cpu/avr/spi.c

   1 /*
   2  * Copyright (c) 2007, Swedish Institute of Computer Science
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the Institute nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)$Id: spi.c,v 1.1 2007/01/25 18:22:55 bg- Exp $
  30  */
  31
  32 #include <avr/io.h>
  33
  34 #include "contiki-conf.h"
  35
  36 /*
  37  * On the Tmote sky access to I2C/SPI/UART0 must always be
  38  * exclusive. Set spi_busy so that interrupt handlers can check if
  39  * they are allowed to use the bus or not. Only the CC2420 radio needs
  40  * this in practice.
  41  *
  42  */
  43 unsigned char spi_busy = 0;
  44
  45 /*
  46  * Initialize SPI bus.
  47  */
  48 void
  49 spi_init(void)
  50 {
  51   static unsigned char spi_inited = 0;
  52
  53   if (spi_inited)
  54     return;
  55
  56   /* Initalize ports for communication with SPI units. */
  57   /* CSN=SS and must be output when master! */
  58   DDRB  |= BV(MOSI) | BV(SCK) | BV(CSN);
  59   PORTB |= BV(MOSI) | BV(SCK);
  60
  61   /* Enables SPI, selects "master", clock rate FCK / 2, and SPI mode 0 */
  62   SPCR = BV(SPE) | BV(MSTR);
  63   SPSR = BV(SPI2X);
  64 }