Colony

/**

 * @file spi.c

 * @brief Basic SPI module to handle encoders

 * @author Colony Project, CMU Robotics Club

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

 **/

#include <avr/interrupt.h>

#include "spi.h"

unsigned char spi_initd=0;

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

static spi_fun_recv_t spi_recv_func; /* byte handler */

static spi_fun_recv_complete_t spi_recv_complete_func; /*transmission completion handler */

/** 

* @brief Initialize SPI hardware for communication.

* 

* @param recv_func The function to be called for each byte of data received.

* @param recv_complete_func  The function to be called at the end of a complete transmission.

*

* @return 0 if init succesfull, an error code otherwise

*/

int spi_init (spi_fun_recv_t recv_func, spi_fun_recv_complete_t recv_complete_func)

{

    if(spi_initd) {

      return ERROR_INIT_ALREADY_INITD;

    }

    /*  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_recv_complete_func = recv_complete_func;

    spi_bytes = 0;

    //usb_puts("\tspi.c Debug: SPI INITIALIZED\n");

    spi_initd=1;

    return 0;

}

/** 

* @brief Transfer a given byte to slave and receive a byte 

* 

* @param bytes The number of bytes to be transferred.

**/

int spi_transfer(char bytes)

{

    if(!spi_initd)

      return ERROR_LIBRARY_NOT_INITD;

    spi_bytes = bytes;

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

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

    return 0;

}

ISR(SIG_SPI) 

{

        //usb_puts("Interrupt");

    /* 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){

                //usb_puts("Read all bytes\r\n");

                PORTB |= SS;

                if(spi_recv_complete_func)

                        spi_recv_complete_func();

        }else {

                //usb_puts("There are this many bytes left: "); usb_puti(spi_bytes);usb_puts("\r\n");

                SPDR = 0xff;

        }

    }

}