diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..496ee2c
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.DS_Store
\ No newline at end of file
diff --git a/README.md b/README.md
index 898bdbe..d0b53e2 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,95 @@
-# zh_avr_i2c
+# FreeRTOS based AVR library for I2C bus
 
-AVR library for I2C bus.
\ No newline at end of file
+## Features
+
+1. Simple read and write data.
+
+## Dependencies
+
+1. [zh_avr_free_rtos](http://git.zh.com.ru/avr_libraries/zh_avr_free_rtos)
+
+## Using
+
+In an existing project, run the following command to install the component:
+
+```text
+cd ../your_project/lib
+git clone http://git.zh.com.ru/avr_libraries/zh_avr_free_rtos
+git clone http://git.zh.com.ru/avr_libraries/zh_avr_i2c
+```
+
+In the application, add the component:
+
+```c
+#include "zh_avr_i2c.h"
+```
+
+## Example
+
+Master read and write data:
+
+```c
+#include "avr/io.h"
+#include "stdio.h"
+#include "zh_avr_i2c.h"
+
+#define BAUD_RATE 9600
+#define BAUD_PRESCALE (F_CPU / 16 / BAUD_RATE - 1)
+
+int usart(char byte, FILE *stream)
+{
+    while ((UCSR0A & (1 << UDRE0)) == 0)
+    {
+    }
+    UDR0 = byte;
+    return 0;
+}
+FILE uart = FDEV_SETUP_STREAM(usart, NULL, _FDEV_SETUP_WRITE);
+
+void i2c_example_task(void *pvParameters)
+{
+    zh_avr_i2c_master_init(false);
+    for (;;)
+    {
+        avr_err_t err = zh_avr_i2c_master_probe(0x38, 100 / portTICK_PERIOD_MS);
+        if (err == AVR_OK)
+        {
+            uint8_t data_send = 111;
+            uint8_t data_read = 0;
+            printf("Data Send %d.\n", data_send);
+            zh_avr_i2c_master_transmit(0x38, (uint8_t *)&data_send, sizeof(data_send), 100 / portTICK_PERIOD_MS);
+            zh_avr_i2c_master_receive(0x38, (uint8_t *)&data_read, sizeof(data_read), 100 / portTICK_PERIOD_MS);
+            printf("Data Read %d.\n", data_read);
+            data_send = 55;
+            printf("Data Send %d.\n", data_send);
+            zh_avr_i2c_master_transmit(0x38, (uint8_t *)&data_send, sizeof(data_send), 100 / portTICK_PERIOD_MS);
+            zh_avr_i2c_master_receive(0x38, (uint8_t *)&data_read, sizeof(data_read), 100 / portTICK_PERIOD_MS);
+            printf("Data Read %d.\n", data_read);
+            data_send = 14;
+            printf("Data Send %d.\n", data_send);
+            zh_avr_i2c_master_transmit(0x38, (uint8_t *)&data_send, sizeof(data_send), 100 / portTICK_PERIOD_MS);
+            zh_avr_i2c_master_receive(0x38, (uint8_t *)&data_read, sizeof(data_read), 100 / portTICK_PERIOD_MS);
+            printf("Data Read %d.\n", data_read);
+        }
+        else
+        {
+            printf("Device Not Found.\n");
+        }
+        printf("Task Remaining Stack Size %d.\n", uxTaskGetStackHighWaterMark(NULL));
+        vTaskDelay(5000 / portTICK_PERIOD_MS);
+    }
+    vTaskDelete(NULL);
+}
+
+int main(void)
+{
+    UBRR0H = (BAUD_PRESCALE >> 8);
+    UBRR0L = BAUD_PRESCALE;
+    UCSR0B = (1 << RXEN0) | (1 << TXEN0);
+    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
+    stdout = &uart;
+    xTaskCreate(i2c_example_task, "i2c example task", 110, NULL, tskIDLE_PRIORITY, NULL);
+    vTaskStartScheduler();
+    return 0;
+}
+```
diff --git a/include/zh_avr_i2c.h b/include/zh_avr_i2c.h
new file mode 100644
index 0000000..ce54695
--- /dev/null
+++ b/include/zh_avr_i2c.h
@@ -0,0 +1,80 @@
+#pragma once
+
+#include "FreeRTOS.h"
+#include "event_groups.h"
+#include "avr/io.h"
+#include "avr/interrupt.h"
+#include "stdbool.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+	typedef enum
+	{
+		AVR_FAIL = -1,
+		AVR_OK,
+		AVR_ERR_NO_MEM,
+		AVR_ERR_INVALID_ARG,
+		AVR_ERR_INVALID_STATE,
+		AVR_ERR_INVALID_SIZE,
+		AVR_ERR_NOT_FOUND,
+		AVR_ERR_NOT_SUPPORTED,
+		AVR_ERR_TIMEOUT,
+		AVR_ERR_INVALID_RESPONSE,
+		AVR_ERR_INVALID_CRC,
+		AVR_ERR_INVALID_VERSION,
+		AVR_ERR_NOT_FINISHED,
+		AVR_ERR_NOT_ALLOWED
+	} avr_err_t;
+
+	/**
+	 * @brief Initialize I2C bus.
