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# 1.1.10.1.2 Using The Library

The AT24 driver provides non-blocking API's to read, write AT24 EEPROM.

The AT24 driver can be used in following ways:

- To perform reads and writes from/to any EEPROM memory address, with number of bytes spanning multiple pages

- To perform page write to AT24 EEPROM. Here, the memory start address must be aligned to the page boundary

- To interface with the Memory driver to perform block operations on the AT24 EEPROM

- Application can either register a callback to get notified once the data transfer is complete or can poll the status of the data transfer

Example application to Write and Read AT24 EEPROM

    #define BUFFER_SIZE     512
    #define MEM_ADDRESS     0x0

    APP_DATA CACHE_ALIGN appData;

    static uint32_t erase_index = 0;
    static uint32_t write_index = 0;

    static void APP_EEPROM_EventHandler(DRV_AT24_TRANSFER_STATUS event, uintptr_t context)
    {
        switch(event)
        {
            case DRV_AT24_TRANSFER_STATUS_COMPLETED:
            {
                appData.isTransferDone = true;
                break;
            }

            case DRV_AT24_TRANSFER_STATUS_ERROR:
            default:
            {
                appData.isTransferDone = false;
                appData.state = APP_STATE_ERROR;
                break;
            }
        }
    }

    void APP_Initialize ( void )
    {
        uint32_t i = 0;

        /* Place the App state machine in its initial state. */
        appData.state = APP_STATE_INIT;

        for (i = 0; i < BUFFER_SIZE; i++)
        {
            appData.writeBuffer[i] = i;
        }

        appData.isTransferDone = false;
    }

    void APP_Tasks ( void )
    {
        uint32_t i;

        /* Check the application's current state. */
        switch ( appData.state )
        {
            /* Application's initial state. */
            case APP_STATE_INIT:
            {
                appData.drvHandle = DRV_AT24_Open(DRV_AT24_INDEX, DRV_IO_INTENT_READWRITE);

                if (appData.drvHandle != DRV_HANDLE_INVALID)
                {
                    DRV_AT24_EventHandlerSet(appData.drvHandle, APP_EEPROM_EventHandler, 0);

                    appData.state = APP_STATE_WRITE;
                }
                else
                {
                    appData.state = APP_STATE_ERROR;
                }
                break;
            }

            case APP_STATE_WRITE:
            {
                /* Set the next state first as callback may be fired before the state
                 * is changed; potentially over-writing error state set from the callback */
                appData.state = APP_STATE_WAIT_WRITE_COMPLETE;

                if (DRV_AT24_Write(appData.drvHandle,
                        appData.writeBuffer,
                        BUFFER_SIZE,
                        AT24_EEPROM_MEM_ADDR) == false)
                {
                    appData.state = APP_STATE_ERROR;
                }
                break;
            }

            case APP_STATE_WAIT_WRITE_COMPLETE:
            {
                if (appData.isTransferDone == true)
                {
                    appData.isTransferDone = false;
                    appData.state = APP_STATE_READ;
                }
                break;
            }

            case APP_STATE_READ:
            {
                appData.state = APP_STATE_WAIT_READ_COMPLETE;

                if (DRV_AT24_Read(appData.drvHandle,
                        appData.readBuffer,
                        BUFFER_SIZE,
                        AT24_EEPROM_MEM_ADDR) == false)
                {
                    appData.state = APP_STATE_ERROR;
                }
                break;
            }

            case APP_STATE_WAIT_READ_COMPLETE:
            {
                if (appData.isTransferDone == true)
                {
                    appData.isTransferDone = false;
                    appData.state = APP_STATE_VERIFY;
                }
                break;
            }

            case APP_STATE_VERIFY:
            {
                if (memcmp(appData.writeBuffer, appData.readBuffer, BUFFER_SIZE ) == 0)
                {
                    appData.state = APP_STATE_SUCCESS;
                }
                else
                {
                    appData.state = APP_STATE_ERROR;
                }
                break;
            }

            case APP_STATE_SUCCESS:
            {
                appData.state = APP_STATE_IDLE;
                break;
            }

            case APP_STATE_ERROR:
            {
                appData.state = APP_STATE_IDLE;
                break;
            }

            case APP_STATE_IDLE:
                DRV_AT24_Close(appData.drvHandle);
            default:
            {
                break;
            }
        }
    }