AVR的SPI入门

#include <avr/io.h>

#include <avr/interrupt.h>

void SPI0_init(void);

volatile uint8_t receiveData = 0;

volatile uint8_t writeData = 0;

void SPI0_init(void)

{

 PORTA.DIR &= ~PIN4_bm; /* Set MOSI pin direction to input */

 PORTA.DIR |= PIN5_bm; /* Set MISO pin direction to output */

 PORTA.DIR &= ~PIN6_bm; /* Set SCK pin direction to input */

 PORTA.DIR &= ~PIN7_bm; /* Set SS pin direction to input */

 SPI0.CTRLA = SPI_DORD_bm /* LSB is transmitted first */

 | SPI_ENABLE_bm /* Enable module */

 & (~SPI_MASTER_bm); /* SPI module in Slave mode */

 SPI0.INTCTRL = SPI_IE_bm; /* SPI Interrupt enable */

}

ISR(SPI0_INT_vect)

{

 receiveData = SPI0.DATA;

 SPI0.DATA = writeData;

 SPI0.INTFLAGS = SPI_IF_bm; /* Clear the Interrupt flag by writing 1 */

}

int main(void)

{ 

 SPI0_init();

 sei(); /* Enable Global Interrupts */

 while (1)

 {

 ;

 }

}

#include <avr/io.h>

void SPI0_init(void);

void slaveSelect(void);

void slaveDeselect(void);

uint8_t SPI0_exchangeData(uint8_t data);

void SPI0_init(void)

{

 PORTA.DIR |= PIN4_bm; /* Set MOSI pin direction to output */

 PORTA.DIR &= ~PIN5_bm; /* Set MISO pin direction to input */

 PORTA.DIR |= PIN6_bm; /* Set SCK pin direction to output */

 PORTA.DIR |= PIN7_bm; /* Set SS pin direction to output */

 SPI0.CTRLA = SPI_CLK2X_bm /* Enable double-speed */

 | SPI_DORD_bm /* LSB is transmitted first */

 | SPI_ENABLE_bm /* Enable module */

 | SPI_MASTER_bm /* SPI module in Master mode */

 | SPI_PRESC_DIV16_gc; /* System Clock divided by 16 */

 SPI0.CTRLB |= SPI_MODE_3_gc; /* Data Mode 3 */

}

uint8_t SPI0_exchangeData(uint8_t data)

{

 SPI0.DATA = data;

 while (!(SPI0.INTFLAGS & SPI_IF_bm)) /* waits until data is exchanged*/

 {

 ;

 }

 

 return SPI0.DATA;

}

void slaveSelect(void)

{

 PORTA.OUT &= ~PIN7_bm; // Set SS pin value to LOW

}

void slaveDeselect(void)

{

 PORTA.OUT |= PIN7_bm; // Set SS pin value to HIGH

}

int main(void)

{

 uint8_t data = 0;

 SPI0_init();

 while (1)

 {

 slaveSelect(); 

 SPI0_exchangeData(data);

 slaveDeselect();

 }

}