+	 *
+	 * @param[in] pullup Using internal pullup resistors.
+	 *
+	 * @return AVR_OK if success or an error code otherwise.
+	 */
+	avr_err_t zh_avr_i2c_master_init(const bool pullup);
+
+	/**
+	 * @brief Probe I2C address.
+	 *
+	 * @param[in] addr Address I2C device.
+	 * @param[in] xTicksToWait Wait timeout in FreeRTOS ticks.
+	 *
+	 * @return AVR_OK if success or an error code otherwise.
+	 */
+	avr_err_t zh_avr_i2c_master_probe(const uint8_t addr, TickType_t xTicksToWait);
+
+	/**
+	 * @brief Send data to I2C address.
+	 *
+	 * @param[in] addr Address I2C device.
+	 * @param[in] data Pointer to data for send.
+	 * @param[in] size Data size.
+	 * @param[in] xTicksToWait Wait timeout in FreeRTOS ticks.
+	 *
+	 * @return AVR_OK if success or an error code otherwise.
+	 */
+	avr_err_t zh_avr_i2c_master_transmit(const uint8_t addr, uint8_t *data, uint8_t size, TickType_t xTicksToWait);
+
+	/**
+	 * @brief Read data from I2C address.
+	 *
+	 * @param[in] addr Address I2C device.
+	 * @param[out] data Pointer to buffer for read.
+	 * @param[in] size Data size.
+	 * @param[in] xTicksToWait Wait timeout in FreeRTOS ticks.
+	 *
+	 * @return AVR_OK if success or an error code otherwise.
+	 */
+	avr_err_t zh_avr_i2c_master_receive(const uint8_t addr, uint8_t *data, uint8_t size, TickType_t xTicksToWait);
+
+	avr_err_t zh_avr_i2c_master_transmit_register(const uint8_t addr, uint16_t *reg, uint8_t *data, uint8_t size, TickType_t xTicksToWait); // To Do
+	avr_err_t zh_avr_i2c_master_receive_register(const uint8_t addr, uint16_t *reg, uint8_t *data, uint8_t size, TickType_t xTicksToWait);	// To Do
+
+#ifdef __cplusplus
+}
+#endif
\ No newline at end of file
diff --git a/version.txt b/version.txt
new file mode 100644
index 0000000..afaf360
--- /dev/null
+++ b/version.txt
@@ -0,0 +1 @@
+1.0.0
\ No newline at end of file
diff --git a/zh_avr_i2c.c b/zh_avr_i2c.c
new file mode 100644
index 0000000..fbc8e47
--- /dev/null
+++ b/zh_avr_i2c.c
@@ -0,0 +1,216 @@
+#include "zh_avr_i2c.h"
+
+#define ZH_ERROR_CHECK(cond, err, ...) \
+	if (!(cond))                       \
+	{                                  \
+		return err;                    \
+	}
+
+#define I2C_OK 0x01
+#define I2C_NACK 0x02
+#define I2C_COLLISION 0x04
+#define I2C_BUS_FAIL 0x08
+
+#define I2C_START ((1 << TWINT) | (1 << TWEN) | (1 << TWIE))
+#define I2C_MASTER_READ 1
+#define I2C_MASTER_WRITE 0
+
+typedef enum
+{
+	MASTER_WRITE,
+	MASTER_READ,
+	MASTER_WRITE_REG,
+	MASTER_READ_REG
+} _work_mode_t;
+
+avr_err_t _zh_avr_i2c_master_start(TickType_t xTicksToWait);
+
