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I2C_master.c
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I2C_master.c
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#ifndef F_CPU
#define F_CPU 16000000UL
#endif
#include <avr/io.h>
#include <util/twi.h>
#include "I2C_master.h"
#define F_SCL 100000UL // SCL frequency
#define Prescaler 1
#define TWBR_val ((((F_CPU / F_SCL) / Prescaler) - 16 ) / 2)
void I2C_init(void)
{
TWBR = TWBR_val;
}
uint8_t I2C_start(uint8_t address)
{
// reset TWI control register
TWCR = 0;
// transmit START condition
TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
// wait for end of transmission
while( !(TWCR & (1<<TWINT)) );
// check if the start condition was successfully transmitted
if((TWSR & 0xF8) != TW_START)
{
return 1;
}
// load slave address into data register
TWDR = address;
// start transmission of address
TWCR = (1<<TWINT) | (1<<TWEN);
// wait for end of transmission
while( !(TWCR & (1<<TWINT)) );
// check if the device has acknowledged the READ / WRITE mode
uint8_t twst = TW_STATUS & 0xF8;
if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) )
return 1;
return 0;
}
uint8_t I2C_write(uint8_t data)
{
// load data into data register
TWDR = data;
// start transmission of data
TWCR = (1<<TWINT) | (1<<TWEN);
// wait for end of transmission
while( !(TWCR & (1<<TWINT)) );
if( (TWSR & 0xF8) != TW_MT_DATA_ACK )
{
return 1;
}
return 0;
}
uint8_t I2C_read_ack(void)
{
// start TWI module and acknowledge data after reception
TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
// wait for end of transmission
while( !(TWCR & (1<<TWINT)) );
// return received data from TWDR
return TWDR;
}
uint8_t I2C_read_nack(void)
{
// start receiving without acknowledging reception
TWCR = (1<<TWINT) | (1<<TWEN);
// wait for end of transmission
while( !(TWCR & (1<<TWINT)) );
// return received data from TWDR
return TWDR;
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////
/*
Function Name:
I2C_Writer
Input Parameters:
<unsigned 8-bit integer> <Address> <Address of the slave I2C member>
<unsigned 8-bit integer> <Location> <Location in the slave receiver buffer>
<unsigned 8-bit integer> <Data> <Data to be transmitted>
Outputs:
N/A
*/
//////////////////////////////////////////////////////////////////////////////////////////////////////////
void I2C_Writer(uint8_t Address, uint8_t Location, uint8_t Data)
{
I2C_start(Address); //Start an I2C transfer to the requested Target Slave Address
I2C_write(Location); //Write data to the specified location in the Slave's receving buffer
I2C_write(Data); //The data to be written
I2C_stop(); //End the I2C transmition
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////
/*
Function Name:
I2C_Read
Input Parameters:
<unsigned 8-bit integer> <Address> <Address of the slave I2C member>
<unsigned 8-bit integer> <Location> <Location in the slave transmitting buffer>
Outputs:
<unsigned 8-bit integer> <temp> <Data the have been read from slave>
*/
//////////////////////////////////////////////////////////////////////////////////////////////////////////
uint8_t I2C_Reader(uint8_t Address, uint8_t Location)
{
uint8_t temp;
I2C_start(Address);
I2C_write(Location);
I2C_stop();
I2C_start(Address | 0x01);
I2C_read_ack();
temp=I2C_read_nack();
I2C_stop();
return temp;
}
void I2C_stop(void){
// transmit STOP condition
TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
}