upsd3300_i2c.c

一个介绍upsd33系列单片机I2C编程的好例子

		i2c_state=I2C_TIME_OUT;
		return (i2c_state);
	}									// I2C master receive timeout
	else {
		return(i2c_state); 
	}									// Return I2C current state
}

/*-------------------------------------------------------------------------
upsd_i2c_slave_Xmit(Data_Ptr, N_Ptr)

This function is used to transmit data to master, only for slave.

Data_Ptr	- unsigned char*
			- address pointer of transmit buffer
N_Ptr		- unsigned char*
			- the length of data buffer transmitted to master.
 
Returns:
I2C_SX_END		6			//Slave Mode - transmission is complete
I2C_TIME_OUT	9			//I2C Timed Out
I2C_NACK		13			//I2C NACK (No Acknowledge)
I2C_BUSLOST		14			//I2C bus lost
-------------------------------------------------------------------------*/
unsigned char upsd_i2c_slave_Xmit(unsigned char* Data_Ptr,
									unsigned char* N_Ptr)
{
	EA=0;
	i2c_xmit_buf=Data_Ptr; 						// Initialize pointer to transmit buffer
	i2c_master = 0;
	i2c_xmitr = 1;								// Set up for Slave transmitter
	S1CON &= ~STO;								// Disable STOP control bit
	i2c_data_index=0;
	S1DAT = i2c_xmit_buf[i2c_data_index];  		// Send first data to master
	i2c_data_index++;
	i2c_state=I2C_SX; 							// Set I2C current status
	EA=1;
	if(upsd_i2c_Timeout(I2C_SX,10000)==1){
		S1CON&=~ENI;i2c_slave_addressed=0;i2c_state=I2C_TIME_OUT;return(i2c_state);
	}	   										// I2C slave timeout return
	else {
		*N_Ptr=i2c_data_index;return(i2c_state);
	}			    							// return current I2C state and the length
												// of the data buffer transmitted to master
}
/*-------------------------------------------------------------------------
upsd_i2c_slave_Recv(Data_Ptr, N_Ptr)

This function is used to receive data from a master while in slave mode.

Data_Ptr	- unsigned char*
			- address pointer to receive buffer
N_Ptr		- unsigned char*
			- the length of received data from the master.
 
Returns:
I2C_TIME_OUT	9			//I2C Timed Out
I2C_SR_END		11			//Slave Mode - reception complete
I2C_NACK		13			//I2C NACK (No Acknowledge)
I2C_BUSLOST		14			//I2C bus lost
I2C_SX_APP		15			//Slave to transmit data to master
-------------------------------------------------------------------------*/
unsigned char upsd_i2c_slave_Recv(unsigned char* Data_Ptr,
									unsigned char* N_Ptr)
{
	EA=0;
	S1CON&=~ENI;
	i2c_rcv_buf=Data_Ptr;						// initialize pointer to receive buffer
	i2c_master = 0;  
	i2c_xmitr = 0;								// Set to Slave transmitter
	i2c_data_index=0;
	i2c_state=I2C_SR;	 						// Set I2C current status to Slave Read
	S1CON|=ENI;
	EA=1;
	if(upsd_i2c_Timeout(I2C_SR,10000)==1){
		S1CON&=~ENI;i2c_slave_addressed=0;i2c_state=I2C_TIME_OUT; return(i2c_state); 
	}	    									// Slave receive timeout
	else {
		*N_Ptr=i2c_data_index; return(i2c_state);
	}											// Return I2C current state
}

/*------------------------------------------------------------------------	 
I2C Interrupt Service Routine

There are several types of interrupts handled by the ISR.

1. The address packet has been transmitted by master or received by slave with AA=1.
2. The data has been transmitted or received by master.
3. The data has been transmitted or recieved by addressed slave with AA=1.
4. The STOP condition has been received by addressed slave with AA=1.

