Merge pull request #2 from pilotak/master

mBed online compiler fix + struct example

README.md

@@ -9,6 +9,8 @@ EEPROM devices support much higher read/write cycles than flash based memory, at
 More info on EEPROM can be found on wikipedia:
 https://en.wikipedia.org/wiki/EEPROM
 
+## Basic example
+
 ``` cpp
 // Here's an example using a 24LC256 on a GR PEACH
 #include "mbed.h"
@@ -42,3 +44,58 @@ int main() {
 }
 ```
 
+## Saving struct example
+``` cpp
+// Here's an example using a 24LC256 to store a C struct
+#include "mbed.h"
+#include "I2CEEBlockDevice.h"
+
+#define BLOCK_SIZE 32
+
+// Create EEPROM device on I2C bus with 32kbytes of memory
+I2CEEBlockDevice i2cee(P0_0, P0_1, 0xA0, 32*1024, BLOCK_SIZE);
+
+uint8_t setting_block_size;
+
+struct t_setting {
+    uint8_t version;
+    char name[20];
+} setting = {
+    1,
+    "Hello World!"
+};
+
+int main() {
+    printf("i2cee struct test\n");
+
+     // No. of bytes to be stored, but topped up to be multiplied by block size
+    unsigned int setting_block_size = ceil(sizeof(setting)/(double)BLOCK_SIZE)*BLOCK_SIZE;
+
+    // Temporary buffer
+    char *buffer = (char*)malloc(setting_block_size);
+
+    // Initialize the device
+    i2cee.init();
+
+    // Save struct to EEPROM
+    printf("\nSaving struct version: %u, name: %s\n", setting.version, setting.name);
+    memcpy(buffer, &setting, sizeof(setting));
+    i2cee.program(buffer, 0, setting_block_size);
+
+    // Get back what was stored
+    t_setting tmp; //Re-make the struct
+    memset(buffer, 0, sizeof(buffer)); // empty buffer, not nessesary but helps when debugging
+
+    if (i2cee.read(buffer, 0, setting_block_size ) == 0){ // get data into buffer
+        // Convert what we read into struct
+        memcpy(&tmp, buffer, sizeof(tmp)); // copy only size of struct not setting_block_size
+        printf("\nTemporary struct version: %u, name: %s\n", tmp.version, tmp.name);
+    } else {
+        printf("Error when reading\n");
+    }
+
+    // Deinitialize the device
+    i2cee.deinit();
+}
+```
+