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#include <xc.h>
#include <stdbool.h>
#include <stdint.h>
#include "system.h"
#include "types.h"
#include "spi.h"
#include "eeprom.h"
// 16-byte page ('C' variant)
#define PAGE_SIZE 16u
// Write cycle time = 5ms
// 5ms / (4*Tosc) = 60000
#define WRITE_DELAY 60000u
#define BAILOUT 10u
// 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
};
static U8
readStatus(void) {
U8 status;
EEPROM_CS = 0;
(void)spiTx(CMD_READ_STATUS);
status = spiTx(0x00);
EEPROM_CS = 1;
return status;
}
static Status
writeEnable(void) {
EEPROM_CS = 0;
(void)spiTx(CMD_WRITE_ENABLE);
EEPROM_CS = 1;
return (readStatus() & STATUS_WEL) ? OK : FAIL;
}
static void
writeDisable(void) {
EEPROM_CS = 0;
(void)spiTx(CMD_WRITE_DISABLE);
EEPROM_CS = 1;
}
void
eepromInit(void) {
EEPROM_CS_TRIS = OUT;
EEPROM_CS = 1;
writeDisable();
}
// Wait for pending write to finish
static Status
waitForWrite(void) {
U8 status, k;
status = readStatus();
for (k = 0u; (status & STATUS_WIP) && (k < BAILOUT); k++) {
_delay(WRITE_DELAY);
status = readStatus();
}
return (k < BAILOUT) ? OK : FAIL;
}
static void
spiTxAddr(U16 addr) {
(void)spiTx((addr>>8u) & 0xFF); // MSB
(void)spiTx((addr>>0u) & 0xFF); // LSB
}
static bool
isPageStart(U16 addr) {
return (addr % PAGE_SIZE) == 0;
}
Status
eepromWrite(U16 addr, U8 *data, U8 size) {
Status status;
// Wait for pending write to finish
status = waitForWrite();
if (status != OK) {
return FAIL; // timed out
}
// Set write-enable
status = writeEnable();
if (status != OK) {
return FAIL;
}
// Write
EEPROM_CS = 0;
(void)spiTx(CMD_WRITE);
spiTxAddr(addr);
while (size--) {
(void)spiTx(*data);
data++;
addr++;
// Check if write crosses page boundary
if (isPageStart(addr) && size) {
// Write current page to memory
EEPROM_CS = 1;
status = waitForWrite();
if (status != OK) {
return FAIL; // timed out
}
status = writeEnable();
if (status != OK) {
return FAIL;
}
EEPROM_CS = 0;
// Start next page
(void)spiTx(CMD_WRITE);
spiTxAddr(addr);
}
}
EEPROM_CS = 1;
return OK;
}
Status
eepromRead(U16 addr, U8 *data, U8 size) {
Status status;
// Wait for pending write to finish
status = waitForWrite();
if (status != OK) {
return FAIL; // timed out
}
// Read
EEPROM_CS = 0;
(void)spiTx(CMD_READ);
spiTxAddr(addr);
while (size--) {
*data = spiTx(0x00);
data++;
}
EEPROM_CS = 1;
return OK;
}
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