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#include <xc.h>
#include <stdbool.h>
#include <stdint.h>
#include "sys.h"
#include "types.h"
#include "spi.h"
#include "eeprom.h"
// 16-byte page ('C' variant)
#define PAGE_SIZE 16u
// Commands
enum {
CMD_READ = 0x03,
CMD_WRITE = 0x02,
CMD_WRITE_DISABLE = 0x04,
CMD_WRITE_ENABLE = 0x06,
CMD_READ_STATUS = 0x05,
CMD_WRITE_STATUS = 0x01,
};
// Status register masks
enum {
STATUS_WIP = 0x1, // write in progress
STATUS_WEL = 0x2, // write enable latch
STATUS_BP0 = 0x4, // block protection 0
STATUS_BP1 = 0x8, // block protection 1
};
// Timing
enum {
TIME_WRITE_CYCLE_MS = 5,
};
void
eepromInit(void) {
EEPROM_CS_TRIS = OUT;
EEPROM_CS = 1;
eepromWriteDisable();
}
void
eepromWriteEnable(void) {
EEPROM_CS = 0;
(void)spiTx(CMD_WRITE_ENABLE);
EEPROM_CS = 1;
}
void
eepromWriteDisable(void) {
EEPROM_CS = 0;
(void)spiTx(CMD_WRITE_DISABLE);
EEPROM_CS = 1;
}
static bool
isWriteInProgress(void) {
U8 status;
EEPROM_CS = 0;
(void)spiTx(CMD_READ_STATUS);
status = spiTx(0x00);
EEPROM_CS = 1;
return status & STATUS_WIP;
}
static void
spiTxAddr(U16 addr) {
(void)spiTx(addr.hi);
(void)spiTx(addr.lo);
}
static bool
isPageStart(U16 addr) {
return (addr.lo % PAGE_SIZE) == 0;
}
void
eepromWrite(U16 addr, U8 *data, U8 size) {
while (isWriteInProgress()) {} // wait for previous write to finish
EEPROM_CS = 0; // pull chip-select low
(void)spiTx(CMD_WRITE);
spiTxAddr(addr);
while (size--) {
(void)spiTx(*data);
data++;
incU16(&addr);
// Check if write crosses page boundary
if (isPageStart(addr) && size) {
// Write current page to memory
EEPROM_CS = 1;
while (isWriteInProgress()) {}
EEPROM_CS = 0;
// Start next page
(void)spiTx(CMD_WRITE);
spiTxAddr(addr);
}
}
EEPROM_CS = 1; // release chip-select
}
void
eepromRead(U16 addr, U8 *data, U8 size) {
EEPROM_CS = 0; // pull chip-select low
(void)spiTx(CMD_READ);
spiTxAddr(addr);
while (size--) {
*data = spiTx(0x00);
data++;
}
EEPROM_CS = 1; // release chip-select
}
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