Why can't I read data from the SPI slave device?

[sunsy]

Posted on May 29, 2007 at 14:08

Why can't I read data from the SPI slave device?

[sunsy]

Posted on May 17, 2011 at 12:08

I used upsd3354D with TC72(Microchip) , the SPITXD and SPICLK works well. But, I can't READ any byte from the slave device, the SPIRXD keeps high all the time.

e.g. Read the TC72 ID (0x54), but I read 0xFF.

unsigned char ReadTemperID(void)

{ unsigned char t_id;

P1_7=1;

while (SPISTAT & SPI_BUSY_FLAG); //Waiting if SPI is busy

SPICON0|=RE;

while (!(SPISTAT & SPI_TI_FLAG)); //Waiting if SPI transfer is full

SPITDR=0x00; //Send 0x02 to select temper MSB byte

while (!(SPISTAT & SPI_TRANSMIT_END_FLAG));

while (!(SPISTAT & SPI_RI_FLAG));

SPITDR=SPI_Dummy; //Provide read clock by sending a dummy byte

while (!(SPISTAT & SPI_TRANSMIT_END_FLAG)); //Waiting if SPI transfer is full

while (!(SPISTAT & SPI_RI_FLAG)); //Waiting if SPI receiver is empty

t_id=SPIRDR; //Read data from SPIRDR register

SPICON0&=(~RE); //Disable SPI receiver

P1_7=0;

return(t_id); //Return data received

}

[danes]

Posted on May 17, 2011 at 12:08

I actually have the same problem with the 24LC640. Even when I attempt to read the internal registry I get 0xFF.