spi "freezes"

Development Boards MicroMod
1

Hello,

I have an issue with spi that freezes. I’m using atmega88 with nrf24l01 but when i try to test spi communication i get stuck.

I initialize spi based on atmel specifications:

DDRB |= (1<<DDB5) | (1<<DDB3) | (1<<DDB2) |(1<<DDB1);
SPCR |= (1<<SPE)|(1<<MSTR);

And when I try to test out writing to spi (and print out to terminal ) i get stuck looping… ( i have usart initialized and used without any problems)

char spi_rw(unsigned char x)
{
    SPDR = x;   
    //get stuck in this while loop
    while(!(SPSR & (1<<SPIF)));
    //printing to terminal after get's out of loop but never go out   
    return SPDR;
}

I’m trying to read STATUS register:

uint8_t get_reg(uint8_t reg)
{   

    _delay_us(10);
    CLEARBIT(PORTB, 2);    //CSN low so nrf start listen for command
    _delay_us(10);
    spi_rw(R_REGISTER + reg);   
    _delay_us(10);
    reg = spi_rw(NOP);
    _delay_us(10);
    SETBIT(PORTB, 2);    //CSN IR_High nrf do nothing now
    return reg;   
}

I try calling get_reg(STATUS) and passing it to usart to print out resultand I get nowhere since code stuck in while loop.

P.S. i use this simple functions to set and clear bits

#define BIT(x) (1<<(x))
#define SETBITS(x,y) ((x)|=(y)))
#define CLEARBITS(x,y) ((x) &=(~(y)))
#define SETBIT(x,y) SETBITS((x), (BIT((y))))
#define CLEARBIT(x,y) CLEARBITS((x), (BIT((Y))))

Thanks in advance, any help would be greatly appreciated. (sorry if i create thread on wrong place)

2

This may not explain your particular problem, but the SPI will freeze if you forget to set SS (PORTB2) to high before initializing the SPI hardware, as SS low will make the controller switch to slave mode.

3

Thanks,

that was a problem which i overlooked… I had badly organized project (and to tired and frustrated) with huge amount of code and added some other initialization that put B2 to low :frowning: … i fixed it before post was approved but thank you very much :slight_smile: