ATmega88 @ 8MHz SPI-Kommunikation mit Flash-Speicher SST25VF016B und Auslesen des Statusregisters

spi-flash-01.c

/* spi_flash_01.c
* SPI-Kommunikation mit Flash-Speicher SST25VF016B und Auslesen des Statusregisters
* Controller: ATmega88 @ 8MHz
*/
#include <avr/io.h>
#define WP      (1<<PC5)      // Write Protect disable @ PC5
#define HOLD    (1<<PC4)      // Stop serial communication disable @ PC4
#define CE      (1<<PB2)      // Chip Enable @ PB2
#define MOSI    (1<<PB3)      // Master Out Slave In @ PB3
#define MISO    (1<<PB4)      // Master In Slave Out @ PB4
#define SCK     (1<<PB5)      // Clock @ PB5
 
uint8_t status_register=0;
 
void SPI_MasterInit(void)                   // Init SPI Master
{
    DDRB = MOSI|SCK|CE;                     // Set MOSI, SCK, CE output
    SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1);  // Enable SPI, Master, set clock rate fck/64
}
 
void SPI_MasterTransmit(uint8_t data)       // Transmit SPI data
{
    SPDR = data;                            // Start transmission
    while(!(SPSR & (1<<SPIF)));               // Wait for transmission complete
}
 
uint8_t SPI_SlaveReceive(void)              // Receive SPI data
{
    while(!(SPSR & (1<<SPIF)));               // Wait for reception complete
    return SPDR;                            // Return SPI-Dataregister
}
 
int main(void)
{
    DDRC |= WP | HOLD;      // Set WP, HOLD output
    PORTC |= WP|HOLD;       // Set WP, HOLD high
     
    SPI_MasterInit();       // Init SPI Master
     
    PORTB &= ~CE;           // CE = low (start communication)
     
    SPI_MasterTransmit(0x05);   // Send command 0x05 (Read the status register)
    SPI_MasterTransmit(0x00);   // Send one dummy byte
     
    status_register = SPI_SlaveReceive();   // Read received SPI data and store in status_register
     
    PORTB |= CE;                            // CE = high (end of communication)
    status_register=0;                      // set the variable status_register to 0
     
    while(1)
    {
        asm("NOP");     // NOP = no operation (Inline Assembler Instruction)
    }
}