====== Introduction U3 I/O shield on ubuntu ======
{{http://dn.odroid.com/homebackup/U3IOShieldR03AS.jpg?300|}}

The ODROID-U3 I/O Shield board can be plugged on the neat of ODROID-U3 via tiny 8 pin and 4 pin IO connector.\\
The shape and dimension are exactly same as ODROID-U3. It comes with 12pcs of PCB spacers for easier and solid stacking assembly.\\
The IO shield has 3 blocks. 
  * I2C IO expansion block
  * Arduino Compatible block
  * SPI Interface block(ODROID-U3+ and I/O shield Rev_0.3 or later)

[[http://www.hardkernel.com/main/products/prdt_info.php?g_code=G138760240354|Where to buy]]
===== I2C IO expansion block =====

TI's TCA6416A I2C to Parallel Port Expander is used in this block.\\
The major benefit of this device is its wide VCC range.\\
It can operate from 1.65 V to 5.5 V on the P-port side and on the SDA/SCL side separately.\\
It allows bidirectional voltage-level translation GPIO Expansion between 1.8V SCL/SDA(VCCI) and 5Volt Port(VCCP).\\

== Access GPIO from linux user space. ==
Standard Linux kernel have inside a special interface allow to access to GPIO pins.

1. Need to super-user permition
<code>
sudo su
[sudo] password for odroid : odroid
</code>

2. Load the kernel modules
<code>
modprobe i2c-gpio-custom bus0=4,200,199
modprobe gpio-pca953x
</code>

3. Set the I2C address of the module
<code>
echo tca6416 0x20 > /sys/devices/platform/i2c-gpio.4/i2c-4/new_device 
</code>

4. Enable GPIO's on the board.\\
**If Kernel version is higher than 3.8.13.30 gpio_n = 341 ~ 356**\\
else Kernel version is older than 3.8.13.30 gpio_n = 289 ~ 304\\

<code>
echo NUM > /sys/class/gpio/export
cd  /sys/class/gpio/gpioNUM
echo out > direction
echo 1 > value
echo 0 > value
</code>

===== Arduino Compatible block =====
Atmel’s ATmega328P is used as a slave CPU to expand the IO port. \\
You can use the Arduino IDE on ODROID-U3 to build & upload your sketches to this Arduino-compatible block, \\
without additional/external cable connections.\\
Like the Arduino Uno, it has 14 digital input/output pins (of which 6 can be used as PWM outputs), \\
6 analog inputs which provides 10 bits of resolution. They operate at 5 volts range.\\


===== SPI Interface block(ODROID-U3+ and I/O shield Rev_0.3 or later) =====