Added method to set the EEPROM offset where network configuration dat…

…a will be stored.

Existing NET_EEPROM_OFFSET #define removed as it never worked.

README.md

@@ -1,7 +1,10 @@
 NetEEPROM
 =========
 
-Arduino library that reads stores network settings to EEPROM.
+Arduino library that reads stores network settings to EEPROM. This is
+useful to associate a network configuration with a specific Arduino
+board which can then be read by many sketches without having to be
+set in each sketch.
 
 This library stores to EEPROM:
 * the MAC address of the interface
@@ -47,3 +50,18 @@ following line:
 
     NetEeprom.begin();
 
+If you wish to configure the start address in EEPROM where the network
+configuration resides, call the `setEepromOffset()` following method 
+**before** calling any other methods. If you do not call this method, then
+the default EEPROM location set set to 0. To set the network configuration at
+a custom EEPROM offset, use the following code.
+
+    NetEeprom.setEepromOffet(128);
+    byte mac[6] = { 0xCA, 0xFE, 0xBA, 0xBE, 0x00, 0x00 };
+    NetEeprom.writeDhcpConfig(mac);
+
+To read network configuration at a custom EEPROM offset, use the following
+code:
+
+    NetEeprom.setEepromOffset(128);
+    NetEeprom.begin();

keywords.txt

@@ -1,4 +1,5 @@
 NetEEPROM	KEYWORD1
+setEepromOffset KEYWORD2
 begin	KEYWORD2
 writeDhcpConfig	KEYWORD2
 writeManualConfig	KEYWORD2

src/NetEEPROM.cpp

@@ -3,13 +3,21 @@
 #include "Ethernet.h"
 
 
-#define MAC_OFFSET (NET_EEPROM_OFFSET + 1)
+#define MAC_OFFSET (eepromOffset + 1)
 #define DHCP_OFFSET (MAC_OFFSET + 6)
 #define IP_OFFSET (DHCP_OFFSET + 1)
 #define DNS_OFFSET (IP_OFFSET + 4)
 #define GW_OFFSET (DNS_OFFSET + 4)
 #define SUBNET_OFFSET (GW_OFFSET + 4)
 
+NetEEPROM::NetEEPROM(void) {
+  eepromOffset = 0;
+}
+
+void NetEEPROM::setEepromOffset(int offset) {
+  eepromOffset = offset;
+}
+
 void NetEEPROM::begin() {
   delay(250); // For ethernet instantiation
   byte mac[6];
@@ -76,7 +84,7 @@ void NetEEPROM::readSubnet(byte subnet[]) {
 }
 
 int NetEEPROM::checkMagic() {
-  return EEPROM.read(NET_EEPROM_OFFSET) == NET_EEPROM_MAGIC;
+  return EEPROM.read(eepromOffset) == NET_EEPROM_MAGIC;
 }
 
 void NetEEPROM::generateRandomMac(byte mac[]) {
@@ -102,7 +110,7 @@ void NetEEPROM::writeEEPROM(byte data[], int offset, int length) {
 }
 
 void NetEEPROM::writeMac(byte mac[]) {
-  EEPROM.write(NET_EEPROM_OFFSET, NET_EEPROM_MAGIC);
+  EEPROM.write(eepromOffset, NET_EEPROM_MAGIC);
   writeEEPROM(mac, MAC_OFFSET, 6);
 }
 

src/NetEEPROM.h

@@ -6,14 +6,6 @@
  * 24 bytes of EEPROM are required to store the configuration.
  */
 
-/* The EEPROM offset at which the network configuration starts.
- * Sketches can override this by defining NET_EEPROM_OFFSET before
- * importing NetEEPROM.h.
- */
-#ifndef NET_EEPROM_OFFSET
-#define NET_EEPROM_OFFSET 0
-#endif
-
 /* The pin from which an anlog reading will be taken to generate a random MAC. */
 #ifndef NET_RANDOM_ANALOG_PIN
 #define NET_RANDOM_ANALOG_PIN 0
@@ -31,6 +23,15 @@
 class NetEEPROM {
 
   public:
+
+  NetEEPROM();
+
+  /* Sets the location in EEPROM that network configuration data will be
+   * stored. If not called, then it defaults to zero. This method should
+   * generally be called before any other methods.
+   */
+  void setEepromOffset(int offset);
+
   /* Configures the network adapter from settings stored in EEPROM.
    * If no settings can be found in EEPROM then a random MAC address
    * will be generated and the adapter will use DHCP for IP configuration,
@@ -97,6 +98,7 @@ class NetEEPROM {
   void readSubnet(byte subnet[]);
 
   private:
+  int eepromOffset;
   void generateRandomMac(byte mac[]);
   void readEEPROM(byte data[], int offset, int length);
   void writeEEPROM(byte data[], int offset, int length);