TWI_Master.c

/*******************************************************
 Author:					Manfred Langemann
 mailto:					Manfred.Langemann ät t-online.de
 Begin of project:			04.01.2008
 Latest version generated:	04.01.2008
 Filename:					TWI_Master.c
 Description:    			TWI Master functions
 
 Master code adapted form Peter Fleury <pfleury@gmx.ch>
 http://jump.to/fleury
 --------------------------------------------------------
 Program Example
 --------------------------------------------------------
 
 int main (void)
	{
	uint8_t		i=0;
	uint8_t		j=0;
	uint8_t		Data[8];
	uint8_t		SlaveAddress = 15;
 
 // Clear any interrupt
	cli ();
 
 // Wait 1 second for POR
	Delay_ms (1000);
 
 // Initiate RS232
	RS232_Init ();
	printf ("Hello world...\n");
 
 // Initiate TWI Master with bitrate of 100000 Hz
	TWIM_Init (100000);
 
 // Endless loop
	while (1)
 {
 // Read byte(s) from the slave.
 // It is implicitely assumed, that the slave will send
 // 8 bytes.
 if (!TWIM_Start (SlaveAddress, TWIM_READ))
 {
 TWIM_Stop ();
 printf ("Could not start TWI Bus for READ\n");
 }
 else
 {
 for (i=0;i<7;i++)
 {
 Data[i] = TWIM_ReadAck ();
 }
 Data[7] = TWIM_ReadNack ();
 printf ("Reading Byte %d: %d\n", i, Data[i]);
 TWIM_Stop ();
 Delay_ms (1000);
 }
 
 // Write byte(s) to the slave.
 // It is implicitely assumed, that the slave will
 // accepts 8 bytes
 
 if (!TWIM_Start (SlaveAddress, TWIM_WRITE))
 {
 TWIM_Stop ();
 printf ("Could not start TWI Bus for WRITE\n");
 }
 else
 {
 for (i=0;i<8;i++)
 {
 TWIM_Write (j++);
 printf ("Byte %d sent\n", j);
 }
 TWIM_Stop ();
 Delay_ms (1000);
 }
 
 // Do something else
 i++;
 }
 
	return 0;
	}
 
 ********************************************************/
#include <stdio.h>
#include <avr/interrupt.h>

#include "General.h"
#include "TWI_Master.h"

/****************************************************************************
 TWI State codes
 ****************************************************************************/
// General TWI Master staus codes
#define TWI_START					0x08  // START has been transmitted
#define TWI_REP_START				0x10  // Repeated START has been transmitted
#define TWI_ARB_LOST				0x38  // Arbitration lost

// TWI Master Transmitter staus codes
#define TWI_MTX_ADR_ACK				0x18  // SLA+W has been tramsmitted and ACK received
#define TWI_MTX_ADR_NACK			0x20  // SLA+W has been tramsmitted and NACK received
#define TWI_MTX_DATA_ACK			0x28  // Data byte has been tramsmitted and ACK received
#define TWI_MTX_DATA_NACK			0x30  // Data byte has been tramsmitted and NACK received

// TWI Master Receiver staus codes
#define TWI_MRX_ADR_ACK				0x40  // SLA+R has been tramsmitted and ACK received
#define TWI_MRX_ADR_NACK			0x48  // SLA+R has been tramsmitted and NACK received
#define TWI_MRX_DATA_ACK			0x50  // Data byte has been received and ACK tramsmitted
#define TWI_MRX_DATA_NACK			0x58  // Data byte has been received and NACK tramsmitted

// TWI Slave Transmitter staus codes
#define TWI_STX_ADR_ACK				0xA8  // Own SLA+R has been received; ACK has been returned
#define TWI_STX_ADR_ACK_M_ARB_LOST	0xB0  // Arbitration lost in SLA+R/W as Master; own SLA+R has been received; ACK has been returned
#define TWI_STX_DATA_ACK			0xB8  // Data byte in TWDR has been transmitted; ACK has been received
#define TWI_STX_DATA_NACK			0xC0  // Data byte in TWDR has been transmitted; NOT ACK has been received
#define TWI_STX_DATA_ACK_LAST_BYTE	0xC8  // Last data byte in TWDR has been transmitted (TWEA = “0”); ACK has been received

// TWI Slave Receiver staus codes
#define TWI_SRX_ADR_ACK				0x60  // Own SLA+W has been received ACK has been returned
#define TWI_SRX_ADR_ACK_M_ARB_LOST	0x68  // Arbitration lost in SLA+R/W as Master; own SLA+W has been received; ACK has been returned
#define TWI_SRX_GEN_ACK				0x70  // General call address has been received; ACK has been returned
#define TWI_SRX_GEN_ACK_M_ARB_LOST	0x78  // Arbitration lost in SLA+R/W as Master; General call address has been received; ACK has been returned
#define TWI_SRX_ADR_DATA_ACK		0x80  // Previously addressed with own SLA+W; data has been received; ACK has been returned
#define TWI_SRX_ADR_DATA_NACK		0x88  // Previously addressed with own SLA+W; data has been received; NOT ACK has been returned
#define TWI_SRX_GEN_DATA_ACK		0x90  // Previously addressed with general call; data has been received; ACK has been returned
#define TWI_SRX_GEN_DATA_NACK		0x98  // Previously addressed with general call; data has been received; NOT ACK has been returned
#define TWI_SRX_STOP_RESTART		0xA0  // A STOP condition or repeated START condition has been received while still addressed as Slave

