added eeprom read/write code

Only single bytes can be read or written, page read/write will follow.
Added testcode in main.c to write a value to the EEPROM and read+verify
it.

Makefile

@@ -21,6 +21,7 @@ OBJS = main.o
 
 VPATH +=
 OBJS +=
+OBJS += eeprom/eeprom.o
 LIBS += core/libcore.a lcd/libfont.a
 
 ##########################################################################

eeprom/eeprom.c

@@ -0,0 +1,68 @@
+#include "i2c/i2c.h"
+#include "eeprom.h"
+
+uint8_t eeprom_ready() {
+    uint32_t state;
+
+    I2CMasterBuffer[0] = EEPROM_BASE_ADDR; // Slave address, page 0, write
+    I2CWriteLength = 1; // just write the slave address and stop
+    I2CReadLength = 0;
+
+    state = i2cEngine();
+
+    if (state == I2CSTATE_ACK) {
+        return 1; // ready for next operation
+    } else {
+        return 0;
+    }
+}
+
+uint8_t eeprom_write_byte(uint8_t page_addr, uint8_t byte_addr, uint8_t value) {
+    uint8_t i2c_addr;
+    uint8_t intern_byte_addr;
+    uint32_t state;
+
+    // calculate our addresses with evil bitshift magic
+    i2c_addr = EEPROM_BASE_ADDR | (page_addr >> 3) & 0xFE; // bits 7-4 = base address, 3-1 = bits 6-4 of page address, 0 = R/W
+    intern_byte_addr = (page_addr << 4) | (byte_addr & 0x0F); // bits 7-4 = bits 3-0 of page address, 3-0 = lower 4 bits of byte address
+
+    I2CMasterBuffer[0] = i2c_addr;
+    I2CMasterBuffer[1] = intern_byte_addr;
+    I2CMasterBuffer[2] = value;
+    I2CWriteLength = 3;
+    I2CReadLength = 0;
+
+    state = i2cEngine();
+
+    if (state == I2CSTATE_ACK) {
+        return 1; // ready for next operation
+    } else {
+        return 0;
+    }
+}
+
+uint8_t eeprom_read_byte(uint8_t page_addr, uint8_t byte_addr, uint8_t *value) {
+    uint8_t i2c_addr;
+    uint8_t intern_byte_addr;
+    uint32_t state;
+
+    // calculate our addresses with evil bitshift magic
+    i2c_addr = EEPROM_BASE_ADDR | (page_addr >> 3) & 0xFE; // bits 7-4 = base address, 3-1 = bits 6-4 of page address, 0 = R/W
+    intern_byte_addr = (page_addr << 4) | (byte_addr & 0x0F); // bits 7-4 = bits 3-0 of page address, 3-0 = lower 4 bits of byte address
+
+    I2CMasterBuffer[0] = i2c_addr;
+    I2CMasterBuffer[1] = intern_byte_addr;
+    I2CMasterBuffer[2] = i2c_addr | READ_WRITE;
+    I2CWriteLength = 2;
+    I2CReadLength = 1;
+
+    state = i2cEngine();
+
+    if (state == I2CSTATE_ACK) {
+        *value = I2CSlaveBuffer[0];
+        return 1; // ready for next operation
+    } else {
+        return 0;
+    }
+}
+

eeprom/eeprom.h

@@ -0,0 +1,10 @@
+#ifndef _EEPROM_H
+#define _EEPROM_H 1
+
+#define EEPROM_BASE_ADDR 0xA0
+
+uint8_t eeprom_ready();
+uint8_t eeprom_write_byte(uint8_t page_addr, uint8_t byte_addr, uint8_t value);
+uint8_t eeprom_read_byte(uint8_t page_addr, uint8_t byte_addr, uint8_t *value);
+
+#endif /* _EEPROM_H */

main.c

@@ -22,6 +22,8 @@ void ReinvokeISP(void);
 #include <lcd/smallfonts.h>
 #include <lcd/ubuntu18.h>
 
+#include "core/i2c/i2c.h"
+#include "eeprom/eeprom.h"
 
 /**************************************************************************/
 
@@ -33,6 +35,9 @@ int main(void)
   //enable clocks to adc and watchdog
   pmuInit();
 
+  //enable I2C
+  i2cInit(I2CMASTER);
+
   uint32_t currentSecond, lastSecond;
   currentSecond = lastSecond = 0;
   
@@ -115,13 +120,16 @@ int main(void)
 
 	static FONT fonts[]=
 	{
-	 & Font_8x8,
-	 & Font_Ubuntu18pt, // 3 byte-font
 	 & Font_7x8, 
+	 & Font_Ubuntu18pt, // 3 byte-font
+	 & Font_8x8,
 	};
 	int fontctr=0;
 	yctr=18;
 
+    uint8_t written = 0;
+    uint8_t eeprom_val = 0;
+
   while (1)
   {
     display(j);
@@ -136,7 +144,34 @@ int main(void)
 	*/
 
 	font=fonts[fontctr];
-	DoString(1,yctr,"Hey Y!");
+	//DoString(1,yctr,"Hey Y!");
+
+    if (!written) {
+        if (eeprom_ready()) {
+            if (eeprom_write_byte(127,15,42)) {
+                DoString(1, yctr, "Write OK!");
+                written++;
+            } else {
+                DoString(1, yctr, "Write NOK!");
+            }
+        } else {
+            DoString(1, yctr, "NOT READY!");
+        }
+    } else {
+        if (eeprom_ready()) {
+            if (eeprom_read_byte(127,15,&eeprom_val)) {
+                if (eeprom_val == 42) {
+                    DoString(1, yctr, "verified!");
+                } else {
+                    DoString(1, yctr, "failed!");
+                }
+            } else {
+                DoString(1, yctr, "Read NOK!");
+            }
+        } else {
+            DoString(1, yctr, "NOT READY!!");
+        }
+    }
 
 	if(1 && gpioGetValue(3,3)==0){
 		gpioSetValue (CFG_LED_PORT, CFG_LED_PIN, CFG_LED_ON);