+static EventGroupHandle_t _event_group_handle = NULL;
+static uint8_t _target_i2c_address = 0;
+volatile static uint8_t _work_mode = 0;
+volatile static uint8_t *_master_data = NULL;
+volatile static uint8_t _master_data_size = 0;
+static bool _master_is_initialized = false;
+
+avr_err_t zh_avr_i2c_master_init(const bool pullup)
+{
+	_event_group_handle = xEventGroupCreate();
+	ZH_ERROR_CHECK(_event_group_handle != NULL, AVR_ERR_NO_MEM);
+	cli();
+	DDRC &= ~(1 << PORTC5 | 1 << PORTC4);
+	if (pullup == true)
+	{
+		PORTC |= 1 << PORTC5 | 1 << PORTC4;
+	}
+	TWBR = ((F_CPU / 100000) - 16) / 2;
+	TWSR = 0xF8;
+	sei();
+	_master_is_initialized = true;
+	return AVR_OK;
+}
+
+avr_err_t zh_avr_i2c_master_probe(const uint8_t addr, TickType_t xTicksToWait)
+{
+	uint8_t temp = 0;
+	return zh_avr_i2c_master_transmit(addr, &temp, sizeof(temp), xTicksToWait);
+}
+
+avr_err_t zh_avr_i2c_master_transmit(const uint8_t addr, uint8_t *data, uint8_t size, TickType_t xTicksToWait)
+{
+	ZH_ERROR_CHECK(data != NULL || size > 0, AVR_ERR_INVALID_ARG);
+	ZH_ERROR_CHECK(_master_is_initialized == true, AVR_ERR_INVALID_STATE);
+	_work_mode = MASTER_WRITE;
+	_target_i2c_address = addr;
+	_master_data = data;
+	_master_data_size = size;
+	return _zh_avr_i2c_master_start(xTicksToWait);
+}
+
+avr_err_t zh_avr_i2c_master_receive(const uint8_t addr, uint8_t *data, uint8_t size, TickType_t xTicksToWait)
+{
+	ZH_ERROR_CHECK(data != NULL || size > 0, AVR_ERR_INVALID_ARG);
+	ZH_ERROR_CHECK(_master_is_initialized == true, AVR_ERR_INVALID_STATE);
+	_work_mode = MASTER_READ;
+	_target_i2c_address = addr;
+	_master_data = data;
+	_master_data_size = size;
+	return _zh_avr_i2c_master_start(xTicksToWait);
+}
+
+avr_err_t zh_avr_i2c_master_transmit_register(const uint8_t addr, uint16_t *reg, uint8_t *data, uint8_t size, TickType_t xTicksToWait)
+{
+	// To Do.
+	return AVR_OK;
+}
+avr_err_t zh_avr_i2c_master_receive_register(const uint8_t addr, uint16_t *reg, uint8_t *data, uint8_t size, TickType_t xTicksToWait)
+{
+	// To Do.
+	return AVR_OK;
+}
+
+avr_err_t _zh_avr_i2c_master_start(TickType_t xTicksToWait)
+{
+	TWCR = I2C_START | (1 << TWSTA);
+	EventBits_t bits = xEventGroupWaitBits(_event_group_handle, I2C_OK | I2C_NACK | I2C_COLLISION | I2C_BUS_FAIL, pdTRUE, pdFALSE, xTicksToWait);
+	if ((bits & I2C_OK) != 0)
+	{
+		return AVR_OK;
+	}
+	else if ((bits & I2C_NACK) != 0)
+	{
+		return AVR_ERR_INVALID_RESPONSE;
+	}
+	else
+	{
+		return AVR_FAIL;
+	}
+}
+
+ISR(TWI_vect)
+{
+	BaseType_t xHigherPriorityTaskWoken = pdFALSE;
+	switch (TWSR & 0xF8)
+	{
+	case 0x00: // Bus error.