// TWI Miscellaneous status codes
#define TWI_NO_STATE				0xF8  // No relevant state information available; TWINT = “0”
#define TWI_BUS_ERROR				0x00  // Bus error due to an illegal START or STOP condition

/*******************************************************
 Public Function: TWIM_Init
 
 Purpose: Initialise the TWI Master Interface
 
 Input Parameter:
 - uint16_t	TWI_Bitrate (Hz)
 
 Return Value: uint8_t
 - FALSE:	Bitrate too high
 - TRUE:		Bitrate OK
 
 *******************************************************/
uint8_t TWIM_Init (uint32_t TWI_Bitrate)
{
    /*
     ** Set TWI bitrate
     ** If bitrate is too high, then error return
     */
    TWBR = ((F_CPU/TWI_Bitrate)-16)/2;
    if (TWBR < 11) return FALSE;
    
    return TRUE;
}
/*******************************************************
 Public Function: TWIM_Start
 
 Purpose: Start the TWI Master Interface
 
 Input Parameter:
 - uint8_t	Device address
 - uint8_t	Type of required Operation:
 TWIM_READ: Read data from the slave
 TWIM_WRITE: Write data to the slave
 
 Return Value: uint8_t
 - TRUE:		OK, TWI Master accessible
 - FALSE:	Error in starting TWI Master
 
 *******************************************************/
uint8_t TWIM_Start (uint8_t Address, uint8_t TWIM_Type)
{
    uint8_t		twst;
    /*
     ** Send START condition
     */
    TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);
    /*
     ** Wait until transmission completed
     */
    while (!(TWCR & (1<<TWINT)));
    /*
     ** Check value of TWI Status Register. Mask prescaler bits.
     */
    twst = TWSR & 0xF8;
    if ((twst != TWI_START) && (twst != TWI_REP_START)) return FALSE;
    /*
     ** Send device address
     */
    TWDR = (Address<<1) + TWIM_Type;
    TWCR = (1<<TWINT)|(1<<TWEN);
    /*
     ** Wait until transmission completed and ACK/NACK has been received
     */
    while (!(TWCR & (1<<TWINT)));
    /*
     ** Check value of TWI Status Register. Mask prescaler bits.
     */
    twst = TWSR & 0xF8;
    if ((twst != TWI_MTX_ADR_ACK) && (twst != TWI_MRX_ADR_ACK)) return FALSE;
    
    return TRUE;
}
/*******************************************************
 Public Function: TWIM_Stop
 
 Purpose: Stop the TWI Master
 
 Input Parameter: None
 
 Return Value: None
 
 *******************************************************/
void TWIM_Stop (void)
{
    /*
     ** Send stop condition
     */
    TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);
    /*
     ** Wait until stop condition is executed and bus released
     */
    while (TWCR & (1<<TWINT));
}
/*******************************************************
 Public Function: TWIM_Write
 
 Purpose: Write a byte to the slave
 
 Input Parameter:
 - uint8_t	Byte to be sent
 
 Return Value: uint8_t
 - TRUE:		OK, Byte sent
 - FALSE:	Error in byte transmission
 
 *******************************************************/
uint8_t TWIM_Write (uint8_t byte)
{
    uint8_t   twst;
    /*
     ** Send data to the previously addressed device
     */
    TWDR = byte;
    TWCR = (1<<TWINT)|(1<<TWEN);
    /*
     ** Wait until transmission completed
     */
    while (!(TWCR & (1<<TWINT)));
    /*
     ** Check value of TWI Status Register. Mask prescaler bits
     */
    twst = TWSR & 0xF8;
    if (twst != TWI_MTX_DATA_ACK) return 1;
    
    return 0;
}
/*******************************************************
 Public Function: TWIM_ReadAck
 
 Purpose: Read a byte from the slave and request next byte
 
 Input Parameter: None
 
 Return Value: uint8_t
 - uint8_t	Read byte
 
 *******************************************************/
uint8_t TWIM_ReadAck (void)
{
    TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWEA);
    while (!(TWCR & (1<<TWINT)));
    
    return TWDR;
}
/*******************************************************
 Public Function: TWIM_ReadAck
 
 Purpose: Read the last byte from the slave
 
 Input Parameter: None
 
 Return Value: uint8_t
 - uint8_t	Read byte
 
 *******************************************************/
uint8_t TWIM_ReadNack (void)
{
    TWCR = (1<<TWINT)|(1<<TWEN);
    while(!(TWCR & (1<<TWINT)));
    
    return TWDR;
}