calls either i2c_readAck or i2c_readNak
+
+ @param ack 1 send ack, request more data from device<br>
+ 0 send nak, read is followed by a stop condition
+ @return byte read from I2C device
+ */
+unsigned char i2c_read(unsigned char ack);
+#define i2c_read(ack) (ack) ? i2c_readAck() : i2c_readNak();
+
+
+/**@}*/
+#endif