avr SPI transfer function only works once

Question

u8 SPI_transfer(u8 copy_u8Reciever)
{
    SPDR=copy_u8Reciever;
    while (GET_BIT(SPSR,7)==0);
    return SPDR;

I can only use the function once , in the second time it goes on an infinite loop , it is weird because I used this code before and it worked very well , now the code is stuck in this while loop

Answer 1

To check if SPI is working correctly use an oszilloscope or make a loopback if there are some buttons and leds on your board.

Possible configuration issues:

• controller is not in master mode
• SPI Clock is to high
• wrong polarity/phase of SCK and MOSI
• problems with SS
• SCK, MOSI and SS are not configured as output

Loopback (Connect MOSI with MISO):

unsigned char spi_init()
{
    // ...

    // Setup SCK, MOSI and SS as output
    // PORT configuration gets overwritten from SPI controller
    SPI_DDR  |= (1<<SPI_SCK) | (1<<SPI_MISO) | (1<<SPI_MOSI) | (1<<SPI_SS);
    
    // Check if master abort has occurred
    if(!(SPCR & (1<<MSTR)))
        return 0xFF;    // Return master abort
    return 0x00;        // Return no fault
}


unsigned char spi_transfer(unsigned char data)
{
    SPDR = data; 
    while(!(SPSR & (1<<SPIF)));
    
    return SPDR;    // Return received data from the bus
}

int main()
{
   // Define some output if possible
   DDRC = 0xFF;

   spi_init();

   while()
   {
       // Write some input to output
       PORTC = spi_transfer(PINA);
   }
}