teensy-spi/SPI.cpp

/*
 * Copyright (c) 2010 by Cristian Maglie <c.maglie@bug.st>
 * SPI Master library for arduino.
 *
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of either the GNU General Public License version 2
 * or the GNU Lesser General Public License version 2.1, both as
 * published by the Free Software Foundation.
 */

#include "SPI.h"
#include "pins_arduino.h"

SPIClass SPI;

uint8_t SPIClass::interruptMode = 0;
uint8_t SPIClass::interruptMask = 0;
uint8_t SPIClass::interruptSave = 0;

void SPIClass::begin()
{
	// Set SS to high so a connected chip will be "deselected" by default
	digitalWrite(SS, HIGH);

	// When the SS pin is set as OUTPUT, it can be used as
	// a general purpose output port (it doesn't influence
	// SPI operations).
	pinMode(SS, OUTPUT);

	// Warning: if the SS pin ever becomes a LOW INPUT then SPI
	// automatically switches to Slave, so the data direction of
	// the SS pin MUST be kept as OUTPUT.
	SPCR |= _BV(MSTR);
	SPCR |= _BV(SPE);

	// Set direction register for SCK and MOSI pin.
	// MISO pin automatically overrides to INPUT.
	// By doing this AFTER enabling SPI, we avoid accidentally
	// clocking in a single bit since the lines go directly
	// from "input" to SPI control.	 
	// http://code.google.com/p/arduino/issues/detail?id=888
#ifdef __AVR__
	pinMode(SCK, OUTPUT);
	pinMode(MOSI, OUTPUT);
#endif
}

void SPIClass::end() {
	SPCR &= ~_BV(SPE);
}

void SPIClass::usingInterrupt(uint8_t interruptNumber)
{
	uint8_t mask;

	if (interruptMode > 1) return;

	noInterrupts();
	switch (interruptNumber) {
	#ifdef SPI_INT0_MASK
	case 0: mask = SPI_INT0_MASK; break;
	#endif
	#ifdef SPI_INT1_MASK
	case 1: mask = SPI_INT1_MASK; break;
	#endif
	#ifdef SPI_INT2_MASK
	case 2: mask = SPI_INT2_MASK; break;
	#endif
	#ifdef SPI_INT3_MASK
	case 3: mask = SPI_INT3_MASK; break;
	#endif
	#ifdef SPI_INT4_MASK
	case 4: mask = SPI_INT4_MASK; break;
	#endif
	#ifdef SPI_INT5_MASK
	case 5: mask = SPI_INT5_MASK; break;
	#endif
	#ifdef SPI_INT6_MASK
	case 6: mask = SPI_INT6_MASK; break;
	#endif
	#ifdef SPI_INT7_MASK
	case 7: mask = SPI_INT7_MASK; break;
	#endif
	default:
		interruptMode = 2;
		interrupts();
		return;
	}
	interruptMode = 1;
	interruptMask |= mask;
	interrupts();
}