twi.c

avr单片机的twi（i2c）驱动程序

#define TWI_C
#include "includes.h"

static uchar TWI_buf[TWI_BUFFER_SIZE];
static uchar TWI_msgSize;
static uchar TWI_state = TWI_NO_STATE;
static uchar TWI_statusReg;// = 0;

/*******************************************************
初始化TWI为I2C主机，并处于初始待机状态。注意，初始化完成后，
应在主程序中开放全局中断
********************************************************/
void TWI_Master_Initialise(void)
{
	TWBR = TWI_TWBR;
	TWCR = (1<<TWEN)|(0<<TWIE)|(0<<TWINT)|
		(0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|
		(0<<TWWC);
}
/*******************************************************
Call this function to test if the TWI_ISR is busy transmitting
********************************************************/
char TWI_Transceiver_Busy(void)
{
	return (TWCR &(1<<TWIE));
}
/*******************************************************
Call this function to fetch the state information of the previous
operation.
********************************************************/
char TWI_Get_State_Info(void)//发送数据包
{
	while(TWI_Transceiver_Busy());
	return(TWI_state);
}
/*******************************************************
Call this function to send a prepared message.
********************************************************/
void TWI_Start_Transceiver_With_Data(uchar *msg,uchar msgSize)//检验数据包是否发送完成
{
	uchar temp;
	while(TWI_Transceiver_Busy());
	TWI_msgSize = msgSize;
	TWI_buf[0] = msg[0];
	if(!(msg[0] & (TRUE<<TWI_READ_BIT)))
	{
		for(temp = 1;temp < msgSize; temp++)
			TWI_buf[temp] = msg[temp];
	}
	TWI_statusReg = FALSE;
	TWI_state = TWI_NO_STATE;
	TWCR = (1<<TWEN)|
		(1<<TWIE)|(1<<TWINT)|
		(0<<TWEA)|(1<<TWSTA)|(0<<TWSTO)|
		(0<<TWWC);
}
/*******************************************************
Call this function to resend the last message.
********************************************************/
void TWI_Start_Transceiver(void)
{
	while(TWI_Transceiver_Busy());
	TWI_statusReg = FALSE;
	TWI_state = TWI_NO_STATE;
	TWCR = (1<<TWEN)|
		(1<<TWIE)|(1<<TWINT)|
		(0<<TWEA)|(1<<TWSTA)|(0<<TWSTO)|
		(0<<TWWC);
}
/*******************************************************
Call this function to read out hte requested data from the
TWI transceiver buffer.
********************************************************/
uchar TWI_Get_Data_From_Transceiver(uchar *msg,uchar msgSize)
{
	uchar i;
	while(TWI_Transceiver_Busy());
	if(TWI_statusReg)
	{
		for(i = 0;i < msgSize; i++)
		{
			msg[i] = TWI_buf[i];
		}
	}
	return(TWI_statusReg);
}

//************************TWI 中断服务程序**************************//

#pragma interrupt_handler twi:34
void twi(void)
{
	static uchar TWI_bufPtr;
	switch(TWSR)
	{
		case TWI_START:
		case TWI_REP_START:
			TWI_bufPtr = 0;
		case TWI_MTX_ADR_ACK:
		case TWI_MTX_DATA_ACK:
			if(TWI_bufPtr < TWI_msgSize)
			{
				TWDR = TWI_buf[TWI_bufPtr++];
				TWCR = (1<<TWEN)|
            		(1<<TWIE)|(1<<TWINT)|
            		(0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|
            		(0<<TWWC);
			}
			else
			{
				TWI_statusReg = TRUE;
            	TWCR = (1<<TWEN)|
            		(0<<TWIE)|(1<<TWINT)|
            		(0<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|
            		(0<<TWWC);
			}
			break;
		case TWI_MRX_DATA_ACK:
			TWI_buf[TWI_bufPtr++] = TWDR;
		case TWI_MRX_ADR_ACK:
			if(TWI_bufPtr < (TWI_msgSize-1))
			{
				TWCR = (1<<TWEN)|
            		(1<<TWIE)|(1<<TWINT)|
            		(1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|
            		(0<<TWWC);
			}
			else
			{
            	TWCR = (1<<TWEN)|
            		(1<<TWIE)|(1<<TWINT)|
            		(0<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|
            		(0<<TWWC);
			}
			break;
		case TWI_MRX_DATA_NACK:
            TWI_buf[TWI_bufPtr++] = TWDR;
			TWI_statusReg = TRUE;
            TWCR = (1<<TWEN)|
         		(0<<TWIE)|(1<<TWINT)|
         		(0<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|
         		(0<<TWWC);
			break;
		case TWI_ARB_LOST:
            TWCR = (1<<TWEN)|
         		(0<<TWIE)|(1<<TWINT)|
         		(0<<TWEA)|(1<<TWSTA)|(0<<TWSTO)|
         		(0<<TWWC);
			break;			
        case TWI_MTX_ADR_NACK:	
        case TWI_MRX_ADR_NACK:
        case TWI_MTX_DATA_NACK:
		case TWI_BUS_ERROR:
		default:
			TWI_state = TWSR;
            TWCR = (1<<TWEN)|
         		(0<<TWIE)|(0<<TWINT)|
         		(0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|
         		(0<<TWWC);
	}
}