I2C Master Slave Read data from slave

[SneaKSz]

Hello all

I'm experiencing problems with receiving data from my slave. The slave knows its addressed and sets its data into SSPBUF. The data also clocks out, but when I read the SSPBUF in the master, it's not the value I send over I2C.

This is the picture of the master receiving data ( address = 0x08, the +1 for reading, data = 0xAA).

**broken link removed**

https://img191.imageshack.us/i/masterreadslave0xaa.png/

This is the routine :

					SendStart(); // send S
					Delay10TCY();// 	
					SendByte2(0x08+1); // Address READ
					Delay10TCYx(10);// 	
					SSPCON2bits.RCEN=1;
					Delay10TCYx(10);// 	
					SSPFlag();
					Delay10TCY();
			//		test=ReadI2C();
					while(SSPSTATbits.BF == 0);
					Delay10TCY();
					Nack();
					Delay10TCY();
					SendStop();
					Delay10TCY();
					Delay10TCY();
					SSPCON2bits.RCEN=0;
				//	Delay10KTCYx(1);// 
					Delay10TCY();
					errorV= SSPBUF;// put the SSPBUF in a char

void SendStart(){
SSPCON2bits.SEN=1;
SSPFlag();
}

void SendStop(){
SSPCON2bits.PEN=1; // P activeren
SSPFlag();
}
void Nack(){
SSPCON2bits.ACKEN=1;
SSPCON2bits.ACKDT=1;	
}
void SSPFlag() {
while(PIR1bits.SSPIF==0); // wait until sent
PIR1bits.SSPIF=0; // set low
}

The problem is that I can't send a NACK and a STOP bit. Someone sees the wrong sequence in my code?

 

[SneaKSz]

Fixed : The problem was there is a busbuffer and opto coupler between the master & slave. A resistor was chosen badly and the LOW level was 4.5V, by choosing a correct resistor, the low level went to 0.5V and the master received a NACK.

Thanks