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123 lines
1.7 KiB
C
123 lines
1.7 KiB
C
/*
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* fw/mmc-hw.c - MMC hardware interface
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*
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* Written 2012 by Werner Almesberger
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* Copyright 2012 Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <stdint.h>
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#ifdef AVR
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#include "io.h"
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#else /* AVR */
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#include "ben-io.h"
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#endif /* !AVR */
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#include "delay.h"
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#include "mmc-hw.h"
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/*
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* Pin assignment from
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* http://alumni.cs.ucr.edu/~amitra/sdcard/ProdManualSDCardv1.9.pdf
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*
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* Pin SD mode SPI mode
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* 1 DAT3 Chip Select (active low)
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* 2 CMD MOSI
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* 3 VSS VSS
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* 4 VDD VDD
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* 5 CLK Clock
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* 6 VSS VSS
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* 7 DAT0 MISO
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*/
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#define MMC_nCS CARD_DAT3
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#define MMC_MOSI CARD_CMD
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#define MMC_CLK CARD_CLK
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#define MMC_MISO CARD_DAT0
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void mmc_select(void)
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{
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CLR(MMC_nCS);
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}
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void mmc_deselect(void)
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{
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SET(MMC_nCS);
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}
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uint8_t mmc_recv(void)
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{
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uint8_t i, v = 0;
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SET(MMC_MOSI);
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for (i = 0; i != 8; i++) {
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SET(MMC_CLK);
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v = (v << 1) | PIN(MMC_MISO);
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CLR(MMC_CLK);
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}
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return v;
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}
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void mmc_send(uint8_t v)
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{
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uint8_t i;
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for (i = 0; i != 8; i++) {
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if (v & 0x80)
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SET(MMC_MOSI);
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else
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CLR(MMC_MOSI);
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SET(MMC_CLK);
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CLR(MMC_CLK);
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v <<= 1;
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}
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}
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void mmc_activate(void)
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{
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SET(MMC_nCS);
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CLR(MMC_CLK);
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OUT(MMC_nCS);
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SET(MMC_MOSI);
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SET(MMC_CLK); /* for pre-charging */
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OUT(MMC_MOSI);
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OUT(MMC_CLK);
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IN(MMC_MISO);
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_delay_ms(100); /* allow card to pre-charge, to limit inrush current */
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CLR(CARD_nPWR);
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_delay_ms(10);
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}
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void mmc_deactivate(void)
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{
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CLR(MMC_CLK);
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CLR(MMC_nCS);
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CLR(MMC_MOSI);
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CLR(MMC_MISO);
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SET(CARD_nPWR);
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_delay_ms(10);
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OUT(MMC_MISO);
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}
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