AVR SPI通讯例程（中断方式）

// SPI Receiver buffer
#define SPI_RX_BUFFER_SIZE 64
char spi_rx_buffer[SPI_RX_BUFFER_SIZE];

#if SPI_RX_BUFFER_SIZE<256
unsigned char spi_rx_wr_index,spi_rx_rd_index,spi_rx_counter;
#else
unsigned int spi_rx_wr_index,spi_rx_rd_index,spi_rx_counter;
#endif

// This flag is set on SPI Receiver buffer overflow
bit spi_rx_buffer_overflow;

// SPI Transmitter buffer
#define SPI_TX_BUFFER_SIZE 64
char spi_tx_buffer[SPI_TX_BUFFER_SIZE];

#if SPI_TX_BUFFER_SIZE<256
unsigned char spi_tx_wr_index, spi_tx_rd_index, spi_tx_counter;
#else
unsigned int spi_tx_wr_index, spi_tx_rd_index, spi_tx_counter;
#endif

unsigned char spi_counter = 0;

#ifdef _MASTER_
#define SS PORTB.4
#endif

// SPI interrupt service routine