+		TWCR = I2C_START | (1 << TWSTO);
+		xEventGroupSetBitsFromISR(_event_group_handle, I2C_BUS_FAIL, &xHigherPriorityTaskWoken);
+		break;
+	case 0x08: // A START condition has been transmitted.
+		switch (_work_mode)
+		{
+		case MASTER_WRITE:
+		case MASTER_WRITE_REG:
+		case MASTER_READ_REG:
+			TWDR = (_target_i2c_address << 1) | I2C_MASTER_WRITE;
+			break;
+		case MASTER_READ:
+			TWDR = (_target_i2c_address << 1) | I2C_MASTER_READ;
+			break;
+		default:
+			break;
+		}
+		TWCR = I2C_START;
+		break;
+	case 0x10: // A repeated START condition has been transmitted.
+		// To Do.
+		break;
+	case 0x18: // SLA+W has been transmitted. ACK has been received.
+		TWDR = *(_master_data++);
+		--_master_data_size;
+		TWCR = I2C_START;
+		break;
+	case 0x20: // SLA+W has been transmitted. NACK has been received.
+		TWCR = I2C_START | (1 << TWSTO);
+		xEventGroupSetBitsFromISR(_event_group_handle, I2C_NACK, &xHigherPriorityTaskWoken);
+		break;
+	case 0x28: // Data byte has been transmitted. ACK has been received.
+		if (_master_data_size-- == 0)
+		{
+			TWCR = I2C_START | (1 << TWSTO);
+			xEventGroupSetBitsFromISR(_event_group_handle, I2C_OK, &xHigherPriorityTaskWoken);
+		}
+		else
+		{
+			TWDR = *(_master_data++);
+			TWCR = I2C_START;
+		}
+		break;
+	case 0x30: // Data byte has been transmitted. NACK has been received.
+		TWCR = I2C_START | (1 << TWSTO);
+		xEventGroupSetBitsFromISR(_event_group_handle, I2C_NACK, &xHigherPriorityTaskWoken);
+		break;
+	case 0x38: // Arbitration lost in SLA+W or data bytes. Arbitration lost in SLA+R or NACK bit.
+		TWCR = I2C_START | (1 << TWSTO);
+		xEventGroupSetBitsFromISR(_event_group_handle, I2C_COLLISION, &xHigherPriorityTaskWoken);
+		break;
+	case 0x40: // SLA+R has been transmitted. ACK has been received.
+		switch (_work_mode)
+		{
+		case MASTER_WRITE:
+			break;
+		case MASTER_READ:
+			if (_master_data_size == 1)
+			{
+				TWCR = I2C_START;
+			}
+			else
+			{
+				TWCR = I2C_START | (1 << TWEA);
+			}
+			break;
+		case MASTER_WRITE_REG:
+			break;
+		case MASTER_READ_REG:
+			break;
+		default:
+			break;
+		}
+		break;
+	case 0x48: // SLA+R has been transmitted. NACK has been received.
+		TWCR = I2C_START | (1 << TWSTO);
+		xEventGroupSetBitsFromISR(_event_group_handle, I2C_NACK, &xHigherPriorityTaskWoken);
+		break;
+	case 0x50: // Data byte has been received. ACK has been returned.
+		*(_master_data++) = TWDR;
+		if (--_master_data_size == 1)
+		{
+			TWCR = I2C_START;
+		}
+		else
+		{
+			TWCR = I2C_START | (1 << TWEA);
+		}
+		break;
+	case 0x58: // Data byte has been received. NACK has been returned.
+		*(_master_data) = TWDR;
+		TWCR = I2C_START | (1 << TWSTO);
+		xEventGroupSetBitsFromISR(_event_group_handle, I2C_OK, &xHigherPriorityTaskWoken);
+		break;
+	default:
+		break;
+	}
+	if (xHigherPriorityTaskWoken == pdTRUE)
+	{
+		portYIELD();
+	};
+}
\ No newline at end of file