1 files changed, 123 insertions, 0 deletions
diff --git a/sw/eeprom.c b/sw/eeprom.c
new file mode 100644
index 0000000..ce8aed7
--- /dev/null
+++ b/sw/eeprom.c
@@ -0,0 +1,123 @@
+#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
+}