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- /* sd2snes - SD card based universal cartridge for the SNES
- Copyright (C) 2009-2010 Maximilian Rehkopf <otakon@gmx.net>
- This file was adapted from sd2iec, written by Ingo Korb.
- Original copyright header follows:
- */
- /* sd2iec - SD/MMC to Commodore serial bus interface/controller
- Copyright (C) 2007-2009 Ingo Korb <ingo@akana.de>
- Inspiration and low-level SD/MMC access based on code from MMC2IEC
- by Lars Pontoppidan et al., see sdcard.c|h and config.h.
- FAT filesystem access based on code from ChaN and Jim Brain, see ff.c|h.
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; version 2 of the License only.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
- spi.c: Low level SPI access
- Extended, optimized and cleaned version of code from MMC2IEC,
- original copyright header follows:
- //
- // Title : SPI module
- // Author : Lars Pontoppidan
- // Date : January, 2007
- // Version : 1.03
- // Target MCU : Atmel AVR Series
- //
- // DESCRIPTION:
- // This module implements initialization, sending and receiving bytes using
- // hardware SPI on an AVR.
- //
- // DISCLAIMER:
- // The author is in no way responsible for any problems or damage caused by
- // using this code. Use at your own risk.
- //
- // LICENSE:
- // This code is distributed under the GNU Public License
- // which can be found at http://www.gnu.org/licenses/gpl.txt
- //
- */
- // FIXME: Integrate into sdcard.c
- #include <avr/io.h>
- #include "avrcompat.h"
- #include "spi.h"
- // access routines
- void spiInit(void)
- {
- volatile uint8_t dummy;
- // setup SPI I/O pins
- SPI_PORT = (SPI_PORT & ~SPI_MASK) | SPI_SCK | SPI_SS | SPI_MISO;
- SPI_DDR = (SPI_DDR & ~SPI_MASK) | SPI_SCK | SPI_SS | SPI_MOSI;
- // setup SPI interface:
- // interrupts disabled, SPI enabled, MSB first, master mode,
- // leading edge rising, sample on leading edge, clock = f/4
- SPCR = 0b01010000;
- // Enable SPI double speed mode -> clock = f/2
- SPSR = _BV(SPI2X);
- // clear status
- dummy = SPSR;
- // clear receive buffer
- dummy = SPDR;
- }
- inline uint8_t spiTransferByte(uint8_t data)
- {
- // send the given data
- SPDR = data;
- // wait for transfer to complete
- loop_until_bit_is_set(SPSR, SPIF);
- // *** reading of the SPSR and SPDR are crucial
- // *** to the clearing of the SPIF flag
- // *** in non-interrupt mode
- // return the received data
- return SPDR;
- }
- inline uint32_t spiTransferLong(const uint32_t data)
- {
- // It seems to be necessary to use the union in order to get efficient
- // assembler code.
- // Beware, endian unsafe union
- union {
- uint32_t l;
- uint8_t c[4];
- } long2char;
- long2char.l = data;
- // send the given data
- SPDR = long2char.c[3];
- // wait for transfer to complete
- loop_until_bit_is_set(SPSR, SPIF);
- long2char.c[3] = SPDR;
- SPDR = long2char.c[2];
- // wait for transfer to complete
- loop_until_bit_is_set(SPSR, SPIF);
- long2char.c[2] = SPDR;
- SPDR = long2char.c[1];
- // wait for transfer to complete
- loop_until_bit_is_set(SPSR, SPIF);
- long2char.c[1] = SPDR;
- SPDR = long2char.c[0];
- // wait for transfer to complete
- loop_until_bit_is_set(SPSR, SPIF);
- long2char.c[0] = SPDR;
- return long2char.l;
- }
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