contiki/cpu/avr/spi.c

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/*
* Copyright (c) 2007, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)$Id: spi.c,v 1.1 2007/01/25 18:22:55 bg- Exp $
*/
#include <avr/io.h>
#include "contiki-conf.h"
/*
* On the Tmote sky access to I2C/SPI/UART0 must always be
* exclusive. Set spi_busy so that interrupt handlers can check if
* they are allowed to use the bus or not. Only the CC2420 radio needs
* this in practice.
*
*/
unsigned char spi_busy = 0;
/*
* Initialize SPI bus.
*/
void
spi_init(void)
{
static unsigned char spi_inited = 0;
if (spi_inited)
return;
/* Initalize ports for communication with SPI units. */
/* CSN=SS and must be output when master! */
DDRB |= BV(MOSI) | BV(SCK) | BV(CSN);
PORTB |= BV(MOSI) | BV(SCK);
/* Enables SPI, selects "master", clock rate FCK / 2, and SPI mode 0 */
SPCR = BV(SPE) | BV(MSTR);
SPSR = BV(SPI2X);
}