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/*
* PiLC HAT firmware
* 24Cxx EEPROM emulation
*
* Copyright (c) 2016 Michael Buesch <m@bues.ch>
*
* 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; either version 2 of the License, or
* (at your option) any later version.
*
* 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "eepemu_24cxx.h"
#include "i2c_slave.h"
#include <string.h>
#include <avr/eeprom.h>
/* Default to: emulated page size = 32 bytes. */
#ifndef EE24CXX_PAGE_MASK
# define EE24CXX_PAGE_MASK ((uint16_t)(32 - 1))
#endif
enum ee24cxx_state {
EE24CXX_IDLE,
EE24CXX_WRADDRLO,
EE24CXX_ADDRCOMPLETE,
};
struct ee24cxx_context {
enum ee24cxx_state state;
uint16_t word_addr;
bool write_en;
};
static struct ee24cxx_context ee24cxx;
#ifdef EEPEMU_24CXX_CONTENT_IN_FLASH
# define EEPEMU_DEF_ATTR const __flash
# define EEPEMU_DECL_ATTR const __flash
# define EEPEMU_IMG_SIZE
#else
# define EEPEMU_DEF_ATTR EEMEM
# define EEPEMU_DECL_ATTR
# define EEPEMU_IMG_SIZE (E2END + 1)
#endif
#include "eepemu_24cxx_content.c"
#define EE24CXX_ADDR_MASK (EEPEMU_24CXX_SIZE - 1)
static void ee24cxx_busy_wait(void)
{
#ifndef EEPEMU_24CXX_CONTENT_IN_FLASH
eeprom_busy_wait();
#endif
}
static uint8_t ee24cxx_read_byte(uint8_t EEPEMU_DECL_ATTR *mem)
{
#ifdef EEPEMU_24CXX_CONTENT_IN_FLASH
return *mem;
#else
return eeprom_read_byte(mem);
#endif
}
static void ee24cxx_write_byte(uint8_t EEPEMU_DECL_ATTR *mem, uint8_t data)
{
#ifndef EEPEMU_24CXX_CONTENT_IN_FLASH
eeprom_write_byte(mem, data);
#endif
}
void ee24cxx_set_we(bool write_enable)
{
struct ee24cxx_context *ee = &ee24cxx;
#ifdef EEPEMU_24CXX_CONTENT_IN_FLASH
write_enable = false;
#endif
ee->write_en = write_enable;
}
bool ee24cxx_get_we(void)
{
struct ee24cxx_context *ee = &ee24cxx;
return ee->write_en;
}
static uint8_t ee24cxx_transmit(bool start)
{
struct ee24cxx_context *ee = &ee24cxx;
uint8_t ret = 0;
switch (ee->state) {
case EE24CXX_IDLE:
/* current-address-read. */
ret = ee->word_addr & 0xFF;
break;
case EE24CXX_ADDRCOMPLETE:
/* data read. */
ee24cxx_busy_wait();
if (ee->word_addr < sizeof(eepemu_24cxx_content))
ret = ee24cxx_read_byte(&eepemu_24cxx_content[ee->word_addr]);
else
ret = 0xFF;
ee->word_addr = (ee->word_addr + 1) & EE24CXX_ADDR_MASK;
break;
case EE24CXX_WRADDRLO:
/* error: address not complete. */
break;
}
return ret;
}
static bool ee24cxx_receive(bool start, uint8_t data)
{
struct ee24cxx_context *ee = &ee24cxx;
bool ret = false;
if (start)
ee->state = EE24CXX_IDLE;
switch (ee->state) {
case EE24CXX_IDLE:
/* address high byte write. */
ee->word_addr = (ee->word_addr & 0x00FF) |
((uint16_t)data << 8);
ee->word_addr &= EE24CXX_ADDR_MASK;
ee->state = EE24CXX_WRADDRLO;
ret = true;
break;
case EE24CXX_WRADDRLO:
/* address low byte write. */
ee->word_addr = (ee->word_addr & 0xFF00) |
((uint16_t)data);
ee->word_addr &= EE24CXX_ADDR_MASK;
ee->state = EE24CXX_ADDRCOMPLETE;
if (ee->write_en)
ret = true;
break;
case EE24CXX_ADDRCOMPLETE:
/* data write. */
if (ee->write_en) {
ee24cxx_busy_wait();
ee24cxx_write_byte(&eepemu_24cxx_content[ee->word_addr],
data);
}
ee->word_addr = (ee->word_addr & ~EE24CXX_PAGE_MASK) |
((ee->word_addr + 1) & EE24CXX_PAGE_MASK);
ret = true;
break;
}
return ret;
}
static const struct i2c_slave_ops __flash ee24cxx_i2c_slave_ops = {
.transmit = ee24cxx_transmit,
.receive = ee24cxx_receive,
};
void ee24cxx_init(void)
{
#ifndef EEPEMU_24CXX_CONTENT_IN_FLASH
build_assert(sizeof(eepemu_24cxx_content) < E2END);
#endif
memset(&ee24cxx, 0, sizeof(ee24cxx));
ee24cxx.state = EE24CXX_IDLE;
i2cs_add_slave(EEPEMU_24CXX_ADDR, &ee24cxx_i2c_slave_ops);
}
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