diff --git a/docs/helios64/hardware.md b/docs/helios64/hardware.md
index 5a48d57..5563b6f 100644
--- a/docs/helios64/hardware.md
+++ b/docs/helios64/hardware.md
@@ -11,7 +11,7 @@ This block diagram is cited from the RK3399 website documentation. [1](http://op
 ## Connector / Interface List
 
 
-![!Board Legend](/helios64/img/hardware/helios64_board_labeled.png)
+![!Board Legend](/helios64/img/hardware/helios64_board_labeled.jpg)
 
 Name |Peripheral Type|Connector Type|Details
 -----|---------------|--------------|-------
diff --git a/docs/helios64/i2c.md b/docs/helios64/i2c.md
index f9a7a20..50889e4 100644
--- a/docs/helios64/i2c.md
+++ b/docs/helios64/i2c.md
@@ -1,6 +1,124 @@
-### Check I2C Communication
+### I2C Overview
 
-To check if the system can communicate with the I2C device, we should first scan the I2C bus to see if we can detect the device.
+Helios64 support I2C bus for the low-speed communication between devices like microcontrollers, EEPROMs, A/D and D/A converters, I/O interface and other similar peripherals in embedded systems.
+In order to communicate with each I2C slave device you will need an address and communication scenario.
+
+Helios64 board exposes the SoC I2C Bus 1, on header **P1**. Below is the header pin-out.
+
+### I2C bus on Helios64 / RK3399K
+
+The I2C controller on RK3399K support following features:
+
+- 9 on-chip I2C controllers
+- Multi-master I2C operation
+- Support 7bits and 10bits address mode
+- Serial 8bits oriented and bidirectional data transfers can be made
+- Software programmable clock frequency
+- Data on the I2C-bus can be transferred at rates of up to 100 kbit/s in the Standardmode, up to 400 kbit/s in the Fast-mode or up to 1 Mbit/s in Fast-mode Plus.
+
+
+### Internal Bus (system reserved, NOT for user application)
+
+In the implementation, we divide the I2C controller into 2 category.
+The first implementation is for system (internal bus) and the other one is for user application (external).
+Below figure describe the I2C Map inside the board:
+
+Bus 0:
+
+Slave   | Address  | Description|
+------- | ------   |------      |
+RK808-D | 0x1b     |            |
+SYR837  | 0x40     |            |
+SYR838  | 0x41     |            |
+
+
+Bus 2:
+
+Slave   | Address  | Description|
+------- | ------   |------      |
+NCT75   | 0x4c     |            |
+PCA9655 | 0x21     |            |
+
+Bus 4:
+
+Slave   | Address  | Description|
+------- | ------   |------      |
+FUSB302 | 0x22     |            |
+
+Above bus number and also including bus number 1,3,5 are reserved for system use, therefore not accessible to the user.
+
+!!! Warning
+    This bus number and address should not be accessed directly by user. Incorrect configuration can damaged the board!
+
+### External Bus
+
+Helios64 exposed Bus number 7 and 8 of the I2C in **P2** and **P1** pinout, respectively.
+This I2C bus can be connected to the external devices.
+
+As described on below figure of [I2C](/helios64/img/hardware/i2c_pinout.png) (pin header number *3* and *4*), user can access the device at bus number 7. 
+For the [UEXT](/helios64/img/hardware/UEXT_pinout.png) (pin header number *5* and *6*), user can access the device at bus number 8.
+
+All the I2C bus in the board are using voltage level of 3.3V, please notice Helios64 is integrated with level translator and pull up resistor.
+
+#### I2C at P1 Header
+
+![I2C Pinout](/helios64/img/hardware/i2c_pinout.png)
+
+This I2C device working with 3 pin bus (SDA, SCK, and GND), and also in band addressing.
+We can use a 7 bit addressing to distinguish every device, but some address is reserved for the internal communication of the Helios64 board.
+
+#### I2C at UEXT
+
+The I2C header bus also can be found at UEXT connector (can be found at **P2** header at the the board [overview](/helios64/hardware/overview) page) on the header number 5 and 6.
+Below is the detail description of the UEXT connector:
+
+![I2C at UEXT](/helios64/img/i2c/UEXT_pinout.png)
+
+Pin No  | Description 
+--------|-------------
+1|3.3V
+2|GND
+3|TXD (UART)
+4|RXD (UART)
+5|SCL (I2C)
+6|SDA (I2C)
+7|MISO (SPI)
+8|MOSI (SPI)
+9|SCK (SPI)
+10|SSEL (SPI)
+
+Please take caution of the reserved address when you use the I2C interface, below is the reseved address list:
+
+Slave Address |	R/W Bit |	Description
+--------------|---------|-------------------
+000 0000 |	0  |	General call address
+000 0000 |	1  |	START byte(1)
+000 0001 |	X  |	CBUS address(2)
+000 0010 |	X  |	Reserved for different bus format (3)
+000 0011 |	X  |	Reserved for future purposes
+000 01XX |	X  |	Hs-mode master code
+111 10XX |	X  |	10-bit slave addressing
+111 11XX |	X  |	Reserved for future purposes
+
+
+### Usage under Linux
+
+#### External bus block device under linux
+
+Below table describe the external bus of I2C under Linux,
+
+Bus number | Device Block | Description  | 
+-----------|--------------|--------------|
+ 7         | /dev/i2c-0   |              |
+ 8         | /dev/i2c-1   |              |
+
+
+#### Checking the I2C Communication under linux
+
+In order to communicate with the I2C devices, first we need to identify the I2C bus.
+By performing scan you can see wether system detect the devices.
+
+We can follow this step to perform the scanning process:
 
 1. Install the Linux i2c tools.
 
@@ -24,4 +142,9 @@ root@helios64:~# i2cdetect -y 1
 70: -- -- -- -- -- -- -- --   
 ```
 
-Here we can see there is a device detected at the address 0x3c. We can conclude is our OLED screen, unless you have connected more than just one I2C device on the **J9** header.
+Here we can see there is a device detected at the address 0x3c. We can conclude is our OLED screen, unless you have connected more than just one I2C device on the **J9** header.  
+
+
+#### Application example
+
+We have demonstrated the use of I2C bus of our board in the OLED application, as shown in the [I2C(OLED)](/helios4/i2c/)  page you can communicate to the external device by using the external I2C bus.
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