How to use I2C / TWI (Two Wire Interface) in AVR ATmega32- (Part 36/46)

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// Program for Master Mode
// Check Code2 for Slave Mode Program
#include<avr/io.h>
#include<util/delay.h>
#include<inttypes.h>
 
void TWI_start(void);
void TWI_repeated_start(void);
void TWI_init_master(void);
void TWI_write_address(unsigned char);
void TWI_read_address(unsigned char);
void TWI_write_data(unsigned char);
void TWI_read_data(void);
void TWI_stop(void);
 
unsigned char address=0x20, read=1, write=0;
unsigned char write_data=0x01, recv_data;
 
int main(void)
{
_delay_ms(2000);
DDRB=0xff;
TWI_init_master();  // Function to initialize TWI
while(1)
{
if(write_data==0x00) 
write_data=1;
 
TWI_start(); // Function to send start condition
TWI_write_address(address+write); // Function to write address and data direction bit(write) on SDA
TWI_write_data(write_data);      // Function to write data in slave
TWI_stop(); // Function to send stop condition
 
 
_delay_ms(10); // Delay of 10 mili second
 
TWI_start(); 
TWI_read_address(address+read); // Function to write address and data direction bit(read) on SDA
TWI_read_data(); // Function to read data from slave 
TWI_stop();
 
_delay_ms(1000); 
 
write_data = write_data * 2;
}
 
 
}
 
void TWI_init_master(void) // Function to initialize master
{
TWBR=0x01; // Bit rate
TWSR=(0<<TWPS1)|(0<<TWPS0); // Setting prescalar bits
// SCL freq= F_CPU/(16+2(TWBR).4^TWPS)
}
 
void TWI_start(void)
{
// Clear TWI interrupt flag, Put start condition on SDA, Enable TWI
TWCR= (1<<TWINT)|(1<<TWSTA)|(1<<TWEN); 
while(!(TWCR & (1<<TWINT))); // Wait till start condition is transmitted
while((TWSR & 0xF8)!= 0x08); // Check for the acknowledgement
}
 
void TWI_repeated_start(void)
{
// Clear TWI interrupt flag, Put start condition on SDA, Enable TWI
TWCR= (1<<TWINT)|(1<<TWSTA)|(1<<TWEN); 
while(!(TWCR & (1<<TWINT))); // wait till restart condition is transmitted
while((TWSR & 0xF8)!= 0x10); // Check for the acknoledgement
}
 
void TWI_write_address(unsigned char data)
{
TWDR=data; // Address and write instruction
TWCR=(1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI
while (!(TWCR & (1<<TWINT))); // Wait till complete TWDR byte transmitted
while((TWSR & 0xF8)!= 0x18);  // Check for the acknoledgement
}
 
void TWI_read_address(unsigned char data)
{
TWDR=data; // Address and read instruction
TWCR=(1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI
while (!(TWCR & (1<<TWINT))); // Wait till complete TWDR byte received
while((TWSR & 0xF8)!= 0x40);  // Check for the acknoledgement
}
 
void TWI_write_data(unsigned char data)
{
TWDR=data; // put data in TWDR
TWCR=(1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI
while (!(TWCR & (1<<TWINT))); // Wait till complete TWDR byte transmitted
while((TWSR & 0xF8) != 0x28); // Check for the acknoledgement
}
 
void TWI_read_data(void)
{
TWCR=(1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI
while (!(TWCR & (1<<TWINT))); // Wait till complete TWDR byte transmitted
while((TWSR & 0xF8) != 0x58); // Check for the acknoledgement
recv_data=TWDR;
PORTB=recv_data;
}
  
void TWI_stop(void)
{
// Clear TWI interrupt flag, Put stop condition on SDA, Enable TWI
TWCR= (1<<TWINT)|(1<<TWEN)|(1<<TWSTO); 
while(!(TWCR & (1<<TWSTO)));  // Wait till stop condition is transmitted
}
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// Program for Slave mode
#include<avr/io.h>
#include<util/delay.h>
 
void TWI_init_slave(void);
void TWI_match_read_slave(void);
void TWI_read_slave(void);
void TWI_match_write_slave(void);
void TWI_write_slave(void);
 
unsigned char write_data,recv_data;
 
int main(void)
{
DDRB=0xff;
TWI_init_slave(); // Function to initilaize slave
while(1)
{
TWI_match_read_slave(); //Function to match the slave address and slave dirction bit(read) 
TWI_read_slave(); // Function to read data
 
write_data=~recv_data; // Togglem the receive data
 
TWI_match_write_slave(); //Function to match the slave address and slave dirction bit(write) 
TWI_write_slave();       // Function to write data
}
}
 
void TWI_init_slave(void) // Function to initilaize slave
{
TWAR=0x20; // Fill slave address to TWAR
}
 
void TWI_write_slave(void) // Function to write data
{
TWDR= write_data;           // Fill TWDR register whith the data to be sent 
TWCR= (1<<TWEN)|(1<<TWINT);   // Enable TWI, Clear TWI interrupt flag 
while((TWSR & 0xF8) != 0xC0); // Wait for the acknowledgement
}
 
void TWI_match_write_slave(void) //Function to match the slave address and slave dirction bit(write) 
{
while((TWSR & 0xF8)!= 0xA8) // Loop till correct acknoledgement have been received
{
// Get acknowlegement, Enable TWI, Clear TWI interrupt flag
TWCR=(1<<TWEA)|(1<<TWEN)|(1<<TWINT); 
while (!(TWCR & (1<<TWINT)));  // Wait for TWINT flag
}
}
 
void TWI_read_slave(void)
{
// Clear TWI interrupt flag,Get acknowlegement, Enable TWI
TWCR= (1<<TWINT)|(1<<TWEA)|(1<<TWEN); 
while (!(TWCR & (1<<TWINT))); // Wait for TWINT flag
while((TWSR & 0xF8)!=0x80); // Wait for acknowledgement
recv_data=TWDR; // Get value from TWDR
PORTB=recv_data; // send the receive value on PORTB
}
 
void TWI_match_read_slave(void) //Function to match the slave address and slave dirction bit(read)
{
while((TWSR & 0xF8)!= 0x60)  // Loop till correct acknoledgement have been received
{
// Get acknowlegement, Enable TWI, Clear TWI interrupt flag
TWCR=(1<<TWEA)|(1<<TWEN)|(1<<TWINT); 
while (!(TWCR & (1<<TWINT)));  // Wait for TWINT flag
}
}
 
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• ATmega32
• LED