Colony

/**

 * @file spi.c

 * @brief Basic SPI module to handle encoders

 * @author Colony Project, CMU Robotics Club

 * @bug Not tested

 *        Need to move spi.h include into dragonfly_lib.h when stable

 **/

#include <avr/interrupt.h>

#include <dragonfly_lib.h>

#include "spi.h"

static volatile char spi_bytes; /* number of bytes to read */

static spi_fun_recv_t spi_recv_func; /* byte handler */

void spi_init (spi_fun_recv_t recv_func)

{

    /*  Enable Interrupt, Enable SPI Module, MSB First, Master Mode, Clock div = 64 */

    SPCR = _BV(SPE) | _BV(SPIE) | _BV(DORD) | _BV(MSTR) | _BV(SPR1) | _BV(SPR0);

    SPSR = _BV(SPI2X); 

    /* Set SCLK, SS, MOSI as outputs. MISO as input */

    DDRB = MOSI | SCLK | SS;

    DDRB &= ~MISO;

    /* Keep SS high until transmit */

    PORTB |= SS;

    /* set function to be executed when we receive a byte */

    spi_recv_func = recv_func;

    spi_bytes = 0;

}

/* Transfer a given byte to slave and receive a byte */

void spi_transfer(char bytes)

{

    spi_bytes = bytes;

    PORTB &= ~SS; /* Set SS low to initiate transmission */

    SPDR = 0xff; /* Initiate data transmision */

}

ISR(SIG_SPI) 

{

    /* only handle intterupt when we are expecting data */

    if(spi_bytes > 0){

        /* process byte */

        spi_recv_func(SPDR);

        /* if we've read all the bytes, set SS high to end transmission,

         * otherwise get the next byte  */

        if(--spi_bytes == 0)

            PORTB |= SS;

        else 

            SPDR = 0xff;

    }

}