------------------------------------------------------------------------*/ 

void i2c_isr (void) interrupt I2C_VECTOR using 2 {	
	i2c_sta=S1STA;												// Store S1STA register
	S1STA&=~INTR;											    // Clear INTR flag
	toggle=0;

	//------Master transmit operation--------------------------------------------
	if (i2c_master & i2c_xmitr){							// master transmitter mode
		if ((i2c_sta & BLOST) !=0){ 						// if bus lost, read dummybyte to turn to Slave mode
			dummybyte=S1DAT;
			i2c_state=I2C_BUSLOST;							// Indicate the bus was lost
		}	
		else if ((i2c_sta & _ACKREP) !=0){
			S1CON |=STO;
			S1DAT=dummy; 									// if no ACK, send STOP condition to Bus
			i2c_state=I2C_NACK;								// Indicate NACK (no ACK)
		}
		else
		{	
			if((i2c_data_index)<=(i2c_data_len-1))
			{
				S1DAT = i2c_xmit_buf[i2c_data_index];	 	//send data from Master
				i2c_data_index++;  							//increment data-pointer
			}
			else if(i2c_data_index==i2c_data_len)
			{   
				S1CON |= STO;								// set STO (stop bit) for last data byte to be sent
				S1DAT=dummy;
				i2c_state=I2C_MX_END;						// Indicate the Master transmission is complete
			}
		}
	}

	//------Master receive operation--------------------------------------------
	if (i2c_master & ~i2c_xmitr){							// master receive mode
		//Handle interrupt in address field
		if(((S1CON&AA)==0)& (i2c_data_index==0))
		{
			if ((i2c_sta & _ACKREP) !=0){
				S1CON |=STO;
				dummybyte=S1DAT; 							
				i2c_state=I2C_NACK;							// indicate NACK (no ACK)
				return;  									
			}
			else
			{
				dummybyte=S1DAT;	 						//dummy read 
				if(i2c_data_len!=1)S1CON |= AA;   			//enable ACK to prepare to receive data from slave
				i2c_data_index++;
				return;
			}
		} 

		//Handle reception of data
		else
		{
			if(i2c_data_index<i2c_data_len)
			{
	
				i2c_rcv_buf[i2c_data_index-1] = S1DAT;	   		// Receive data
				i2c_data_index++;						  		// Increment data-pointer
				if(i2c_data_index==i2c_data_len){S1CON&=~AA;} 	// Disable ACK to return a NACK when
																//	 master received the last byte of data.
			}
			else  				
			{   
				S1CON |=STO;								// Generate a STOP condition on Bus
				i2c_rcv_buf[i2c_data_index-1] = S1DAT;		// Receive the last byte of data
				i2c_state=I2C_MR_END;						// Indicate Master reception is complete
			}
		}
	}

	//------slave operation--------------------------------------------
	if(i2c_master==0){
		//Handle STOP interrupt
		if((i2c_sta&STOP)!=0){
			if(i2c_slave_addressed==1){
				if(i2c_xmitr==1){
					i2c_state=I2C_SX_END;						// Indicate slave transmission is complete
					i2c_slave_addressed=0;					    // Reset addressed flag
					S1CON&=~ENI;								// Disable I2C to isolate slave from bus
					return;
				}
				else
				{
					i2c_rcv_buf[i2c_data_index] = S1DAT;		// Get last byte of data from Master
					i2c_slave_addressed=0;					    // Reset addressed flag
					i2c_state=I2C_SR_END;						// Indicate the data has been received completely
					S1CON&=~ENI;								// Disable I2C to isolate slave from bus
					return;
				}
			}
		}
		//Handle Address field interrupt
		else if(((S1CON&ADDR)!=0)&((S1CON&AA)!=0)){
			S1CON&=~ADDR;										// Clear ADDR flag
			i2c_slave_addressed=1;						    	// Set addressed flag bit													// if received address information, identify read or write command
			if((i2c_sta&TX_MODE)!=0){
				i2c_state=I2C_SX_APP;							// Indicate slave is required to transmit data to master
				return;
			}
			else{
				dummybyte=S1DAT;								// Dummy read
				return;
			}
		}
		//Handle data field interrupt
		else if(i2c_slave_addressed==1)
		{
			if(i2c_xmitr==0)
			{   
				
				i2c_rcv_buf[i2c_data_index] = S1DAT;			// Get data byte from Master
				i2c_data_index++;								// Increment data-pointer
			}
			else
			{
				if((i2c_sta &_ACKREP)!=0)
				{	
					S1DAT=dummy; 								// Dummy write
				}
				else
				{
					S1DAT = i2c_xmit_buf[i2c_data_index];		// Send data
					i2c_data_index++;							// Increment data-pointer
				}
			}
		}
	}
}